The cell's master antioxidant
Oral, Injection, Topical · 503A Compounding
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.
Researched and maintained by the PepHookup team. Regulatory status last verified April 12, 2026.
T-cell proliferation, cytotoxic CD8+ activity, and natural killer cell function are sensitive to intracellular glutathione. In a 6-month randomized trial, high-dose oral GSH more than doubled NK cell cytotoxicity, and a liposomal pilot raised it by up to 400% within two weeks.[4][5][3]
Glutathione (GSH, gamma-L-glutamyl-L-cysteinyl-glycine) is a tripeptide of glutamate, cysteine, and glycine with a molecular weight of 307 daltons. It is the most abundant non-protein thiol in human cells, sitting at intracellular concentrations of about 1 to 10 mM. The bond between glutamate and cysteine is an unusual gamma linkage formed through the side-chain carboxyl group rather than the standard alpha-carboxyl, which shields the molecule from cleavage by most peptidases and gives it its characteristic stability.
The liver holds the highest concentrations and is the main site of synthesis and export. Inside cells, roughly 80 to 85% of glutathione is cytosolic, with about 10 to 15% in mitochondria and the rest in the endoplasmic reticulum and nucleus. Synthesis runs in two ATP-dependent steps. Glutamate-cysteine ligase joins glutamate to cysteine in the rate-limiting reaction, which is constrained by cysteine availability, and glutathione synthetase then adds glycine to finish the tripeptide.
Because the body makes its own glutathione continuously, it is not a classic drug but an endogenous molecule that can be supplemented. Synthesis capacity declines with age. Stable-isotope studies in older adults found markedly lower red-cell glutathione driven by a reduced synthesis rate, which supplementing the precursors cysteine and glycine corrected within two weeks.
The cysteine thiol is the reactive heart of the molecule. It donates a hydrogen atom to quench reactive oxygen species and free radicals, and in the process two GSH molecules are oxidized and joined by a disulfide bond to form glutathione disulfide (GSSG). Glutathione reductase then regenerates GSH from GSSG using NADPH, sustaining the high GSH-to-GSSG ratio that marks a healthy redox environment. Glutathione peroxidases, a family of selenium-dependent enzymes, use GSH to reduce hydrogen peroxide and lipid hydroperoxides.
In Phase II metabolism, glutathione S-transferases catalyze conjugation of GSH to electrophilic compounds far faster than the same reactions would occur spontaneously, tagging xenobiotics and endogenous toxins for excretion. The glyoxalase system separately uses GSH to clear methylglyoxal, a damaging byproduct of glucose metabolism.
Immune function is closely tied to glutathione status. Work summarized by Droge and Breitkreutz showed that lymphoid cells require a balanced intracellular glutathione level, and that even moderate shifts affect T-cell proliferation, CD8+ activity, interleukin-2-dependent responses, and NK cell activity. In glutathione-depleted states such as advanced HIV infection, immune function suffers, and precursor repletion has been shown to restore measures of cytotoxic activity.
Glutathione is also depleted early in Parkinson's disease, where the substantia nigra shows reduced GSH content. That observation motivated trials of intravenous and intranasal glutathione, although the controlled evidence for symptom relief in Parkinson's remains weak.
The cell's master antioxidant
Glutathione maintains cellular redox balance through GSH/GSSG cycling, neutralizes reactive oxygen species directly and through glutathione peroxidases, detoxifies xenobiotics via glutathione S-transferase conjugation, protects the mitochondrial pool, and supports immune cell function. Its gamma peptide bond and 1 to 10 mM intracellular concentration make it the dominant non-protein thiol in human cells.
Oral GSH at 250 or 1,000 mg/day raised glutathione 30 to 35% in erythrocytes, plasma, and lymphocytes and 260% in buccal cells at the high dose, with NK cell cytotoxicity more than doubling versus placebo. Levels returned to baseline after washout. This was the first controlled human evidence that oral glutathione meaningfully raises body stores.
Richie JP Jr, Nichenametla S, Neidig W, et al. · Eur J Nutr, 54(2):251-263 (2015) · PubMed
Within two weeks, whole-blood GSH rose about 40% and peripheral blood mononuclear cell GSH up to 100%, with plasma 8-isoprostane down 35%. NK cell cytotoxicity increased by up to 400% and lymphocyte proliferation by up to 60%. The authors note the small sample limited statistical power and no dose-response was seen.
Sinha R, Sinha I, Calcagnotto A, et al. · Eur J Clin Nutr, 72(1):105-111 (2018) · PubMed
A sublingual GSH form raised plasma total and reduced glutathione and the GSH/GSSG ratio more than standard oral GSH (p = 0.003) and was the only arm to significantly raise plasma vitamin E (p = 0.04). The authors concluded the sublingual form was superior to both oral GSH and NAC for supplementation.
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 and improved markers of liver fat. As an uncontrolled pilot it cannot separate the drug effect from the preceding lifestyle changes, but it was the first clinical signal for oral glutathione in fatty liver disease.
Honda Y, Kessoku T, Sumida Y, et al. · BMC Gastroenterol, 17(1):96 (2017) · PubMed
Intranasal GSH at 100 or 200 mg three times daily for 3 months improved UPDRS scores from baseline, but neither dose was superior to placebo, which itself improved more than expected. One high-dose participant developed cardiomyopathy. The trial argued for a delayed-start design rather than confirming benefit.
Mischley LK, Lau RC, Shankland EG, Wilbur TK, Padowski JM · J Parkinsons Dis, 7(2):289-299 (2017) · PubMed
Supplying the glutathione precursors glycine and N-acetylcysteine for 16 weeks corrected glutathione deficiency and improved oxidative stress, mitochondrial function, inflammation, insulin resistance, and physical function. This indirect strategy is among the better-controlled human evidence for restoring glutathione.
Kumar P, Liu C, Suliburk J, et al. · J Gerontol A Biol Sci Med Sci, 78(1):75-89 (2023) · PubMed
start low, go slow
Intravenous
Oral (standard reduced)
Oral (liposomal)
Sublingual
Intravenous: Administered only by licensed clinicians, often alongside vitamin C and B vitamins. The Hauser Parkinson's trial used 1,400 mg three times weekly with a placebo-comparable safety profile.
Oral (standard reduced): Bioavailability was long considered poor, but the Richie 2015 RCT showed dose-dependent increases in body glutathione stores over 6 months.
Oral (liposomal): Lipid encapsulation is intended to improve absorption. A small pilot raised blood and immune-cell glutathione within two weeks.
Sublingual: The Schmitt crossover trial found a sublingual form raised the GSH/GSSG ratio more than both standard oral GSH and NAC.
Dosing, route, and duration are determined by a licensed provider based on the indication, the degree of glutathione depletion, and tolerance. The figures here reflect protocols reported in the research literature, not a prescription.
Delivery form matters more for glutathione than for most peptides. Liposomal and sublingual products are designed to overcome the limited absorption of standard reduced glutathione, and the one head-to-head trial favored a sublingual form over both oral GSH and NAC.
Benefits are most evident in people with documented depletion from aging, chronic disease, or metabolic syndrome. In healthy people with normal glutathione, raising stores above baseline is less likely to produce a noticeable functional change.
Because cysteine is the rate-limiting precursor, some providers favor supplying NAC and glycine to drive endogenous synthesis rather than dosing glutathione directly. The GlyNAC trial is the strongest controlled evidence for that approach.
Glutathione is an endogenous molecule found in every cell. Oral trials up to 1,000 mg/day for 6 months reported no serious adverse events, and the intravenous Parkinson's trial at 1,400 mg three times weekly had a safety profile comparable to placebo.
The inhaled and nebulized routes carry a real risk of bronchospasm, especially in people with asthma or reactive airway disease, so pretreatment with a bronchodilator is often recommended when this route is used.
One participant in the intranasal Parkinson's trial developed cardiomyopathy. The event was not clearly attributed to glutathione, but it underscores why these therapies belong under medical supervision.
A theoretical concern exists about high-dose antioxidant supplementation during active chemotherapy or radiation, since glutathione could in principle shield tumor cells from oxidant-dependent killing. This remains debated in the oncology literature and is a question for the treating oncologist.
| Peptide | Primary Use | Administration | Cycle Length | Key Differentiator |
|---|---|---|---|---|
| Glutathione | Antioxidant & Detoxification | IV, Oral, Sublingual, Topical | Ongoing supplementation | The body's own master antioxidant, with controlled human data showing oral and sublingual forms can raise body stores and immune markers |
| SS-31 (Elamipretide) | Mitochondrial restoration and rare mitochondrial disease | Subcutaneous injection (daily); IV in trials | Ongoing daily dosing | The first FDA-approved mitochondria-targeted therapeutic; binds cardiolipin on the inner mitochondrial membrane to support electron transport efficiency |
| GHK-Cu | Anti-Aging & Skin Regeneration | Topical, Injection | 8-12 weeks | A naturally occurring copper-carrier peptide that rebuilds the skin matrix and, per gene-expression analysis, shifts expression of about a third of human genes toward repair |
| Sermorelin | GH restoration and healthy aging | Subcutaneous injection, daily at bedtime | 3-6 months | The GHRH analog with prior FDA approval and a multi-decade clinical record, preserving natural feedback rather than replacing growth hormone |
| Thymosin Alpha-1 | Immune Support | Injection | 6-12 months (chronic) / short courses (acute) | Bidirectional immunomodulation that can strengthen suppressed immunity while helping temper hyperinflammation; approved as a pharmaceutical in 35+ countries |
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.
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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