March 21, 2017


Other name(s):

a-amino-g-methylthiol-n-butyric acid


Methionine is an amino acid. You need it for protein synthesis and synthesis of other physiologic compounds.  

Unsubstantiated claims

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

Methionine is an antioxidant. It may help protect the body from damage caused by ionizing radiation and detoxify harmful substances in the body, such as heavy metals. It may also prevent liver damage in acetaminophen poisoning and inhibit fat deposition in your liver.

It may also help ease fatigue and reduce the risk of early balding. It may also be helpful in osteoporosis.

Recommended intake

Amino acids (AAs) are available as individual AAs or in AA combinations. They also come as part of multi-vitamins, proteins, and food supplements. The forms include tablets, fluids, and powders.

Note that by eating enough protein in your diet, you get all of the amino acids you need.

There are no conditions that increase how much methionine you need.

Side effects, toxicity, and interactions

Using a single amino acid supplement may lead to negative nitrogen balance. This can decrease how efficient your metabolism is. It can also make your kidneys work harder. In children, taking single amino acid supplements may also cause growth problems.

You should not take high doses of individual amino acids for long periods of time.

Methionine can cause nausea, vomiting, and dizziness. It can also cause drowsiness, low blood pressure, and irritability. It may also make liver problems worse. Talk to your healthcare provider before using it if you have severe liver disease.  

Women who are pregnant or breastfeeding shouldn’t use methionine supplements.

Toxicity of methionine is rare. It only happens if you take too much of it.

People with homocystinuria type I, an inherited disease, shouldn’t use methionine supplements.

If you take methionine supplements without enough folic acid, vitamin B6, and vitamin B12, it can increase the conversion of methionine to homocysteine. This may increase your risk for heart disease.




March 21, 2017


Overview of homocysteine. UpToDate.

Reviewed By:  

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