Glutathione is a tripeptide (Glu-Cys-Gly, MW ~307.3 g/mol) and the most abundant intracellular antioxidant in mammalian cells. It is critical for Phase II detoxification, free radical scavenging, immune function, and cellular redox homeostasis. Injectable (SC/IV) glutathione bypasses the poor oral bioavailability (~3%) issue and achieves clinically meaningful plasma levels. It has been studied for conditions ranging from non-alcoholic fatty liver disease to Parkinson disease.
Category: Antioxidant / Detoxification. Evidence rating: B (meaningful human data).
Clinical status: Widely used in clinical practice (IV/SC). Multiple Phase II/III trials for NAFLD, Parkinson disease, and cystic fibrosis.
Glutathione functions as the primary intracellular reducing agent, directly scavenging reactive oxygen species (ROS) and serving as a cofactor for glutathione peroxidase and glutathione-S-transferase enzymes. In its reduced form (GSH), it donates electrons to neutralize free radicals and…
Research base: 0 registered clinical trials and 20 indexed publications reference Glutathione.
Safety considerations: Generally well tolerated with injectable administration; Common: mild injection site discomfort, transient flushing with IV push; Rare: nausea, abdominal cramping, bloating.
Reviewed by the PeptideAtlas Editorial Team. Last reviewed: 2026-07-05.
Oral glutathione has extremely poor bioavailability (~3%) due to rapid degradation by GI peptidases and first-pass metabolism. SC injection achieves 100% bioavailability and clinically meaningful plasma levels. Liposomal oral forms are better than standard oral but still inferior to injection.
Yes, clinical evidence supports modest skin lightening through inhibition of tyrosinase and shifting melanin production toward lighter pheomelanin. This effect is dose- and duration-dependent and reversible upon discontinuation.
N-acetyl cysteine (NAC) is a precursor to glutathione — it provides cysteine, the rate-limiting amino acid for glutathione synthesis. NAC is orally bioavailable and raises intracellular glutathione levels over days to weeks. Direct glutathione injection provides immediate elevation but does not enter cells as efficiently as endogenously synthesized glutathione from NAC.
IV glutathione pushes are widely offered in wellness clinics but carry risks including anaphylaxis, Stevens-Johnson syndrome (rare case reports), and kidney toxicity at high doses. The FDA has not approved IV glutathione for any indication. SC injection at lower doses is generally better tolerated.