The cell's master antioxidant
A tripeptide antioxidant central to cellular redox, detoxification, and immune function.
Educational content. This page describes Glutathione for informational purposes only and is not medical advice, diagnosis, or treatment. Consult a licensed provider before starting, stopping, or modifying any therapy.
Maintains the primary intracellular redox buffer at 1 to 10 mM concentrations, with the GSH/GSSG cycling system neutralizing reactive oxygen species and keeping over 90% of cellular glutathione in its protective reduced form.[7]
Conjugates electrophilic xenobiotics, carcinogens, and toxic metabolites through glutathione S-transferase enzymes at rates approximately 100 times faster than nonenzymatic reactions, making them water-soluble for excretion.[7]
Glutathione (GSH, gamma-L-glutamyl-L-cysteinyl-glycine) is a tripeptide composed of glutamate, cysteine, and glycine, with a molecular weight of 307 daltons. It is the most abundant non-protein thiol in mammalian cells, present at intracellular concentrations of 1 to 10 mM. The bond between glutamate and cysteine is an unusual gamma peptide bond formed through the gamma-carboxyl group rather than the standard alpha-carboxyl, which protects the molecule from cleavage by most intracellular peptidases.
The liver contains the highest concentrations and is the primary organ for glutathione synthesis and export. Within cells, the cytosol holds 80 to 85% of total glutathione, with 10 to 15% in mitochondria and the remainder in the endoplasmic reticulum. Synthesis occurs in two ATP-dependent steps: glutamate-cysteine ligase joins glutamate to cysteine (the rate-limiting step, dependent on cysteine availability), and glutathione synthetase adds glycine to complete the tripeptide.
Glutathione's cysteine thiol group donates a hydrogen atom to neutralize reactive oxygen species and free radicals. Two GSH molecules are oxidized and joined by a disulfide bond to form GSSG (glutathione disulfide). Glutathione reductase then regenerates GSH from GSSG using NADPH as the electron donor, maintaining the high GSH:GSSG ratio (typically above 90:10) that indicates healthy redox status. Glutathione peroxidases, a family of selenium-containing enzymes, catalyze the reduction of hydrogen peroxide and lipid hydroperoxides using GSH.
In Phase II detoxification, glutathione S-transferase enzymes catalyze conjugation of GSH to electrophilic toxins, drugs, and endogenous metabolites like 4-hydroxynonenal, making them water-soluble for excretion via bile or urine. The glyoxalase system also uses GSH to detoxify methylglyoxal, a harmful metabolic byproduct.
Immune function is tightly coupled to glutathione levels. According to research by Droge and Breitkreutz, the immune system requires a delicately balanced intermediate level of glutathione in lymphoid cells. Even moderate changes profoundly affect T-cell proliferation, CD8+ activity, interleukin-2-dependent functions, and natural killer cell activity. In HIV-infected patients, massive cysteine and GSH losses were associated with severe immunosuppression, and NAC supplementation nearly completely restored NK cell activity in randomized trials.
The cell's master antioxidant
Glutathione maintains cellular redox homeostasis through the GSH/GSSG cycling system, detoxifies xenobiotics and endogenous toxins via glutathione S-transferase conjugation, protects mitochondrial integrity, and supports immune cell function including T-cell proliferation and natural killer cell cytotoxicity. Its gamma peptide bond and intracellular concentrations of 1 to 10 mM make it the dominant non-protein thiol in human cells.
Key studies supporting the therapeutic use of this peptide.
Oral GSH at 250 or 1,000 mg/day increased glutathione levels 30 to 35% in erythrocytes, plasma, and lymphocytes, with 260% increase in buccal cells at the high dose. NK cell cytotoxicity increased over 2-fold at the high dose. This landmark study challenged earlier assumptions that oral glutathione lacked bioavailability.
Richie JP Jr, Nichenametla S, Neiber W, et al. — Eur J Nutr, 54(2):251-263 (2015) · PubMed
Elevated whole blood GSH by 40% and peripheral blood mononuclear cell GSH up to 100% within 2 weeks. Oxidative stress marker 8-isoprostane decreased 35%. NK cell cytotoxicity increased 400% and lymphocyte proliferation increased 60%.
Sinha R, Sinha I, Calcagnotto A, et al. — Eur J Clin Nutr, 72(1):105-111 (2018) · PubMed
Sublingual GSH was superior to both oral GSH and NAC. The sublingual form increased the GSH/GSSG ratio significantly versus oral GSH (p = 0.003) and increased plasma vitamin E (p = 0.04). Sublingual showed 65% GSH/GSSG ratio improvement over NAC and 230% over standard oral GSH.
Schmitt B, Vicenzi M, Garrel C, Denis FM — Redox Biol, 6:198-205 (2015) · PubMed
Oral GSH at 300 mg/day for 4 months significantly reduced ALT levels, hepatic steatosis, and markers of liver fibrosis. First clinical study of oral glutathione in NAFLD.
Honda Y, Kessoku T, Sumida Y, et al. — BMC Gastroenterol, 17(1):96 (2017) · PubMed
Typical protocols used in clinical practice. Always consult a licensed provider for personalized dosing.
Intravenous
Oral (standard reduced)
Oral (liposomal)
Sublingual
Intravenous: Must be administered by licensed healthcare professionals. Often combined with B vitamins and vitamin C.
Oral (standard reduced): Bioavailability was historically considered poor, but the Richie et al. 2015 RCT demonstrated meaningful increases in body glutathione stores.
Oral (liposomal): Improved absorption; demonstrated effectiveness for raising blood and immune cell glutathione levels in the Sinha et al. study.
Sublingual: The Schmitt et al. crossover trial showed superior bioavailability compared to both standard oral glutathione and NAC.
Liposomal and sublingual forms demonstrate substantially better absorption than standard reduced glutathione capsules. The Schmitt et al. crossover trial directly showed sublingual GSH outperforming both oral GSH and NAC for improving the GSH/GSSG ratio.
IV glutathione provides the highest and most immediate tissue levels but requires clinical administration. Common research protocols use 600 to 1,400 mg administered 1 to 3 times per week.
Benefits of supplementation are most pronounced in individuals with documented glutathione depletion from aging, chronic disease, or metabolic syndrome. In healthy individuals with normal GSH levels, supplementation is less likely to enhance function above baseline.
Glutathione is an endogenous molecule present in every cell. Clinical trials of oral supplementation up to 1,000 mg/day for 6 months reported no serious adverse events and high compliance rates. The IV route at doses up to 1,400 mg showed adverse events comparable to placebo in the Hauser Parkinson's trial.
Nebulized glutathione carries a real risk of bronchospasm, particularly in patients with asthma or reactive airway disease. The largest CF trial (153 patients) showed acceptable tolerability but documented airway reactivity concerns. Pre-bronchodilator treatment is recommended.
A theoretical concern exists regarding high-dose antioxidant supplementation during active chemotherapy or radiation therapy, as glutathione could potentially protect tumor cells from ROS-dependent killing mechanisms. This remains debated in the oncology literature.
See how Glutathione compares to peptides with overlapping benefits.
| Peptide | Primary Use | Administration | Cycle Length | Key Differentiator |
|---|---|---|---|---|
| Glutathione | Antioxidant & Detoxification | IV, Oral, Sublingual | Ongoing supplementation | The body's own master antioxidant, with clinical data supporting oral bioavailability (challenging earlier assumptions) and dramatic immune cell activation at high doses |
| SS-31 (Elamipretide) | Mitochondrial Restoration & Anti-Aging | Injection (daily) | Continuous (weeks to months) | Only peptide that directly targets cardiolipin on the inner mitochondrial membrane to restore electron transport chain efficiency |
| GHK-Cu | Anti-Aging & Recovery | Topical, Injection | 8–12 weeks | Only peptide demonstrated to modulate ~31% of human genes, epigenetically resetting cellular function toward a younger phenotype |
| Sermorelin | Anti-Aging & GH Restoration | Injection (daily) | 3–6 months | Only GHRH analog with FDA approval history and multi-decade safety record, uniquely preserving natural GH feedback |
| Thymosin Alpha-1 | Immune Support | Injection | 6–12 months (chronic) / 1–4 weeks (acute) | Only peptide with bidirectional immunomodulation, enhancing suppressed immunity while regulating hyperinflammation, approved in 35+ countries |
Current FDA classification and compounding eligibility.
This substance is in Category 1 of the FDA's 503A bulk drug substances evaluation. Licensed 503A pharmacies may compound it under FDA enforcement discretion while the agency continues its review.
On the 503A Category 1 list and compoundable under the interim policy. The FDA recommended against inclusion on the permanent bulks list due to insufficient safety data, but the PCAC voted to include it. FDA's final decision is still pending. Widely used in IV and injection compounding for antioxidant therapy.
FDA final rulemaking decision on 503A bulks list inclusion (PCAC voted to include). Expected 2026–2027.
Listed on 503A Category 1 as compoundable under interim enforcement policy
FDA PCAC reviewed glutathione; FDA recommended against inclusion, but PCAC voted to include on bulks list
Last verified April 12, 2026. PepHookup tracks public FDA actions. This is not legal or medical advice.
Sechi G, Deledda MG, Bua G, et al. “Reduced intravenous glutathione in the treatment of early Parkinson's disease.” Prog Neuropsychopharmacol Biol Psychiatry, 20(7):1159-1170 (1996)
Hauser RA, Lyons KE, McClain T, et al. “Randomized, double-blind, pilot evaluation of intravenous glutathione in Parkinson's disease.” Mov Disord, 24(7):979-983 (2009)
Richie JP Jr, Nichenametla S, Neiber W, et al. “Randomized controlled trial of oral glutathione supplementation on body stores of glutathione.” Eur J Nutr, 54(2):251-263 (2015)
Sinha R, Sinha I, Calcagnotto A, et al. “Oral supplementation with liposomal glutathione elevates body stores of glutathione and markers of immune function.” Eur J Clin Nutr, 72(1):105-111 (2018)
Schmitt B, Vicenzi M, Garrel C, Denis FM “Effects of N-acetylcysteine, oral glutathione (GSH) and a novel sublingual form of GSH on oxidative stress markers: A comparative crossover study.” Redox Biol, 6:198-205 (2015)
Honda Y, Kessoku T, Sumida Y, et al. “Efficacy of glutathione for the treatment of nonalcoholic fatty liver disease: an open-label, single-arm, multicenter, pilot study.” BMC Gastroenterol, 17(1):96 (2017)
Droge W, Breitkreutz R “Glutathione and immune function.” Proc Nutr Soc, 59(4):595-600 (2000)
Griese M, Kappler M, Eismann C, et al. “Inhalation treatment with glutathione in patients with cystic fibrosis.” Am J Respir Crit Care Med, 188(1):83-89 (2013)
Mischley LK, Conley KE, Shankland EG, et al. “Central nervous system uptake of intranasal glutathione in Parkinson's disease.” NPJ Parkinsons Dis, 3:18 (2017)
Kumar P, Liu C, Suliburk J, et al. “Supplementing Glycine and N-Acetylcysteine (GlyNAC) in Older Adults Improves Glutathione Deficiency, Oxidative Stress, Mitochondrial Dysfunction, Inflammation, Physical Function, and Aging Hallmarks: A Randomized Clinical Trial.” J Gerontol A Biol Sci Med Sci, 78(1):75-89 (2023)
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