March 21, 2017


Other name(s):

vitamin B3, niacinamide, nicotinamide, nicotinic acid, nicotinic acid amide

General description

Niacin is a member of the B family of vitamins (B Complex). It’s a water-soluble vitamin. Excess amounts come out through the kidneys. Like the other B vitamins, niacin plays a role in energy production.

Niacin works in two enzyme systems (NAD and NADP). They affect all the tissues of the body. These enzyme systems help transport hydrogen within the cell. They also make it available for biosynthesis. These two enzymes also work closely with the energy molecule adenosine triphosphate (ATP).

Medically valid uses

Nicotinic acid or niacinamide are used to treat and prevent pellagra. This is a disease caused by niacin deficiency. Niacin is also used to treat high cholesterol. In some cases niacin, along with colestipol, can work as well as colestipol and a statin medicine to treat high cholesterol. These medicines include lovastatin, pravastatin, and simvastatin.

Unsubstantiated claims

Please note that this section reports on claims that have not yet been substantiated through studies.

Niacin may improve the health of the skin. It may also improve thyroid function and keep your digestive system healthy. It’s also said to treat the following:

  • Schizophrenia

  • Alcohol dependence

  • Hallucinations due to medicines

  • Leprosy

  • Motion sickness

  • Peripheral vascular disease

Recommended intake

How much niacin you need depends on how many calories you eat. You need about 4.4–6.6 mg of niacin for every 1,000 calories you eat.

Niacin is supplied in milligrams. The RDA is the Recommended Dietary Allowance.



Infants (0–6 months)

2 mg*

Infants (7 months to 1 year)

4 mg*

Children (1–3 years)

6 mg

Children (4–8 years)

8 mg

Children (9–13 years)

12 mg

Males (14–18 years)

16 mg

Females (14–18 years)

14 mg

Males (19 years and older)

16 mg

Females (19 years and older)

14 mg

Pregnant women

18 mg

Breast-feeding women

17 mg

*Adequate Intake (AI). This is based off the average intake in healthy, breastfed infants.

Take niacin with food. This can help reduce upset stomach. Don’t crush or open time-release forms.

Food source

Nutrient content per 100 grams

Dried yeast

37.9 mg

Roasted peanuts

17.1 mg

Peanut butter

15.7 mg

Beef liver

13.6 mg

Chicken liver

10.8 mg


7.7 mg

Brazil nuts

7.7 mg


7.5 mg


7.4 mg


6.5 mg

The amino acid tryptophan can be converted into niacin. Foods high in tryptophan may prevent niacin deficiencies. Examples include milk and eggs.

Niacin is stable in heat. It doesn’t need to be refrigerated. Only small amounts are lost in the cooking process.

You need more niacin if you have certain cancers, such as carcinoid. You may also need more if you have chronic diarrhea or if you drink a lot of alcohol.

Isoniazid is a medicine used to treat tuberculosis. It can cause pellagra. This is a niacin deficiency. If you’re taking this medicine, you’ll likely need to take niacin supplements.

Because cereals and grains have very little niacin, diets based on corn and corn flour (also low in tryptophan) may lead to pellagra.

Symptoms of pellagra include the following dark red, symmetrical blotches on the skin. These are more likely to appear on areas exposed to sunlight and open air. The skin becomes dry and cracked, with a brownish color. Other symptoms include inflammation of the lining of the mucous membranes (nose, mouth, throat, and vagina) and intestinal tract. They also include bloody diarrhea, confusion, delirium, and hallucinations.

Side effects, toxicity, and interactions

Niacin dilates the blood vessels in the skin, especially in the upper body. A dose of 100 mg taken on an empty stomach may cause flushing of the skin. This may also cause intense itching or burning. A sustained-release form doesn’t prevent flushing. It only delays it. Niacinamide doesn’t cause this effect. Niacinamide doesn’t affect the cardiovascular system or change lipid levels.

Niacin can cause liver damage when taken long-term at high doses over a long time. This is especially true for the sustained-release form.

Some forms of niacin contain tartrazine. If you’re allergic to aspirin, you may be sensitive to tartrazine. You should avoid forms that contain it. You shouldn’t take niacin without talking to your healthcare provider if you have liver problems or an active peptic ulcer.

If you’re pregnant, don’t take niacin supplements.

You shouldn’t take niacin if you’re taking lovastatin. Taking niacin with this medicine may lead to myolysis.

Nicotinic acid may keep sulfinpyrazone from being able to decrease uric acid levels. Niacin may also increase uric acid levels. If you have high uric acid levels or gout, talk to your healthcare provider before taking a niacin supplement.



March 21, 2017


Niacin. Merck Manuals.

Reviewed By:  

Poulson, Brittany, RD, CDE,Wilkins, Joanna, R.D., C.D.