* Methionine seems to be safe for treating acetaminophen poisoning, but only under the supervision of a healthcare professional.
*Don’t treat yourself with methionine. It may be UNSAFE to use methionine to self-medicate 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.
* Cancer : Methionine has been shown to play an active part in cancer cell proliferation and malignant tumor growth. Restricting your methionine intake may be the key to stopping cancer in its tracks
*Pregnancy and breast-feeding: Not enough is known about the use of methionine during pregnancy and 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.