A molecule the body makes; levels fall with age. Sustained oral dosing raises stored amounts, but blood levels have never predicted a health outcome. Skin lightening is the best-supported effect and reverses once dosing stops. Oral use was well tolerated over six months. Serious harms cluster in the unregulated injectable market. The cheaper building block has never been compared. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Whole-blood reduced glutathione (GSH) | 900–1,400 µmol/L | Confirms the supplement is reaching the blood compartment |
| Reduced-to-oxidized glutathione ratio (GSH:GSSG) | Above 10:1 | Reflects redox balance better than total glutathione |
| Gamma-glutamyl transferase | Below 20 U/L in men, below 15 U/L in women | Rises when glutathione turnover and oxidative burden are high |
| Alanine aminotransferase (ALT) | Below 25 U/L in men, below 20 U/L in women | The endpoint that moved in the fatty liver trial |
| HbA1c | 5.0–5.4% | The one validated clinical surrogate that shifted in a randomized glutathione trial |
| High-sensitivity C-reactive protein | Below 1.0 mg/L | General inflammation marker that fell alongside oxidative measures in the precursor trial |
| Urinary 8-OHdG | No established target; track change from the individual's own baseline | Marker of oxidative damage to DNA, the largest effect seen in the diabetes trial |
Cadence: Baseline panel before starting; the redox pair repeated at 4–8 weeks to confirm exposure; liver enzymes, HbA1c and inflammation reassessed at 3 months and again at 6 months; then every 6–12 months on continued use.