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Other name(s):

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


Methionine is an essential amino acid. You need to get it through your diet. It's needed to make protein and other compounds in your body.  

Unsubstantiated claims

There may be benefits that have not yet been proven through research.

Methionine is an antioxidant. It may help protect the body from damage caused by ionizing radiation. It may detoxify harmful substances in the body. These include heavy metals. It may also prevent liver damage from acetaminophen poisoning and help prevent fat deposits in your liver.

It may also help ease fatigue and reduce the risk of early balding. Methionine may also help treat osteoporosis.

Recommended intake

Amino acids (AAs) can be taken as single AAs. Or in AA combinations. They also come as part of multivitamins, proteins, and food supplements. The forms include tablets, fluids, and powders.

You get all of the amino acids you need if you eat enough protein in your diet.

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 lessen how well your metabolism works. It can also make your kidneys work harder. In children, taking single amino acid supplements can lead to growth problems.

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

Methionine can cause:

  • Nausea

  • Vomiting

  • Dizziness

  • Drowsiness

  • Low blood pressure

  • Irritability

It may also make liver problems worse. Talk to your healthcare provider before using it if you have severe liver disease.  

People with bipolar disorder should not take methionine supplements.

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

Toxicity of methionine is rare.

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

If you take methionine supplements without enough folic acid, vitamin B-6, and vitamin B-12, it can cause methionine to change to homocysteine. This may increase your risk for heart disease.

Online Medical Reviewer: Bianca Garilli MD
Online Medical Reviewer: Chris Southard RN
Online Medical Reviewer: Jessica Gotwals RN BSN MPH
Date Last Reviewed: 8/1/2023