Searches for a glutathione dosage usually expect a single number. The published literature does not provide one. The amounts studied differ by route — oral, intravenous and intranasal quantities are not interchangeable — and the most widely circulated "glutathione dosing" information, injectable protocols for cosmetic skin lightening, has essentially no controlled trial data behind it. This article documents what has been investigated, in whom and at what amounts; it is a review of published research, not guidance.
What glutathione is
Glutathione (GSH) is a tripeptide of glutamate, cysteine and glycine. Unlike most compounds in the research-peptide space it is synthesised endogenously and is present in essentially every human cell, functioning as the principal intracellular antioxidant and as a substrate for phase II conjugation reactions. That changes the research question: for most peptides the question is whether the molecule does anything, whereas much of the human glutathione work asks something narrower — whether administering it from outside measurably raises the amount inside cells at all.
The bioavailability problem that frames every oral figure
Any oral quantity has to be read against a 1992 study in the European Journal of Clinical Pharmacology by Witschi and colleagues, which assessed systemic availability in seven healthy volunteers. After a single oral dose of 0.15 mmol per kg of body weight, plasma concentrations of glutathione, cysteine and glutamate did not increase significantly over the following 270 minutes, and the authors concluded that systemic availability of oral glutathione is negligible in humans. The proposed mechanism is hydrolysis by gamma-glutamyl transpeptidase in the intestine and liver, which cleaves the tripeptide back into its constituent amino acids. Reporting of that dose varies: the paper states it in mmol/kg, while secondary summaries commonly restate it as approximately 3 g for an average adult. That single-dose result is why the repeated-administration work below matters, and why an oral figure cannot transfer to another route.
(a) Human clinical trial data
Controlled human research clusters into four areas: oral supplementation and body stores, dermatology, neurology and hepatology. The amounts below are study parameters, not recommendations.
| Study | Population | Amount investigated | Route and duration | Reported focus |
|---|---|---|---|---|
| Richie et al., 2015 (European Journal of Nutrition) | 54 non-smoking adults | 250 mg/day or 1,000 mg/day | Oral, 6 months, randomised, placebo-controlled | Whether supplementation raises glutathione in blood, erythrocytes, plasma and lymphocytes |
| Witschi et al., 1992 | 7 healthy volunteers | 0.15 mmol/kg, single dose | Oral, single administration | Systemic availability, measured over 270 minutes |
| Arjinpathana and Asawanonda, 2012 | 60 healthy adults | 500 mg/day in two divided amounts | Oral, 4 weeks, randomised, double-blind, placebo-controlled | Skin melanin index |
| Weschawalit et al., 2017 | Healthy female participants | GSH 250 mg/day, GSSG 250 mg/day, or placebo | Oral, 12 weeks, randomised, double-blind | Melanin index and skin parameters |
| Hauser et al., 2009 (Movement Disorders) | 21 people with Parkinson's disease (11 active, 10 placebo) | 1,400 mg per infusion | Intravenous, three times weekly, 4 weeks | Safety, tolerability and UPDRS scores |
| Mischley et al., 2017 (Journal of Parkinson's Disease) | 45 people with Hoehn and Yahr stage 1–3 Parkinson's disease | 100 mg or 200 mg, three times daily, versus saline placebo | Intranasal, 3 months, double-blind | UPDRS total and motor subscores |
| Honda et al., 2017 | 34 enrolled with non-alcoholic fatty liver disease; 29 completed | 300 mg/day | Oral, 4 months, open-label single-arm, after 3 months lifestyle intervention | ALT and related markers |
What those studies reported
The Richie trial is the strongest evidence that repeated oral administration raises measured body stores. Glutathione rose by 17% in blood and 29% in erythrocytes in the 250 mg/day group, and by 30–35% in erythrocytes, plasma and lymphocytes in the 1,000 mg/day group at six months. Increases were generally dose- and time-dependent, and returned to baseline after a one-month washout.
The dermatology work — the origin of interest in glutathione for skin — is oral, not injectable. Both the 500 mg/day four-week trial and the 250 mg/day twelve-week trial reported reductions in melanin index. These were small, short studies in healthy volunteers, and reporting of the timepoints at which effects reached significance varies between summaries of the Weschawalit study.
The neurology results are negative. In the intravenous pilot, glutathione was well tolerated with no withdrawals for adverse events, but there were no significant differences in UPDRS change between groups. In the intranasal Phase IIb study, all arms including placebo improved, and the authors concluded the data do not suggest intranasal glutathione is superior to placebo after three months. The NAFLD study reported a significant fall in ALT, but it was open-label and single-arm with no control group and fewer than thirty completers.
(b) Animal and preclinical work
Most mechanistic evidence is in vitro or in animal models: cell-culture work on redox balance, free-radical scavenging and glutathione-S-transferase conjugation, plus animal models of oxidative and hepatic injury. Cell-culture concentrations and animal quantities are not doses and do not convert into human amounts by any reliable rule. Preclinical work is also the source of the proposed melanogenesis mechanism, which is mechanistic support rather than clinical evidence.
(c) Unverified online protocols
The most widely circulated glutathione "dosing" information online concerns injection for cosmetic skin lightening — the part of the field with the weakest evidence base and the clearest regulatory record against it. The Philippine Food and Drug Administration issued Advisory No. 2019-182 on the unsafe use of glutathione as a skin-lightening agent. Its stated position is that no injectable product is approved there for skin lightening; that injectable glutathione is registered in that country only as an adjunct in cisplatin chemotherapy; that no published clinical trials had evaluated injectable glutathione for skin lightening; and that no published guidelines exist for injectable regimens or duration. It lists reported risks including effects on the liver, kidneys and nervous system, and infection risk where injections are given in non-sterile settings.
Vendor pages and forums nonetheless circulate specific injectable amounts and schedules. Those figures are not derived from controlled trials, are not corroborated by any study above, and are not reproduced here.
Regulatory status, stated precisely
Glutathione has a US compounding history that is frequently misdescribed. The FDA's Pharmacy Compounding Advisory Committee voted in June 2022 to recommend adding glutathione to the final 503A Bulks List — trade reporting puts the vote at 8–5 with one abstention — after the FDA's own review had recommended against inclusion, citing insufficient effectiveness and safety data.
Three distinctions matter. A committee recommendation is advisory and non-binding. Inclusion on a 503A compounding bulks list is not drug approval and would not make glutathione an approved medicine. And moving a substance onto the final list requires FDA rulemaking, a separate step from any committee vote. We could not verify the current rulemaking status of glutathione against a primary FDA source at the time of writing; the FDA's own 503A bulk drug substances page is the authority to check, and we are not asserting a status we have not confirmed. The same three distinctions apply to the peptides considered at the July 2026 committee meeting, covered in our explainer on what the July 2026 FDA peptide compounding vote actually means.
What the research does not tell us
- There is no established human dose for glutathione, and no route-independent figure.
- The oral amounts studied (250–1,000 mg/day) sit alongside evidence that single-dose oral availability is negligible; the two are reconciled only by repeated administration over months.
- Intravenous and intranasal quantities were selected for Parkinson's trials and produced results not superior to placebo. They say nothing about any other purpose.
- No published controlled trial supports the injectable cosmetic protocols that dominate online discussion.
- Body-store increases reversed after washout in the one long oral trial.
Key takeaway
Glutathione is unusual in this catalogue in having genuine randomised human data — but that data is mostly oral, mostly short, and negative in the neurological trials. The dermatological signal comes from small oral studies, not from the injectable protocols that circulate most widely. Anyone stating an established glutathione dose is going beyond what has been published.
Research materials
PepSource supplies glutathione as a lyophilised powder in a 1500mg vial, alongside a made-to-order glutathione pen refill cartridge. Every batch is third-party tested for HPLC purity and mass-spectrometry identity, with certificates of analysis published by batch — our guide to reading a certificate of analysis explains what those figures mean. For a comparable review of another tripeptide, see our GHK-Cu dosage review. Material supplied by PepSource is research-grade reagent, not a medicine.
Sources
- Richie JP et al. Randomized controlled trial of oral glutathione supplementation on body stores of glutathione. European Journal of Nutrition, 2015.
- Witschi A et al. The systemic availability of oral glutathione. European Journal of Clinical Pharmacology, 1992.
- Arjinpathana N, Asawanonda P. Glutathione as an oral whitening agent: a randomized, double-blind, placebo-controlled study.
- Weschawalit S et al. Glutathione and its antiaging and antimelanogenic effects. Clinical, Cosmetic and Investigational Dermatology, 2017.
- Hauser RA et al. Randomized, double-blind, pilot evaluation of intravenous glutathione in Parkinson's disease. Movement Disorders, 2009.
- Mischley LK et al. Phase IIb study of intranasal glutathione in Parkinson's disease. Journal of Parkinson's Disease, 2017.
- Honda Y et al. Efficacy of glutathione for the treatment of nonalcoholic fatty liver disease: an open-label, single-arm, multicenter, pilot study. 2017.
- Philippine FDA Advisory No. 2019-182: Unsafe use of glutathione as a skin-lightening agent.
- US FDA. Bulk drug substances used in compounding under section 503A of the FD&C Act.
- Alliance for Pharmacy Compounding. PCAC recommends glutathione for bulks list, June 2022.
Research use only. All products referenced are supplied strictly as research reagents for laboratory and in-vitro use, and are not for human or veterinary consumption.