L-glutamine (L-GLN) is considered a nonessential amino acid that has a variety of applications in naturopathic medicine. It has been postulated that in the critically ill patient, GLN becomes an essential amino acid for recovery, restoration, and repair at a cellular level. Mucositis is an intestinal mucosal damage of the gastrointestinal tract--mouth, throat, stomach, intestines, rectum, and anus--that is caused directly by chemotherapies and radiotherapies. Cancer cachexia is a significant biochemical event, which is characterized by weight loss, fatigue, and indicative of depletion of skeletal muscle GLN--a hypercatabolic state. There has been some question as to the use of GLN in this patient population because of its role as a preferred energy source not only for enterocytes and lymphocytes but for malignant cells as well.This article will address the questions of safety, efficacy, dosing, and toxicity of GLN used as an integrative therapeutic in ongoing integrative cancer treatment.