You shouldn't worry about Glutamine side effects, as studies have found it to have no adverse side effects, and also because Glutamine naturally occurs in your body, it has no health risks. However, like all supplements, too much is never a good idea. Taking excessive amounts of L-Glutamine has led to upset stomachs, so you should follow the recommended dosages. Most bodybuilders take between 10 and 15 grams a day or so spaced out evenly.