DRUGS AND SUPPLEMENTS

L-Carnitine

March 22, 2017

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L-carnitine

Natural Standard Bottom Line Monograph, Copyright © 2013 (www.naturalstandard.com). Commercial distribution prohibited. This monograph is intended for informational purposes only, and should not be interpreted as specific medical advice. You should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

While some complementary and alternative techniques have been studied scientifically, high-quality data regarding safety, effectiveness, and mechanism of action are limited or controversial for most therapies. Whenever possible, it is recommended that practitioners be licensed by a recognized professional organization that adheres to clearly published standards. In addition, before starting a new technique or engaging a practitioner, it is recommended that patients speak with their primary healthcare provider(s). Potential benefits, risks (including financial costs), and alternatives should be carefully considered. The below monograph is designed to provide historical background and an overview of clinically-oriented research, and neither advocates for or against the use of a particular therapy.

Related Terms

  • AcCn, acetyl-L-carnitine, B (t) Factor, beta-hydroxy-gamma-N-trimethylamino butyrate, canitor, Carnilean®, carnitene, carnitor, D-carnitine, D,L-carnitine, glycine propionyl-L-carnitine (GPLC), Godex®, L-3-hydroxytrimethylamminobutanoate, LAC, L-acetyL-carnitine, LCLT, L-CARNIPURE, L-Carnipure®, L-carnitina (Spanish), L-carnitine L-tartrate, levacecarnine, levocarnitine, levocarnitine chloride, LK-80, L-propionylcarnitine, propionil-L-carnitine, propionyl-L-carnitine, ST200, ST261, VitaCarn®, vitamin B(t), vitamin Bt.

  • Selected combination product: PhenCal (phenylalanine, tryptophan, glutamine, pyridoxal-5'-phosphate, chromium picolinate, carnitine).

  • Note: This monograph focuses on supplemental sources of carnitine (including acetyl-L-carnitine and propionyl-L-carnitine) and not the acyl (fatty acid) derivatives of carnitine made in the body upon metabolism of carnitine. Unless otherwise stipulated, the use of the term carnitine in this monograph implies the levo (l) carnitine and not d-carnitine, which may cause secondary deficiency.

Background

  • The main function of L-carnitine is to transfer certain fat-soluble molecules in the body across membranes within cells so the molecules can be broken down and used in the Krebs cycle. In humans, L-carnitine is synthesized in the liver, kidney, and brain and actively transported to other areas of the body. For example, 98% of the total body L-carnitine is confined to the skeletal and cardiac muscle at concentrations approximately 70 times higher than in the blood serum.

  • Supplementation may be necessary in rare cases of primary carnitine deficiency, which may be caused by a defect in the body's production of carnitine, a defect in the transport of carnitine into tissue, or a defect the kidney's ability to conserve carnitine. L-carnitine was shown to be effective in the following conditions which arise from secondary deficiency of L-carnitine: chronic stable angina (chest pain) and intermittent claudication (impaired walking or limping) characterized by low oxygen levels in tissues. Another condition that may benefit from carnitine supplementation is decreased sperm movement. Carnitine supplementation, as L-carnitine, or acetyl- or propionyl-L-carnitine, has been investigated in many other diseases and conditions.

  • Although use in preterm infants suggests that carnitine supplementation may aid in maintaining or increasing plasma carnitine levels and possibly weight gain, carnitine is not routinely added to preterm total parenteral nutrition (TPN). However, soy-based infant formulas are fortified with carnitine to levels found in breast milk.

  • In 1986, the U.S. Food and Drug Administration (FDA) approved L-carnitine for use in primary carnitine deficiency. However, D-carnitine or DL-carnitine may cause secondary L-carnitine deficiency and should not be used.

Scientific Evidence

Uses

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Grade*

Metabolic abnormalities (inborn errors of metabolism related to carnitine metabolism)

Various inborn errors of metabolism related to carnitine metabolism exist, including genetic disorders related to carnitine-acylcarnitine translocase deficiency. Evidence suggests that carnitine may be used as part of a treatment plan for carnitine-acylcarnitine translocase deficiency, as well as for the management of general inborn errors of metabolism and carnitine uptake defects.

A

Nutritional deficiencies (primary and secondary carnitine deficiency in adults)

Primary carnitine deficiency is an extremely rare genetic condition. Secondary deficiency is a deficiency in carnitine due to other factors. Evidence from case reports and reviews suggests that carnitine, given by mouth or injected into a vein, may used as part of a treatment plan for primary deficiency and various types of secondary deficiencies.

A

Peripheral vascular disease (blocked arteries in the legs)

Well-designed studies indicate that propionyl-L-carnitine and L-carnitine may be beneficial for the treatment of blocked arteries in the legs, especially in those cases when there are severe limitations in peripheral circulation. It is not clear, however, whether angiopathies (blood vessel diseases) caused by atherosclerosis (hardening of the arteries) or diabetes are equally sensitive to the carnitine agents.

A

Angina (long-term chest pain from clogged heart arteries)

Evidence from well-designed clinical trials suggests that L-carnitine and propionyl-L-carnitine are effective in reducing symptoms of chest pain due to clogged heart arteries. Possible increases in exercise tolerability have also been suggested as a result. Carnitine may not offer further benefit when patients continue conventional therapies. More high-quality studies are needed before a firm conclusion can be made.

B

Autism

Evidence from well-designed studies and reviews indicates that carnitine may offer benefit for individuals with autism. Further research is required before conclusions can be made.

B

Dialysis (hemodialysis)

Good evidence suggests that, for hemodialysis patients, carnitine given by mouth may increase levels of carnitine in the blood, enhance red blood cell survival, reduce heart or inflammatory disease risk factors, and improve quality of life. However, further research is required to understand the specific areas of benefit in this population.

B

Hepatic encephalopathy (confused thinking due to liver disorder)

Evidence from well-designed trials suggests that L-carnitine may improve the quality of life and mental functioning of individuals with confused thinking due to liver disorders. Further well-designed research is required in order to determine optimal dose and timing. Also, the evidence is limited by the majority of studies being conducted by the same research group.

B

Infertility (male)

Evidence from well-designed trials, systematic reviews, and meta-analyses suggests that carnitine and/or acetyl-L-carnitine may increase sperm movement and pregnancy rates. Further information is required with respect to dosing and duration, as well as the type of male infertility most likely to be benefited.

B

ADHD

Limited research has examined the effects of L-carnitine in boys with attention-deficit hyperactivity disorder (ADHD). Although results were promising, well-designed trials are needed before conclusions can be made. Furthermore, other research has indicated that cotreatment with carnitine and conventional ADHD treatment (methylphenidate) lacks additional benefit over conventional treatment alone.

C

Aging

Carnitine may alter body composition, decrease fatigue, and improve physical and mental functioning in individuals over 100 years of age. However, further research is required in this field.

C

AIDS

Limited evidence suggests that carnitine may increase proliferation of mononuclear cells and increase in CD4 counts in patients experiencing acquired immune deficiency syndrome (AIDS). However, the effect of carnitine on body fat and lipid (fat) levels associated with antiretroviral drugs was mixed. In order for conclusions to be made, well-designed studies are needed.

C

Alcoholism

Clinical trials suggest that L-carnitine or acetyl-L-carnitine may be of benefit to alcoholics. Well-designed clinical trials are required before conclusions can be made in this field.

C

Alertness

Limited evidence suggests that a combination product containing acetyl-L-carnitine can aid alertness in college students. Further research is required.

C

Alopecia (hair loss)

In limited research, carnitine increased hair growth in individuals with mild-to-moderate androgenetic alopecia (male-pattern baldness). Further well-reported research is required before conclusions can be drawn.

C

Alzheimer's disease

Results from early studies suggested that L-carnitine and/or acetyl-L-carnitine may be beneficial for Alzheimer's disease. Also, a combination product containing acetyl-L-carnitine, vitamins B12 and E, and other compounds significantly delayed mental decline (based on the Dementia Rating Scale), and improved behavioral symptoms (based on the Neuropsychiatric Inventory) and maintenance of performance. However, conflicting results exist. Better-designed clinical trials are required before conclusions can be made in this field.

C

Amenorrhea (lack of menstrual period)

Although preliminary results are promising, there is a lack of well-designed and reported clinical trials investigating the effect of L-carnitine on amenorrhea (the lack of menstruation). Well-designed and reported clinical trials are required before conclusions can be made.

C

Arrhythmia (abnormal heart rhythm)

Although preliminary results are promising, there is a lack of well-designed and reported clinical trials investigating the effect of L-carnitine on arrhythmia (abnormal heart rhythm). Well-designed and reported clinical trials are required before conclusions can be made.

C

Arthritis

Limited evidence suggests that carnitine may offer benefit for childhood psoriatic onycho-pachydermo-periostitis (POPP; a subset of psoriatic arthritis). Further research is required before conclusions can be made.

C

Beta-thalassemia (fewer red blood cells and less hemoglobin)

Carnitine may increase the effectiveness of hydroxyurea therapy in patients with beta-thalassemia intermedia. Although there is some evidence of benefit in these patients with carnitine alone, the endpoints are diverse and the quality of publication is poor. Therefore, the effect of carnitine alone is not clear, and further research with specific endpoints is required before conclusions can be made.

C

Brain injuries

Limited evidence indicates that acetyl-L-carnitine, used in combination with weight loss, vitamins, antioxidants, and nutrients to enhance blood flow, may improve sports-related brain injuries. In addition, carnitine injected into the vein may promote awakening from comatose thyroid storm. However, the effect of carnitine alone is not clear, and further research is required before conclusions can be made.

C

Cachexia (weight loss/wasting from some diseases)

Limited evidence suggests that carnitine had a lack of effect on fatigue, energy expenditure, and lean body mass in patients with cachexia due to cancer. Further research is required before conclusions can be made.

C

Cancer

Limited studies have evaluated carnitine as part of a treatment plan for pancreatic cancer and a certain type of advanced thyroid cancer. The effect of carnitine alone is not clear, and further research is required before conclusions can be made.

C

Cardiovascular disease (heart disease)

Limited evidence suggests that, in patients with heart disease, carnitine in combination with other agents, such as fasudil, may improve blood pressure levels. However, further research is required.

C

Cardiovascular disease risk

Limited evidence indicates that, in healthy individuals and individuals with type 2 diabetes, carnitine may reduce levels of cardiovascular disease risk factors. However, further research is required.

C

Cerebral ischemia (a lack of adequate blood flow to the brain)

A limited number of studies have shown a positive effect of acetyl-L-carnitine on blood flow to the brain and metabolism of the brain in patients who have suffered from stroke. Well-designed clinical trials are required before conclusions can be made.

C

Chronic fatigue syndrome

Preliminary evidence suggests a potential benefit from carnitine in patients with chronic fatigue syndrome, due to an altered metabolism of acyl-carnitine in these individuals. Well-designed clinical trials are required before conclusions can be drawn.

C

Dementia (elderly)

Most of the studies related to dementia suffer from various weaknesses. Although preliminary evidence is promising, there is currently inadequate evidence to conclude for or against the use of acetyl-L-carnitine for dementia. Well-designed clinical trials are required before conclusions can be made.

C

Depression

Although the limited results are promising, there is insufficient evidence to support the use of carnitine in the treatment of depression. Well-designed clinical trials with adequate subject numbers are required.

C

Diabetes mellitus

Limited evidence suggests that constant infusion of L-carnitine may increase insulin sensitivity in patients with type 2 diabetes mellitus and enhance glucose (sugar) oxidation. These results need to be confirmed in long-term studies. Some studies suggest that carnitine may decrease fasting blood glucose and lipoprotein levels, but results are not consistent. Well-designed clinical trials are still required before firm conclusions can be made.

C

Diabetic nerve damage (neuropathy)

Preliminary evidence suggests that acetyl-L-carnitine may be beneficial for individuals with diabetic nerve damage. However, more well-designed clinical trials are required before conclusions can be made.

C

Dialysis (CAPD)

Limited research has investigated the effect of L-carnitine in patients receiving continuous ambulatory peritoneal dialysis (CAPD). A beneficial effect of carnitine on hypertriglyceridemia (increased levels of fatty compounds that are associated with blood vessel hardening) was lacking. Better-designed clinical trials are required before conclusions can be made.

C

Diphtheria (throat disease)

Preliminary evidence suggests that carnitine may reduce heart muscle damage in patients with diphtheria (a certain throat disease). However, more well-designed trials should be performed to confirm these results.

C

Down's syndrome

Preliminary evidence suggests that acetyl-L-carnitine may not be beneficial for patients with Down syndrome. Additional well-designed trials are required.

C

Drug withdrawal

Preliminary evidence suggests that acetyl-L-carnitine may be beneficial for withdrawal from opiates. Additional well-designed trials are required.

C

Elimination of toxins (drugs)

Limited evidence suggests that carnitine may be used as part of a treatment plan for toxicity associated with various drugs. For instance, carnitine may reduce valproate-induced liver injury. In addition, acetyl-L-carnitine may reduce HIV-associated antiretroviral toxic nerve damage. The effect of carnitine on chemotherapeutic toxicity has also been examined, but conclusions cannot be drawn at this time. Additional well-designed studies are needed.

C

Erectile dysfunction

Preliminary studies suggest that propionyl-L-carnitine, with acetyl-L-carnitine or sildenafil, may be beneficial for patients with erectile dysfunction (ED). However, more rigorous trials should be performed to determine the effectiveness of carnitine for routine use in ED.

C

Exercise performance

Overall, the data are mixed in terms of benefits of L-carnitine for exercise performance. Until confirmed, the advisability of use of L-carnitine for increased exercise endurance is unclear.

C

Fatigue

Some evidence suggests that L-carnitine may be an effective treatment for fatigue. However, due to the different populations studied, it is difficult to draw conclusions. Well-designed clinical trials are required in specific populations before conclusions can be made.

C

Fibromyalgia (long-term musculoskeletal disorder)

Limited evidence suggests that L-carnitine may be a beneficial treatment for the long-term musculoskeletal disorder called fibromyalgia. Further research is required.

C

Fragile-X syndrome

There is insufficient evidence to support the use of carnitine in the treatment of hyperactive behavior of children with fragile-X syndrome. Further well-designed clinical trials are still required.

C

Heart failure (CHF)

Despite strong evidence in animal and human studies that congestive heart disease is associated with reduced levels of carnitine in heart muscles, the number of well-organized studies demonstrating the efficacy of carnitine supplementation is small. Further well-designed clinical trials are required before conclusions can be made.

C

Huntington's chorea/disease

Limited evidence suggests that acetyl-L-carnitine possesses neither efficacy nor toxicity towards the patients with Huntington disease. Further trials are required before conclusions can be made.

C

Hyperlipoproteinemia (high levels of lipoprotein and cholesterol in the blood)

Although preliminary evidence is promising, well-designed clinical trials are still required to determine the beneficial effect of carnitine on hyperlipoproteinemia (high levels of cholesterol in the blood).

C

Hyperthyroidism (overactive thyroid)

Limited evidence indicates that carnitine may have beneficial effects on symptoms associated with hyperthyroidism (an overactive thyroids). However, currently there is not enough evidence to determine the use of carnitine as a treatment for this condition.

C

Lactic acidosis (lactic acid buildup)

There are a limited number of studies relevant to the use of carnitine for lactic acidosis (lactic acid buildup). There is not sufficient evidence to make a conclusion for the use of carnitine for this condition.

C

Liver disease

There are a limited number of studies relevant to the use of carnitine for liver disease. Some early promising results were obtained, but there is not sufficient evidence to make a conclusion for the use of carnitine in the treatment of liver cirrhosis.

C

Memory

There are a limited number of studies relevant to the use of carnitine for memory. However, carnitine's use lacked effect unless taken with a glucose drink; the glucose drink alone also appeared to be beneficial. Thus, more trials are required in this field before conclusions can be made.

C

Metabolic abnormalities

Carnitine has been used as part of a treatment regimen in pregnant women with metabolic abnormalities such as methylmalonic acidemia (MMA) and cobalamin C (cblC) deficiency, methylmalonic acidemias and acidurias, and isovaleric academia, as well as in siblings or infants with a mutation of methylmalonyl-CoA mutase gene, and propionic academia (PA). However, the benefits are still unclear, and further studies are needed.

C

Mitochondrial disorders

Carnitine has been used as part of a treatment plan for various mitochondrial disorders. The use of carnitine for genetic mitochondrial disorders has been discussed by various authors. Further research is required due to the limited number of such disorders in existence.

C

Multiple sclerosis

Based on only limited research, there is inconclusive evidence that carnitine is helpful for multiple sclerosis (MS)-related fatigue. Further research is required.

C

Myocardial infarction (heart attack)

Limited evidence suggests a decline in the size of an infarction (heart attack) with carnitine treatment. Well-designed studies are needed to make conclusions on the use of L-carnitine for the treatment of acute infarction.

C

Nutritional deficiencies (adults)

Limited evidence suggests that the use of carnitine lacks an effect on the metabolism of lipid components of parenteral nutrition. Thus, currently there is insufficient evidence to support the use of carnitine in total parenteral nutrition (TPN) for adults.

C

Nutritional deficiencies (full-term infants)

It is not clear whether full-term infants receiving total parenteral nutrition (TPN) need additional carnitine. For long-term feeding with plant-derived proteins such as soy formula, carnitine may be added to levels found in breast milk. However, it is unclear what effect, if any, the addition of carnitine has on weight gain. Carnitine in TPN has offered mixed results, although increased carnitine status has been noted. Further studies are needed.

C

Nutritional deficiencies (premature infants)

Despite a large number of studies, it is not clear whether premature infants receiving total parenteral nutrition (TPN) need additional carnitine. Limited evidence suggests that additional carnitine may cause adverse effects in terms of weight gain. Thus, it is not advisable to use carnitine in TPN in low-birthweight infants, without evidence of need. For long-term feeding with plant-derived proteins such as soy formula, carnitine may be added to levels found in breast milk. However, It is unclear what effect, if any, the addition of carnitine has on weight gain. Further studies are needed.

C

Obesity

According to limited evidence, L-carnitine had a lack of effect on weight loss in obese patients. Further studies are needed before conclusions can be made.

C

Peripheral neuropathy (pain in hands and feet due to nerve damage)

Currently there is not sufficient evidence to make conclusions for the use of carnitine as a treatment for peripheral neuropathy (pain in the hands and feet due to nerve damage). Further studies are needed.

C

Peyronie's disease

Promising results have been reported for the use of carnitine in individuals with Peyronie's disease. However, further studies are needed to confirm these results.

C

Pregnancy (miscarriage)

Limited research has investigated carnitine for threatened miscarriage. However, the sample size was too small to make conclusions. Well-designed clinical trials are needed in this field.

C

Respiratory distress (adults)

Limited research has examined carnitine for respiratory distress in adults. As yet, there is insufficient evidence to use carnitine for this condition.

C

Respiratory distress (infants)

Limited research has investigated the use of carnitine for respiratory distress in infants. Currently there is not sufficient evidence to support the use of carnitine for this condition.

C

Rett's syndrome

Limited studies have shown promising results for the use of carnitine for treating Rett syndrome. Before strong conclusions can be made, additional well-designed trials are required.

C

Sciatica (back and leg pain)

According to limited evidence, acetyl-L-carnitine may reduce the sciatic pain due to a herniated disc. Further well-reported research is required before conclusions may be drawn.

C

Sickle cell disease

Preliminary evidence suggests the absence of any therapeutic effect of propionyl-L-carnitine for sickle cell disease. Additional studies are required before conclusions can be made.

C

Surgical uses (bypass)

The results of studies on the use of carnitine in improving the functioning of the myocardium (heart's muscular tissue) during open-heart surgery are controversial. Currently, there is not enough evidence to make conclusions for the use of carnitine as a treatment for this condition.

C

Systemic lupus erythematosus (SLE, or lupus)

Limited evidence is available with respect to carnitine for systemic lupus erythematosus. Further research is required.

C

Tuberculosis

Limited evidence suggests that antibacterial activity may be increased in patients with tuberculosus given acetyl-L-carnitine. Well-designed clinical trials are required before conclusions can be made.

C

*Key to grades:A: Strong scientific evidence for this use; B: Good scientific evidence for this use; C: Unclear scientific evidence for this use; D: Fair scientific evidence against this use (it may not work); F: Strong scientific evidence against this use (it likely does not work).

Tradition/Theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious and should be evaluated by a qualified health care professional.

  • Acne, amyotrophic lateral sclerosis (ALS), anorexia, antioxidant, appetite stimulant, ataxia (ataxia telangiectasia; uncoordinated movements and enlarged blood vessels), blood circulation, blood disorders (uremia), cancer (carnitine deficiency), chronic obstructive pulmonary disease (long-term lung disease), cocaine withdrawal, cognition (mental processes), diabetic ketoacidosis (methylmalonic acidemia mimicking diabetic ketoacidosis, or high levels of acids in the blood associated with diabetes), dizziness, dry eyes, encephalopathy (various causes or brain disease or damage), fatigue in cancer patients, gonarthrosis (chronic wear of cartilage in knee joints), hepatitis (viral-associated fatigue), hypertension (high blood pressure), immune function (hyper-IgE syndrome), immunomodulator, inborn errors of urea synthesis (urea cycle disorders), kidney disease, macular degeneration (eye diseases), male infertility (idiopathic oligoasthenoteratozoospermia), metabolic abnormalities (propionate), metabolic disorders (acquired total lipodystrophy), metabolic disorders (various), mitochondrial disorders (changes due to aging and obesity), muscle and joint disorders (rhabdomyolysis), muscle pain, muscle weakness (aging), myocarditis/endocarditis (heart infections), myopathy (metabolic muscular disease), neurodegenerative disorders (nervous tissue disease), neurologic disorders (children), ocular disorders (eye disorders), organ transplantation (liver), pain, Parkinson's disease, proteinuria (lysinuric protein intolerance), psychiatric disorders, pulmonary function (muscle strength related to inhaling in those with type 2 diabetes), retinal protection, retinitis pigmentosa (eye disease), seizure disorders, skin conditions (dystrophic epidermolysis bullosa or skin blister formation), tired eyes, tinnitus (ringing in the ears), ulcerative colitis (inflammatory bowel disease), vitamin B12 deficiency (carnitine restriction).

Dosing

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Adults (18 years and older)

  • The U.S. Food and Drug Administration (FDA) recommends one gram of L-carnitine three times daily, intravenously (injected), for primary and secondary carnitine deficiency. This dose should not exceed three grams daily. Approximately 0.25-12 grams of carnitine (L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine) or 10-100 milligrams of carnitine per kilogram of body weight has been given by mouth 1-3 times daily, with 1-3 grams daily being the most common dose. Treatments have lasted for one week to 54 months. Single doses up to 15 grams have been given by mouth.

  • Carnitine has been taken by mouth to treat conditions including abstinence from alcohol (for alcoholics), aging, AIDS, Alzheimer's disease, amenorrhea (lack of menstrual period), angina (chest pain), antiretroviral toxic neuropathy (nerve damage), autism, cachexia (disease-induced weight loss), cardioprotection (protection of the heart) from chemotherapy agents, cardiovascular disease (heart disease) risk, chronic fatigue, congestive heart failure, depression, diabetes, diabetic neuropathy (nerve damage), dialysis (CAPD), Down syndrome, exercise performance, fatigue and depression associated with cancer, fatigue (celiac), fatigue (general), fatty liver disease, fibromyalgia, fragile-X syndrome, hepatic encephalopathy (confused thinking due to liver disorders), HIV, hyperlipidemia (high cholesterol), hyperthyroidism (overactive thyroid), infertility (male), insulin sensitivity, liver disease, medium-chain acyl-CoA dehydrogenase deficiency (MCAD), memory (in alcoholics), methadone withdrawal, multiple sclerosis, myocardial infarction (heart attack), obesity, peripheral neuropathy (nerve damage), peripheral neuropathy caused by chemotherapy, peripheral vascular disease, Peyronie's disease, pregnancy (miscarriage), primary and secondary carnitine deficiency, respiratory distress, Rett syndrome, sciatica, sickle cell disease, thalassemia, and varicocele (a widening of the veins along the cord that holds up a man's testicles), as well as for surgical uses (bypass).

  • For hair growth, a 2% carnitine solution has been applied to the scalp twice daily for six months.

  • Intravenous injections have also been used, with doses ranging from 10 to 100 milligrams per kilogram of body weight or 0.3-9 grams daily. Injections have been given for a duration of three days up to one year. Intramuscular injections have also been used, with doses typically being one gram of carnitine daily for 14-24 days. Injections should only be given under the supervision of a qualified healthcare professional, including a pharmacist.

  • Carnitine has been injected into the veins or muscle to treat conditions including alcoholism (abstinence), angina (long-term chest pain from clogged heart arteries), cardiovascular disease (heart disease) risk, cerebral ischemia (a lack of adequate blood flow to the brain), congestive heart failure, diabetic neuropathy (nerve damage), dialysis (CAPD), exercise performance enhancement, fibromyalgia, hepatic encephalopathy (confused thinking due to liver disorders), myocardial infarction (heart attack), peripheral neuropathy (numbness and pain in hands and feet caused by nerve damage), peripheral vascular disease (blocked arteries in the legs), primary and secondary carnitine deficiency, surgical uses (bypass), and valproic acid toxicity.

  • Parenteral doses of carnitine are determined for individuals based on stages of the life cycle and affected organs. Doses of 2-5 milligrams of carnitine per kilogram of body weight are given daily by the route used for the administration of macronutrients. Some sources suggest that pharmacologic supplementation should be 50-100 milligrams per kilogram of body weight daily.

Children (under 18 years old)

  • For attention-deficit hyperactivity disorder (ADHD), 500-1,500 milligrams of acetyl-L-carnitine has been given for 16 weeks.

  • For dialysis, 20 milligrams of carnitine per kilogram of body weight has been given by mouth daily for three months. L-Carnitine (50 milligrams per kilogram of body weight) has been given by mouth daily for two months.

  • For enteral use (in infants), 50 micromoles of carnitine per kilogram of body weight has been given through a gastric or nasogastric tube daily for seven days.

  • For hyperlipidemia (high cholesterol), three grams of L-carnitine has been given for up to six weeks.

  • For premature infants, 20 milligrams of carnitine per kilogram of body weight has been given daily by dosing the parenteral solutions with 130 milligrams of L-carnitine (Carnitor®, Sigma Tau Pharmaceuticals, Gaithersburg, MD) per liter and administering the supplemented PN solution at an infusion rate of 150 milliliters per kilogram of body weight. Also, 20 milligrams of L-carnitine (Carnitor®, Sigma Tau Pharmaceuticals, Gaithersburg, MD) per kilogram of body weight has been added to Pregestimil®, Nutramigen®, or Enfamil Premature® (Mead Johnson Nutritionals, Evansville, IN) formulas or expressed human milk daily for up to eight weeks.

  • For primary and secondary carnitine deficiency, 100-200 milligrams of carnitine per kilogram of body weight has been given by mouth daily over two or three doses. The U.S. Food and Drug Administration (FDA) does not recommend exceeding three grams of carnitine daily for primary and secondary carnitine deficiency.

  • For respiratory distress, 30 milligrams of L-carnitine per kilogram of body weight has been given daily in TPN until 120 milliliters per kilogram of body weight daily of enteral feedings were tolerated. Then 30 milligrams of carnitine per kilogram of body weight has been given by mouth daily.

  • For Rett syndrome, 100 milligrams of carnitine per kilogram of body weight has been given three times daily.

  • For total parenteral nutrition (TPN) for infants, 50 micromoles of carnitine per kilogram of body weight has been given daily for two weeks. Also, 10 milligrams of carnitine (L-carn®, Ildong Pharmaceutical Co Ltd, Seoul, Korea) per kilogram of body weight has been given for nine days.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

  • Avoid in individuals with a known allergy or sensitivity to carnitine.

Side Effects and Warnings

  • In general, L-carnitine is safe, and no significant complications have been reported in available human clinical studies. However, individuals must be sure to use only L-carnitine preparations with ≥99% enantiomeric purity.

  • Minor adverse effects reported by people have included abdominal cramping, abdominal discomfort, aggression, anxiety, back pain, bilateral ptosis (drooping eyelids), body odor, colitis symptoms, constipation, depression, diarrhea, euphoria, facial paresthesia (abnormal sensations), fatigue, fatigue in chewing, "fishy smell," gastralgia (stomach pain), gastric pyrosis (heartburn), gastrointestinal (stomach and intestinal) symptoms, headache, insomnia, loose bowel movements, low birthweights, mania, nausea, nervousness, psychosis, skin rashes, temporary hair loss, vomiting, and weakness. Serious adverse effects reported by people have included bronchitis, chronic obstructive pulmonary disease (long-term lung disease), and pulmonary embolism (blot clots in the lungs).

  • According to animal studies, carnitine may also cause endometriosis (growth of endometrial tissue outside the uterus), infertility, reduced heart contracture after a heart attack, and a slower heart rate increase after a heart attack,

  • When applied to the skin, carnitine may cause a burning sensation, increased dandruff, itching, and reddish bumps.

  • Carnitine may cause high blood pressure, although animal studies have also indicated that carnitine may cause low blood pressure. Caution is advised in people taking drugs, herbs, or supplements to lower blood pressure, as carnitine may affect these agents.

  • Carnitine may lower blood sugar levels. Caution is advised in people with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Blood glucose levels may need to be monitored by a qualified healthcare professional, including a pharmacist, and medication adjustments may be necessary.

  • Use cautiously in patients with alcohol-induced liver cirrhosis (liver disease), gastroesophageal reflux disease (GERD), insomnia, irritable bowel syndrome (IBS), long-term hepatitis C, mental illness or a risk of mental illness, narcolepsy, peripheral vascular disease (blocked arteries in the legs), preexisting gastrointestinal (stomach and intestinal) conditions, respiratory (breathing) disorders, or sleeping disorders, as well as in women and those on hemodialysis.

  • Use cautiously in patients taking anticoagulants, beta-blockers, or calcium channel blockers.

  • Use cautiously in low-birthweight infants due to potential for decreased weight gain. Individuals should make sure that L-carnitine prescribed to neonates (newborns) is justified and appropriate.

  • Avoid using in women who are pregnant or lactating, as well as in children.

  • Avoid using with D- or DL-carnitine.

Pregnancy and Breastfeeding

  • In pregnant women, carnitine may cause reduced levels of certain enzymes, free fatty acids, certain proteins, and triglycerides. Also carnitine may cause increased levels of carnitine and carnitine derivatives in the umbilical cord. Carnitine levels may be lower for pregnant women with gestational diabetes. Pregnant women with 3-methylcrotonyl-CoA carboxylase deficiency (3-MCC) deficiency may give birth to infants with increased levels of a certain form of carnitine.

  • In infertile men, carnitine may cause increased sperm motility and levels of seminal carnitine.

  • In preterm infants with respiratory distress syndrome, serum carnitine levels may be decreased. In newborns with isovaleric academia, carnitine levels may be increased.

  • In human infants, plasma free carnitine levels may be lowest for breastfed infants vs. formula-fed or mixed-fed groups.

  • In children with nonsyndromic cleft lip with or without cleft palate, malonyl-carnitine and acetyl-carnitine may be decreased.

  • Although the topic has not been well studied in humans, carnitine may cause the development of parthenogenetic embryos, endometriosis (growth of endometrial tissue outside the uterus), increased chorion weight and DNA/protein content, increased oocyte development and maturation, and infertility. Also, carnitine may influence growth catch-up rate after intrauterine growth restriction. L-carnitine consumption during pregnancy may improve the suckling behavior and weight gain of offspring.

  • Although the topic has not been well studied in humans, the level of carnitine in lactated milk may be affected by the presence of a protein called the OCTN transporter. Also, lactation may reduce levels of certain receptor proteins in the liver, which reduces carnitine production.

  • Although the topic has not been well studied in humans, L-carnitine may reduce the negative effects of oxidative stress on ovaries, oocytes, and embryos.

  • Although the topic has not been well studied in humans, L-carnitine may reduce the development of metabolic disorders during lactation.

  • Although the topic has not been well studied in humans, increased carnitine consumption by a pregnant individual may increase carnitine levels in the newborn, the offspring's birthweight, and growth during suckling. Increased consumption of carnitine and other herbs may improve the formation of the lining of the small intestines in neonates (newborns), although the effect of carnitine alone is unclear.

  • According to cell culture studies, carnitine uptake in human cells that provide nutrients to embryos may be reduced by lack of oxygen. Also, carnitine may increase the viability of maturing oocytes and affect the activity of certain enzymes, particularly those involved in antioxidant activity in premature neonates.

  • L-carnitine has been suggested as being an important nutrient during pregnancy.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

Interactions with Drugs

  • Carnitine may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.

  • Carnitine may interfere with the way the body processes certain drugs using the liver's cytochrome P450 enzyme system. As a result, the levels of these drugs may be decreased in the blood, and reduce the intended effects. People taking any medications should check the package insert and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.

  • Although the topic has not been well studied in humans, carnitine may affect blood pressure. Caution is advised in people taking medications that lower blood pressure.

  • Many drugs influence the levels of carnitine in the body. Adefovir dipivoxil, anticonvulsants (carbamazepine, phenobarbital, and phenytoin), cephalosporins, doxorubicin, erythropoietin, penicillin derivatives (pivalate-containing antibiotics), polypharmacy, and valproic acid have been associated with low levels of carnitine in the blood. Lymphoblastoid interferon-alpha treatment may increase carnitine levels in the blood. The anticancer agent doxorubicin may increase levels of carnitine in the blood, although carboplatin, cisplatin, ifosfamide, and oxaliplatin resulted in increased elimination of carnitine in the urine. Carnitine levels may also be affected by natalizumab.

  • Although the topic has not been well studied in humans, 2,3-dimercapto-1-propanesulfonic acid may reduce carnitine excretion in urine. Paracetamol (acetaminophen) may cause carnitine deficiency. Aristolochic acid, cefepime, gentamicin, mildronate, pivalic acid, tacrolimus, and tetradecylthioacetic acid (TTA) may reduce carnitine levels. 3,4-Methylenedioxymethamphetamine (MDMA; Ecstasy) and triheptanoin may increase carnitine levels. Carnitine levels may also be affected by clofibrate and propiconazole.

  • Carnitine may reduce the negative side effects of several medications. Acetyl-L-carnitine may reduce pain and other negative effects of anticancer agents, as well as nerve damage caused by anticancer (cisplatin, paclitaxel) and HIV drugs. Carnitine may reduce heart toxicity caused by bupivacaine; fatigue caused by cyclophosphamide, ifosfamide, and interferon-beta; and liver and muscular damage caused by isotretinoin. Carnitine may also reduce the negative side effects of interleukin-2 (IL-2) and zidovudine. Decreased levels of carnitine have been associated with increased nerve damage caused by nucleoside analogs. Although the topic has not been well studied in humans, carnitine may reduce various negative side effects caused by acetaminophen, Adriamycin, carboplatin, ceftriaxone, cisplatin, doxorubicin, gentamicin, indomethacin, irradiation therapy, kidney toxins, liver toxins, methamphetamine, oxaliplatin, paclitaxel, and tilmicosin.

  • When used in combination, carnitine may improve the effects of certain drugs. Carnitine may increase the effects of acetylcholinesterase (ACE) inhibitors, agents used to treat hepatitis C (alpha-interferons), azithromycin, digoxin, drugs that promote urination, erythropoietin, hydroxyurea, nipecotic acid, orlistat, phosphodiesterase type 5 inhibitors (for sexual dysfunction), propafenone, ribavirin, sildenafil, and simvastatin. Although the topic has not been well studied in humans, carnitine may improve the effects of drugs for stomach and intestinal discomfort, leupeptin, and painkillers.

  • Carnitine may interact with agents for angina (chest pain), anti-inflammatory agents, beta-blockers, betaine, calcium channel blockers, cholesterol-lowering agents, cinnoxicam, exercise performance agents, fertility agents, glycosides, hair-growth agents, heart rate-regulating agents, immunomodulating agents, insulin, phenazopyridine, and potassium chloride. Although the topic has not been well studied in humans, carnitine may interact with agents that affect hearing loss, agents that affect the heart and blood vessels, agents that affect the nerves, agents used to treat opioid overdoses, Alzheimer's agents, antidepressants, antiobesity agents, bone agents, fertility agents, memory agents, mitoxantrone, nortriptyline, ocular agents, radioactive iodine, tilisolol, and wound-healing agents.

  • Although the topic has not been well studied in humans or animals, carnitine may reduce the negative effects of amiodarone, Also, carnitine may improve the effects of cisplatin. Carnitine may interact with agents that cause blood vessel widening, epirubicin, fluoroquinolones, grepafloxacin, levamisole, levofloxacin, OCTN2 inhibitors, progesterone, respiratory (breathing) agents, and thyroid hormones.

Interactions with Herbs and Dietary Supplements

  • Carnitine may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.

  • Carnitine may interfere with the way the body processes certain herbs or supplements using the liver's cytochrome P450 enzyme system. As a result, the levels of other herbs or supplements may become too low in the blood. It may also alter the effects that other herbs or supplements potentially may have on the P450 system.

  • Carnitine may affect blood pressure. Caution is advised in people taking herbs or supplements that lower blood pressure.

  • Many herbs and supplements may influence the levels of carnitine in the body. Antibacterial herbs and supplements may decrease carnitine levels. Biotin, choline, and vitamin C may affect carnitine levels. Iron deficiency anemia may be associated with low carnitine levels. Vitamin B12 deficiency may cause increased carnitine levels.

  • Although the topic has not been well studied in humans, vitamin E (alpha-tocopherol) may increase carnitine levels. Lysine may reduce carnitine levels. Medium-chain triglycerides, sesame lignans, and stevia may affect carnitine levels.

  • Carnitine may reduce the negative side effects of several herbs and supplements. Carnitine may reduce the negative effects of antiviral herbs and supplements. Although the topic has not been well studied in humans, carnitine may reduce various negative side effects caused by branched-chain amino acids, copper, nickel,

  • Carnitine may interact with betaine, cholesterol-lowering herbs and supplements, exercise performance herbs and supplements, herbs and supplements that increase urination, herbs and supplements that prevent blood clotting or inflammation, immunomodulating herbs and supplements, licorice, mangosteen, and Wuzi Yanzong liquids.

  • Carnitine may interact with alpha-lipoic acid; antidepression herbs and supplements; antiobesity herbs and supplements; antioxidant herbs and supplements; arginine; biotin; caffeine; calcium; coenzyme Q10; fertility-enhancing herbs and supplements; fish oil; genistein; glycerophosphocholine; herbs and supplements that affect Alzheimer's disease, bone density, hearing, memory, the heart or blood vessels, the stomach or intestines, or vision; herbs and supplements that cause kidney damage, liver toxicity, or nerve damage; milk thistle; N-acetyl-cysteine; nicotinamide; painkillers; phosphatidylserine; S-adenosyl methionine; selenium; soy; St. John's wort; taurine; and wound-healing herbs and supplements.

  • Alpha-ketoglutarate may increase carnitine levels. Carnitine may interact with anticancer herbs and supplements, butyrate, conjugated linoleic acid (CLA), herbs and supplements that affect breathing, herbs and supplements that affect hair growth, lotus leaf extract, progesterone, and thyroid-influencing herbs and supplements.

Author Information

  • This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

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Copyright © 2013 Natural Standard (www.naturalstandard.com)

The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.

Updated:  

March 22, 2017