Other Name(s):

DL-Methionine, DL-Méthionine, L-2-amino-4-(methylthio)butyric acid, L-Methionine, L-Méthionine, Méthionine, Metionina.


Methionine is an amino acid. Amino acids are the building blocks that our bodies use to make proteins. Methionine is found in meat, fish, and dairy products, and it plays an important role in many cell functions.

Methionine is used to prevent liver damage in acetaminophen (Tylenol) poisoning. It is also used for increasing the acidity of urine, treating liver disorders, and improving wound healing. Other uses include treating depression, alcoholism, allergies, asthma, copper poisoning, radiation side effects, schizophrenia, drug withdrawal, and Parkinson's disease.

How does it work?

In acetaminophen poisoning, methionine prevents the breakdown products of acetaminophen from damaging the liver.


Long-term heavy alcohol consumption can cause: See Answer

Uses & Effectiveness

Possibly Effective for...

  • Acetaminophen (Tylenol) poisoning. Research shows that receiving methionine by mouth or intravenously (by IV) seems to be effective for treating acetaminophen poisoning. Treatment should begin as quickly as possible, but must start within 10 hours of acetaminophen overdose.

Insufficient Evidence to Rate Effectiveness for...

  • Cobalamin deficiency. Long-term exposure to nitrous oxide, which is given for anesthesia during surgery, might cause side effects that resemble cobalamin deficiency. Some research suggests that taking methionine by mouth before surgery might reduce these side effects of nitrous oxide.
  • Colon cancer. Eating a diet that rich in methionine and folate (a type of B vitamin) seems to help reduce the risk of colon cancer. This seems to be especially true for people with a family history of colon cancer and people who drink large amounts of alcohol.
  • Neural tube birth defects. Women who consume more dietary methionine during pregnancy seem to have a lower risk of neural tube birth defects.
  • Parkinson's disease. Early research suggests that taking L-methionine by mouth for up to 6 months improves symptoms of Parkinson's disease, such as tremor, inability to control movements, and rigidity.
  • Liver function.
  • Depression.
  • Alcoholism.
  • Allergies.
  • Asthma.
  • Radiation side effects.
  • Schizophrenia.
  • Drug withdrawal.
  • Other conditions.
More evidence is needed to rate the effectiveness of methionine for these uses.

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).

Side Effects

Methionine is POSSIBLY SAFE when taken by mouth or injected intravenously (by IV) to treat acetaminophen poisoning, but only under the supervision of a healthcare professional.

Don't treat yourself with methionine. It is POSSIBLY UNSAFE to self-medicate with methionine if you use larger amounts than those typically found in food. Too much methionine can cause brain damage and death. Methionine can increase blood levels of homocysteine, a chemical that might cause heart disease. Methionine might also promote the growth of some tumors.

Special Precautions & Warnings:

Children: Methionine is POSSIBLY SAFE for children when given by mouth or injected intravenously (by IV) to treat acetaminophen poisoning, but only under the supervision of a healthcare professional. Methionine is POSSIBLY UNSAFE when injected intravenously into infants that are receiving parenteral nutrition.

Pregnancy and breast-feeding: There is not enough reliable information about the safety of taking methionine if you are pregnant or breast-feeding. Stay on the safe side and avoid use.

Acidosis: Methionine can cause changes in acidity of the blood and should not be used in people with a condition called acidosis.

“Hardening of the arteries” (atherosclerosis): There is some concern that methionine might make atherosclerosis worse. Methionine can increase blood levels of a chemical called homocysteine, especially in people who don't have enough folate, vitamin B12, or vitamin B6 in their bodies, or in people whose bodies have trouble processing homocysteine. Too much homocysteine is linked to an increased risk for diseases of the heart and blood vessels.

Liver disease, including cirrhosis: Methionine might make liver disease worse.

Methylenetetrahydrofolate reductase (MTHFR) deficiency: This is an inherited disorder. It changes the way the body processes homocysteine. People who have this disorder should not take methionine supplements because methionine might cause homocysteine to build up in these people. Too much homocysteine might increase the chance of developing diseases of the heart or blood vessels.

Schizophrenia: Large doses of methionine (e.g., 20 g/day for 5 days) might cause confusion, disorientation, delirium, agitation, listlessness, and other similar symptoms in people with schizophrenia.


Hepatitis C, Hep B, Hep A: Symptoms, Causes, Treatment See Slideshow


The following doses have been studied in scientific research:


  • For acetaminophen (Tylenol) poisoning: 2.5 grams of methionine every 4 hours for 4 doses to prevent liver damage and death. Methionine must be given within 10 hours of taking the acetaminophen. This should be done by a healthcare professional.

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