Oxidized glutathione (GSSG) is the disulfide form of glutathione, a tripeptide crucial for cellular redox balance. Unlike reduced glutathione (GSH), which acts as a direct antioxidant, GSSG is generated during the neutralization of reactive oxygen species and serves as an indicator of oxidative stress. It is widely used in biochemical research to study redox signaling, glutathione peroxidase and reductase activities, and the overall antioxidant defense system. In medical and pharmacological applications, GSSG is employed in assays for measuring oxidative stress levels in conditions like cancer, diabetes, neurodegenerative diseases, and cardiovascular disorders. It also finds use in developing therapies that modulate the GSH/GSSG ratio to restore cellular homeostasis. In biotechnology, GSSG is utilized as a standard in enzymatic assays and for protein folding studies involving disulfide bonds. While not typically used in cosmetics or food preservation like GSH, it supports research into aging and inflammation-related mechanisms.