Glutathione exists in reduced (GSH) and oxidized (GSSG) forms, with the GSH:GSSG ratio serving as a critical indicator of cellular redox status. It is synthesized in all cells from glutamate, cysteine, and glycine — with cysteine availability as the rate-limiting step. Systemic GSH levels decline with age, chronic disease, and oxidative stress, making supplementation of particular interest in longevity and disease contexts.

Oral glutathione has poor bioavailability due to GI degradation — injectable or nebulized forms are preferred for systemic effects. IV glutathione is widely used in clinical practice in Asia and Europe for liver disease, skin brightening (via melanin synthesis inhibition), and chemotherapy adjunct. SubQ delivery has emerged as a more accessible alternative with comparable efficacy for systemic oxidative stress reduction.