||Glutamine (Gln) is one of the most abundant amino acids containing an uncharged amide as a side chain. It is synthesized via condensation of glutamate and ammonia. Gln is classified as a non-essential amino acid, however, Gln is important in several biological processes such as protein synthesis, regulation of acid-balance in mammalian kidneys and cell growth. It constitutes cell’s main source of nitrogen for the synthesis of nucleotides and hexosamines. Glutamine-rich diets benefit patients suffering from Crohn’s disease, severe burns, HIV/AIDS and cancer. Glutamine Colorimetric Assay kit is a simple and sensitive assay that detects the biologically relevant concentrations of Gln in various fluids and tissues. The assay is based on the hydrolysis of Glutamine to Glutamate producing a stable signal, which is directly proportional to the amount of Gln in the sample. The assay can detect as little as 25 μM of Gln in a variety of biological samples.