Unusually, the glutathione dosage question has plenty of published answers. They disagree with each other, and the disagreements are the useful part.
The short version
Oral trials used 250 mg and 1,000 mg a day for six months, and 500 mg twice a day for four weeks. One found body stores rose. One found nothing changed. The intravenous work used 600 mg twice daily and 1,400 mg three times a week.
Glutathione is a tripeptide the body already makes in every cell, at millimolar concentrations. That is what makes the dosing question strange: this is not a compound being introduced, it is one being topped up, and the literature is really about whether topping it up is even possible.
What the glutathione trials administered
| Study | Species | Dose | Route | Duration | n |
|---|---|---|---|---|---|
| Witschi et al., 1992 | Human (healthy volunteers) | 0.15 mmol/kg, about 3 g, single dose | Oral | Single dose | 7 |
| Richie et al., 2015 | Human (non-smoking adults) | 250 or 1,000 mg per day | Oral | 6 months | 54 |
| Allen & Bradley, 2011 | Human (healthy adults) | 500 mg twice daily | Oral | 4 weeks | 40 enrolled, 39 completed |
| Wahab et al., 2021 | Human (skin pigmentation) | — | Oral plus topical | 8 weeks | 46 |
| Sechi et al., 1996 | Human (early Parkinson's disease) | 600 mg twice daily | Intravenous | 30 days, open label | 9 |
| Hauser et al., 2009 | Human (Parkinson's disease) | 1,400 mg three times a week | Intravenous | 4 weeks | 21 (11 vs 10) |
A dash means we have no sourced figure for that cell and have not estimated one.
Six human trials, four routes-and-endpoint combinations, and no two of them asking the same question. That is why the charts for this compound are so inconsistent.
The oral literature argues with itself
Witschi and colleagues gave seven volunteers a single 3 g oral dose and measured plasma glutathione, cysteine and glutamate for 270 minutes. Nothing rose significantly. Their conclusion was that systemic availability of oral glutathione is negligible.
Richie and colleagues took a different approach: 250 mg or 1,000 mg daily for six months in 54 adults, measuring body stores rather than acute plasma. At the high dose, glutathione rose 30 to 35% in red cells, plasma and lymphocytes, and 260% in cheek-lining cells.
It is not possible to increase circulating glutathione to a clinically beneficial extent by the oral administration of a single dose of 3 g of glutathione.
Witschi et al., European Journal of Clinical Pharmacology, 1992Allen and Bradley gave 500 mg twice daily for four weeks to 40 adults and found no significant change in oxidative stress markers or in glutathione status.
No significant changes were observed in biomarkers of oxidative stress, including glutathione status, in this clinical trial of oral glutathione supplementation in healthy adults.
Allen & Bradley, Journal of Alternative and Complementary Medicine, 2011- Acute plasma — unchanged by a single 3 g dose.
- Body stores over six months — up 30 to 35% at 1,000 mg a day.
- Oxidative stress markers over four weeks — unchanged at 500 mg twice daily.
- A single large dose does not raise plasma acutely. That is settled.
- Months of daily dosing raised measured body stores in the largest and longest study.
- Weeks of daily dosing did not move oxidative stress markers, which is a different endpoint again.
Glutathione
The reduced tripeptide studied across the literature reviewed here. Research use only — supplied with a batch-matched certificate of analysis.
The intravenous literature is smaller and went backwards
Sechi and colleagues gave nine patients with early, untreated Parkinson's disease 600 mg intravenously twice daily for 30 days, open label. They reported a 42% decline in disability.
Hauser and colleagues then ran a randomized, double-blind version: 1,400 mg intravenously three times a week for four weeks, 11 patients on glutathione and 10 on placebo. There were no significant differences in the disease rating scale.
This is the standard shape of a disappointing result, and it is worth recognizing. A small open-label study reports a large effect. A randomized, blinded study with a higher dose reports none. The second design is the stronger one, and its dose was more than twice the first. Nobody has since run a larger version.
The skin-lightening question
The single most-searched use of injected glutathione is skin lightening, and it is the one the FDA has acted on. The agency states plainly that it has not approved any injectable drugs for skin whitening or lightening, and it obtained a court order against a company selling unapproved injectable products containing glutathione among other ingredients.
The randomized evidence that does exist for pigmentation is a combination of topical and oral glutathione over eight weeks in 46 participants, which reported a lower melanin index than placebo. We could not confirm the oral amount that trial used, so we do not publish one. The skin-lightening evidence goes through it in detail.
What if you already have a number?
Glutathione is sold in far larger vials than the peptides around it — grams rather than milligrams.
Turning a figure into a syringe volume is arithmetic, and the peptide calculator does it from the vial strength and the volume of diluent. That part always works.
Which is the trap. A calculator converts an unsourced number as cleanly as a sourced one. The output looks equally precise either way. Concentration mistakes scale accordingly, so check the arithmetic rather than assume it.
What is checkable
One thing that matters more here than almost anywhere else: reduced glutathione and its oxidized dimer are different substances with different registry numbers, and only the reduced form is what the literature above studied.
A certificate of analysis that names the form as well as the purity is the minimum. How to read a COA, the complete guide and where to buy glutathione cover it, and the peptide dosage chart holds the library.
Glutathione
Research-use-only material, sold by the vial with batch documentation. Check the certificate of analysis against the batch you receive.
What to know now
- Oral doses studied are 250 mg, 500 mg twice daily, 1,000 mg daily and a single 3 g dose. The trials do not agree on what they achieved.
- The six-month trial in 54 adults reported body stores rising 30 to 35% at 1,000 mg a day.
- A single 3 g oral dose raised nothing measurable in plasma over 270 minutes.
- Intravenous doses studied are 600 mg twice daily and 1,400 mg three times weekly, in Parkinson's disease.
- The randomized intravenous trial found no significant benefit.
- The FDA has not approved any injectable drug for skin lightening.
What we're watching
A properly powered trial of intravenous glutathione for any indication would be welcome, because the field currently rests on 9 patients open-label and 21 randomized. Neither is enough to settle anything.
On the oral side, the interesting open question is whether raised body stores mean anything functionally. Richie measured the stores; nobody has yet shown what filling them does.
Frequently asked questions
What oral glutathione doses have been studied?
250 mg and 1,000 mg a day for six months in 54 adults, 500 mg twice daily for four weeks in 40, and a single 3 g dose in 7. The results do not all agree.
Does oral glutathione raise glutathione levels?
It depends which measure and which trial. The six-month study reported body stores rising 30 to 35% at the high dose. A four-week study found no significant change in glutathione status or oxidative stress markers. A single 3 g dose raised nothing measurable.
What intravenous glutathione doses have been studied?
600 mg twice daily for 30 days in 9 Parkinson's patients, open label, and 1,400 mg three times a week for four weeks in a randomized trial of 21. The open-label study was positive; the randomized one was not.
Is injectable glutathione approved?
No. The FDA states that it has not approved any injectable drugs for skin whitening or lightening, and has acted against sellers of unapproved injectable products containing glutathione.
Why do glutathione doses vary so much?
Because the routes and the endpoints are different questions. Raising body stores over months, changing oxidative stress markers in weeks, and treating a neurological condition intravenously are three separate problems with three separate literatures.
References
- Witschi, A., Reddy, S., Stofer, B., & Lauterburg, B. H. (1992). The systemic availability of oral glutathione. European Journal of Clinical Pharmacology, 43(6), 667–669. https://doi.org/10.1007/BF02284971
- Richie, J. P., Jr., Nichenametla, S., Neidig, W., et al. (2015). Randomized controlled trial of oral glutathione supplementation on body stores of glutathione. European Journal of Nutrition, 54(2), 251–263. https://doi.org/10.1007/s00394-014-0706-z
- Allen, J., & Bradley, R. D. (2011). Effects of oral glutathione supplementation on systemic oxidative stress biomarkers in human volunteers. Journal of Alternative and Complementary Medicine, 17(9), 827–833. https://doi.org/10.1089/acm.2010.0716
- Wahab, S., Anwar, A. I., Zainuddin, A. N., et al. (2021). Combination of topical and oral glutathione as a skin-whitening agent: a double-blind randomized controlled clinical trial. International Journal of Dermatology, 60(8), 1013–1018. https://doi.org/10.1111/ijd.15573
- Sechi, G., Deledda, M. G., Bua, G., et al. (1996). Reduced intravenous glutathione in the treatment of early Parkinson's disease. Progress in Neuro-Psychopharmacology and Biological Psychiatry, 20(7), 1159–1170. https://doi.org/10.1016/s0278-5846(96)00103-0
- Hauser, R. A., Lyons, K. E., McClain, T., Carter, S., & Perlmutter, D. (2009). Randomized, double-blind, pilot evaluation of intravenous glutathione in Parkinson's disease. Movement Disorders, 24(7), 979–983. https://doi.org/10.1002/mds.22401
- U.S. Food and Drug Administration. (2019). FDA in brief: FDA warns against use of glutathione injections for skin lightening due to safety concerns. https://www.fda.gov/news-events/fda-brief/fda-brief-fda-warns-against-use-injectable-skin-lightening-and-skin-bleaching-products
- Lu, S. C. (2013). Glutathione synthesis. Biochimica et Biophysica Acta, 1830(5), 3143–3153. https://doi.org/10.1016/j.bbagen.2012.09.008
- Forman, H. J., Zhang, H., & Rinna, A. (2009). Glutathione: Overview of its protective roles, measurement, and biosynthesis. Molecular Aspects of Medicine, 30(1–2), 1–12. https://doi.org/10.1016/j.mam.2008.08.006
The oral dose used in the 2021 pigmentation trial is not in the reachable record, so that cell is left empty rather than estimated.