Glutamic acid is generally free of side effects for the vast majority of people who take it; however, people with kidney or liver disease should not consume high intakes of amino acids without consulting a healthcare professional. Because over stimulation of glutamate receptors is thought to be a possible cause of certain neurological diseases (e.g., amyotrophic lateral sclerosis [Lou Gehrig’s disease] and epilepsy), people with a neurological disease should consult of physician before supplementing with glutamate.

Monosodium glutamate (MSG), the form of glutamic acid that is used as a flavour enhancer, has been reported in anecdotal studies to have a number of different adverse effects (including headache, fatigue, and depression). However, controlled trials have failed to confirm that MSG causes these side effects, and the safety of this compound remains controversial.