The best times to take glutamine are right before bed, immediately upon waking, and 30 minutes before or after exercising, according to Bodybuilding.com. Glutamine works best at these times to improve lean muscle mass and strength.
Glutamine should not be taken at the same time as creatine, another muscle building supplement, as they compete with one another for absorption by the body, reports Bodybuilding.com. For best results, limit glutamine intake to right before bed and immediately upon waking up to raise growth hormone levels significantly, and use creatine before and after a workout.
Diabetics metabolize glutamine abnormally, and they should consult a doctor before using the supplement, says Muscle and Strength.