L-Glutathione
Also known as: GSH, Reduced Glutathione, L-GSH, Reduced L-Glutathione, γ-glutamylcysteinylglycine
Effective Dosage
250–65 mg/kg/day depending on indication; No single universal dose established
What the Science Says
L-Glutathione is a small protein made of three amino acids that your body produces naturally and uses as its primary internal antioxidant. As a supplement, it has shown the most consistent results in two specific areas: improving skin tone and reducing dark spots when combined with L-Cystine (500 mg L-Cystine + 250 mg L-Glutathione daily for 12 weeks in Asian women), and supporting weight and growth in children with cystic fibrosis (at 65 mg/kg/day for 6 months). A sublingual formulation showed modest improvements in cholesterol levels in people with cardiovascular risk factors, though it did not significantly improve blood vessel function in the overall study group.
What It Doesn't Do
Won't detox your liver on its own — the NAFLD study used it as part of a multi-ingredient formula plus a diet, so you can't credit glutathione alone. Not proven to boost your immune system in healthy adults. No evidence it reverses aging or 'cleanses' your body. Oral pills may not raise blood glutathione levels meaningfully — absorption is a real problem. Don't expect dramatic antioxidant effects from a standard capsule dose.
Evidence-Based Benefits
Oral L-Cystine combined with L-Glutathione (500 mg + 250 mg daily) showed significant skin lightening and reduction in facial dark spots in Asian women over 12 weeks compared to placebo (PMID: 33834608). Oral reduced GSH at 65 mg/kg/day significantly improved weight, BMI, height, and gut inflammation markers in pediatric cystic fibrosis patients over 6 months (PMID: 25633497). Sublingual L-GSH supplementation was associated with reductions in total and LDL cholesterol and improved arterial stiffness in a small subset of cardiovascular risk patients with baseline endothelial dysfunction (PMID: 28526381).
Weak EvidenceEffective at: 250 mg/day (skin lightening, combined with L-Cystine); 65 mg/kg/day (pediatric CF); sublingual formulations studied for cardiovascular effects — No single universal established dose
Source: auto-research
Absorption & Bioavailability
Poor to Moderate — oral glutathione is partially broken down in the gut before absorption. Sublingual delivery may improve uptake by bypassing digestion. One study specifically tested a sublingual formulation to address this limitation. Combination with L-Cystine may enhance effectiveness by providing precursor amino acids.
Red Flags to Watch For
- Most oral glutathione supplements may not raise blood glutathione levels effectively due to poor gut absorption — delivery method matters greatly
- The NAFLD/liver study used a multi-ingredient formula (also containing Vitamin E, silymarin, and other compounds), making it impossible to attribute benefits to glutathione alone
- Skin-lightening claims are real but were studied only in Asian women using a specific L-Cystine + L-Glutathione combination — results may not generalize to all populations or standalone glutathione products
- Many products in the NIH DSLD (1,000+ registered) make broad health claims not supported by the clinical evidence available
- Doses used in studies vary widely by condition — there is no one-size-fits-all dose, and most product labels don't match studied doses
Products Containing L-Glutathione
See how L-Glutathione is used in these analyzed products:
Research Sources
- PubMed
- NIH DSLD
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-04-06