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Glutathione

Endogenous antioxidant tripeptide

Also known as GSH, L-glutathione, reduced glutathione

The body's main intracellular antioxidant, sold widely as an injectable and oral skin-lightening agent. The biology is not in question. The cosmetic claim rests on small trials, and the injectable route on none.

What doses have been studied? What each trial gave, with the population it was given to.

Guide updated Oct 22, 2026Literature checked Oct 21, 20264 curated studies55 literature recordsBaseline editorial
Sequencegamma-Glu-Cys-Gly

Overview

In shortThe body's main built-in antioxidant, made by nearly every cell. That part is settled biology. It is here because it is sold at huge scale as an injectable and oral skin-lightening drip, and that market has very little to do with the biology behind it.

Glutathione is a tripeptide of glutamate, cysteine and glycine, made by essentially every cell in the body. It is the dominant intracellular antioxidant and a required cofactor for the enzymes that neutralize peroxides and conjugate toxins for excretion. None of that is disputed, and it is why the compound appears in serious clinical research across liver disease, neurodegeneration and chemotherapy toxicity.

It is in this catalog for a different reason. Glutathione is sold at very large scale as an intravenous "skin brightening" and "detox" drip, and as an oral supplement making the same claim. That market has almost nothing to do with the biology above, and the gap between the two is the entry.

Mechanism

In shortIts antioxidant job is established chemistry. The skin-lightening claim is a separate proposal: that it pushes pigment production toward a lighter type. That happens in a dish, and whether it happens in human skin from swallowing or infusing it is the open question. Being a peptide, an oral dose also meets the same digestive enzymes any peptide does.

Two mechanisms are proposed and they are not equally supported.

The antioxidant role is established biochemistry: glutathione donates a reducing equivalent, is oxidized to GSSG, and is recycled by glutathione reductase. It is a cofactor rather than a drug in this role.

The skin-lightening claim rests on a separate proposal, that glutathione shifts melanin synthesis away from dark eumelanin toward lighter phaeomelanin, partly by interfering with tyrosinase. That effect is observable in cell culture. Whether it happens in human skin at concentrations achievable by swallowing or infusing the peptide is the open question, and it is the one the marketing skips.

The bioavailability problem sits underneath everything. Glutathione is a peptide, and an oral dose meets the same digestive enzymes any peptide meets.

Evidence

In shortThinnest exactly where the market is biggest. One small placebo-controlled trial of oral glutathione reported a change in skin pigment over four weeks, and later reviews called the overall evidence limited and at real risk of bias. For the intravenous drip, the most expensive and most sold form, there is no properly sized evidence for a cosmetic result at all.

Thin, and thinnest exactly where the market is largest.

For skin lightening, a randomized double-blind placebo-controlled trial of oral glutathione reported a change in melanin index over four weeks. It is small, short, and in one population. Systematic reviews since have found the overall body of work limited, heterogeneous and at meaningful risk of bias, and have declined to conclude that the effect is established.

For whether oral dosing raises body stores at all, a randomized trial addressed the question directly rather than assuming it, which is more than most of this literature does.

For the intravenous route, which is the most commonly sold and most expensive form, there is no adequately powered randomized evidence for a cosmetic outcome. That is the sharpest fact in this entry: the version people pay the most for is the version with the least behind it.

Safety

In shortTaken by mouth it is generally well tolerated, and that gets used to imply the injectable version is equally safe. It does not follow. Injecting brings infusion reactions plus the infection risk of any product made outside pharmaceutical standards. Several national regulators have warned specifically against IV glutathione sold for skin lightening.

As an endogenous molecule taken orally, glutathione is generally well tolerated, and that tolerability is routinely used to imply the injectable route is equally benign. It does not.

Intravenous administration is a different exposure with different risks: infusion reactions, and the infection and contamination risks that belong to any injected product prepared outside pharmaceutical manufacturing. Several national regulators have issued public warnings specifically about intravenous glutathione marketed for skin lightening, on the grounds that it is unapproved for that use and that the products involved are frequently unlicensed. Reports of serious harm, including Stevens-Johnson syndrome and kidney injury, exist in that context.

There is also a category error worth naming. Skin lightening is not a medical outcome, and a product sold for it is being used cosmetically at a dose and route nobody has established.

Regulatory status

In shortApproved in some countries as an injection for specific medical uses, and sold widely as an oral supplement under food rules, which means its cosmetic claims are never assessed the way a medicine's would be. Not approved anywhere for skin lightening.

Approved in some jurisdictions as an injectable for specific clinical indications, and widely available as an oral supplement under food rules rather than drug rules, which means its cosmetic claims are not assessed the way a medicine's would be.

Not approved anywhere for skin lightening. Regulators including the Philippine FDA and others have issued explicit advisories against intravenous glutathione sold for that purpose. Its legal status therefore differs sharply depending on the route and the claim, and a single sentence about whether glutathione is "legal" is meaningless without both.

The literature

4 studies indexed. Findings and limitations get equal weight, on purpose.

Always check the primary source

Members area

The Glutathione literature needs an account

Everything above is free to read. What an account opens is the evidence underneath it: 4 studies with their limitations, and the regimen each trial actually reported.

  • Every study, with what it found and what it cannot show
  • The limitations, given the same weight as the findings
  • The dose each named trial administered, where recorded
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The wider literature

28 indexed papers and 27 registered trials mentioning Glutathione, straight from PubMed and ClinicalTrials.gov. 17 of 27 administer it; the rest measure it. These have not been read by us. Unlike the studies above, they carry no findings and no limitations written by anyone here, because writing either would mean claiming a reading nobody has done. They are a starting point for yours.

Registered trials (27)

  1. Efficacy Evaluation Study of Vitamin C and Glutathione Liquid Sachet

    TCI Co., Ltd.2026NCT07379216

    interventionalnarecruitingn=30

  2. GABA and GSH in FRDA

    Children's Hospital of Philadelphia2024NCT07635030

    observationalenrolling by invitationn=60

  3. INTERCEPT Safety Evaluation on Whole Blood

    Swiss Transfusion SRC2024NCT04020224

    interventionalnawithdrawnn=0

  4. Cognitive Analytic-Informed Guided Self-help for Depression

    University of Sheffield2022NCT05344326

    interventionalnaunknownn=13

  5. Glutathione (GSH) Supplementation After Hospitalization

    Emory University2022NCT03166371

    interventionalnawithdrawnn=0

  6. Multifamily Guided Self-Help Family-Based Treatment (MF-GSH-FBT)

    Stanford University2022NCT05446038

    interventionalnacompletedn=17

  7. Evaluation of the Relationship Between Oxidative Stress and Human Reproduction

    Calla IVF Center2021NCT05575739

    observationalunknownn=80

  8. SH-SS and GSH-GSSG Homeostasis in Post-stroke Patients

    Abant Izzet Baysal University2020NCT04884555

    observationalcompletedn=77

  9. Signaling Pathways Targeting Colorectal Cancer in Egypt

    Assiut University2018NCT03467308

    observationalcompletedn=180

  10. Correction of Neonatal Glutathione by N-acetylcysteine in Pregnant Women at Risk of Premature Birth (GSH MAP)

    Nantes University Hospital2018NCT03596125

    interventionalphase2phase3terminatedn=39

  11. Efficacy of Na-GST-1/Alhydrogel Hookworm Vaccine Assessed by Controlled Challenge Infection

    Baylor College of Medicine2018NCT03172975

    interventionalphase2completedn=39

  12. Alpha-Glutathione-S-Transferase (AlphaGST) and MARINA Index in Metabolic-Dysfunction-Associated-Steatotic-Liver-Disease (MASLD)

    University of Campania Luigi Vanvitelli2017NCT05804955

    observationalcompletedn=260

  13. The Role of Oral Glutathione on Growth Parameters in Children With Cystic Fibrosis

    University of Minnesota2017NCT03020719

    interventionalphase2completedn=60

  14. Dual Hypothermic Oxygenated Perfusion of DCD Liver Grafts in Preventing Biliary Complications After Transplantation

    Robert J. Porte2016NCT02584283

    interventionalphase3completedn=157

  15. Phase IIb Study of Intranasal Glutathione in Parkinson's Disease

    Bastyr University2015NCT02424708

    interventionalphase2completedn=45

  16. The Effects of N-acetylcysteine on Performance and Redox Homeostasis

    Aristotle University Of Thessaloniki2015NCT03121222

    interventionalphase2completedn=36

  17. Vitamin B-6 and Glutathione on Inflammation, Homocysteine, Oxidative Stress and Antioxidant Capacities

    Taichung Veterans General Hospital2014NCT02321579

    interventionalnaunknownn=25

  18. Restoring Glutathione Synthesis With Tecfidera: An in Vivo H-MRS Single-Arm Study at 7T in Patients With RR MS

    Yale University2014NCT02218879

    observationalterminatedn=7

  19. Safety and Immunogenicity Study of Na-GST-1 With or Without CpG

    Baylor College of Medicine2014NCT02143518

    interventionalphase1completedn=24

  20. Glutathione and Function in HIV Patients

    Baylor College of Medicine2014NCT02348775

    interventionalphase1completedn=16

  21. Glutathione and Health With Post-Polio Syndrome

    University of Michigan2011NCT01402570

    interventionalnacompletedn=20

  22. An Open-label, Phase I/IIa, Dose Escalating Study of 2B3-101 in Patients With Solid Tumors and Brain Metastases or Recurrent Malignant Glioma.

    BBB-Therapeutics B.V.2011NCT01386580

    interventionalphase1phase2completedn=84

  23. Role of HIV on Glutathione Synthesis and Oxidative Stress

    Baylor College of Medicine2010NCT01355198

    interventionalphase1completedn=10

  24. Oral Glutathione Supplementation on the Levels of Blood Glutathione

    Milton S. Hershey Medical Center2010NCT01044277

    interventionalnacompletedn=61

  25. Study of Oral Darinaparsin in Patients With Advanced Solid Tumors

    Alaunos Therapeutics2010NCT01139346

    interventionalphase1completedn=12

  26. Cysteine Supplementation in Critically Ill Neonates

    University of California, Los Angeles2006NCT00254176

    interventionalphase2phase3unknownn=108

  27. Treating Oxidative Stress in Children With Autism

    Arkansas Children's Hospital Research Institute2006NCT00692315

    interventionalnacompletedn=40

Papers (28)

  1. Targeting Reduced Glutathione (GSH) to Promote Metabolic Health: Insights on the Role of Bioactive-Rich Foods and Fasting Protocols.

    Vardakas P, et al.International journal of molecular sciences2026PMID 42511748

    journal articlereview

  2. Glutathione as a taste modulator: molecular mechanisms of interaction with umami and sweet taste receptors.

    Cornut C, et al.Food chemistry. Molecular sciences2025PMID 41246561

    journal article

  3. Reduced glutathione ameliorates sepsis-induced acute kidney injury in mouse model: involvement of cuproptosis.

    Wang L, et al.Renal failure2025PMID 40545999

    journal article

  4. Glutathione Therapy in Diseases: Challenges and Potential Solutions for Therapeutic Advancement.

    Dehkordi HT, et al.Current molecular medicine2024PMID 37594114

    reviewjournal article

  5. Efficient production of l-glutathione by whole-cell catalysis with ATP regeneration from adenosine.

    Zuo S, et al.Biotechnology and bioengineering2024PMID 38629468

    journal article

  6. Studies on the Complexation of Platinum(II) by Some 4-Nitroisoxazoles and Testing the Cytotoxic Activity of the Resulting Complexes.

    Mastalarz H, et al.Molecules (Basel, Switzerland)2023PMID 36770951

    journal article

  7. Reduced Glutathione-Modified Electrode for the Detection of Hydroxyl Free Radicals.

    Ghaedamini H, et al.Biosensors2023PMID 36832020

    journal article

  8. Mechanism of Reduced Glutathione Induced Lysozyme Defolding and Molecular Self-Assembly.

    Guo D, et al.Foods (Basel, Switzerland)2023PMID 37238749

    journal article

  9. Exogenous supplementation of Sulfur (S) and Reduced Glutathione (GSH) Alleviates Arsenic Toxicity in Shoots of Isatis cappadocica Desv and Erysimum allionii L.

    Arianmehr M, et al.Environmental science and pollution research international2022PMID 35469387

    journal article

  10. The effects of the oral supplementation of L-Cystine associated with reduced L-Glutathione-GSH on human skin pigmentation: a randomized, double-blinded, benchmark- and placebo-controlled clinical trial.

    Duperray J, et al.Journal of cosmetic dermatology2022PMID 33834608

    journal articlerandomized controlled trial

  11. The Selenoprotein Glutathione Peroxidase 4: From Molecular Mechanisms to Novel Therapeutic Opportunities.

    Weaver K, et al.Biomedicines2022PMID 35453641

    journal articlereview

  12. Addition of Reduced Glutathione (GSH) to Freezing Medium Reduces Intracellular ROS Levels in Donkey Sperm.

    Yánez-Ortiz I, et al.Veterinary sciences2021PMID 34941829

    journal article

  13. Reduced Glutathione Mediates Pheno-Ultrastructure, Kinome and Transportome in Chromium-Induced Brassica napus L.

    Gill RA, et al.Frontiers in plant science2017PMID 29312362

    journal article

  14. Redox-implications associated with the formation of complexes between copper ions and reduced or oxidized glutathione.

    Aliaga ME, et al.Journal of inorganic biochemistry2016PMID 26277412

    journal articleresearch support, non-u.s. gov'treview

  15. Oral reduced L-glutathione improves growth in pediatric cystic fibrosis patients.

    Visca A, et al.Journal of pediatric gastroenterology and nutrition2015PMID 25633497

    journal articlerandomized controlled trialresearch support, non-u.s. gov't

  16. Measurement of oxidized/reduced glutathione ratio.

    Owen JB, et al.Methods in molecular biology (Clifton, N.J.)2010PMID 20700719

    journal article

  17. Electrocatalysis of reduced L-glutathione oxidation by iron(III) tetra-(N-methyl-4-pyridyl)-porphyrin (FeT4MPyP) adsorbed on multi-walled carbon nanotubes.

    Luz RC, et al.Talanta2008PMID 18761161

    journal articleresearch support, non-u.s. gov't

  18. Essential requirement of reduced glutathione (GSH) for the anti-oxidant effect of the flavonoid quercetin.

    Ferraresi R, et al.Free radical research2005PMID 16298752

    journal articleresearch support, non-u.s. gov't

  19. Erythrocytes as carriers of reduced glutathione (GSH) in the treatment of retroviral infections.

    Fraternale A, et al.The Journal of antimicrobial chemotherapy2003PMID 12972455

    journal articleresearch support, non-u.s. gov'treview

  20. Measurement of reduced glutathione (GSH) in human brain using LCModel analysis of difference-edited spectra.

    Terpstra M, et al.Magnetic resonance in medicine2003PMID 12815674

    clinical trialjournal articleresearch support, non-u.s. gov'tresearch support, u.s. gov't, p.h.s.

  21. S-Adenosyl-L-methionine and mitochondrial reduced glutathione depletion in alcoholic liver disease.

    Fernández-Checa JC, et al.Alcohol (Fayetteville, N.Y.)2002PMID 12163147

    journal articleresearch support, non-u.s. gov'tresearch support, u.s. gov't, p.h.s.review

  22. Blood reduced glutathione (GSH) concentrations in healthy and ill subjects.

    Ruocco L, et al.Minerva medica2001PMID 11317135

    comparative studyjournal article

  23. Augmentation of mitochondrial reduced glutathione by S-adenosyl-L-methionine administration in ischemia-reperfusion injury of the rat steatotic liver induced by choline-methionine-deficient diet.

    Kaneshiro Y, et al.European surgical research. Europaische chirurgische Forschung. Recherches chirurgicales europeennes1998PMID 9493692

    journal articleresearch support, non-u.s. gov't

  24. Antioxidant activity of metallothionein compared with reduced glutathione.

    Miura T, et al.Life sciences1997PMID 9155005

    comparative studyjournal article

  25. Compatibility of reduced glutathione (GSH) with different solutions currently used in anesthesia and reanimation.

    Mangiameli S, et al.Minerva anestesiologica1995PMID 9019670

    journal article

  26. Superoxide-dependent depletion of reduced glutathione by L-DOPA and dopamine. Relevance to Parkinson's disease.

    Spencer JP, et al.Neuroreport1995PMID 7579129

    journal articleresearch support, non-u.s. gov't

  27. Effect of reduced glutathione (GSH) on pharmacokinetics and distribution of rifamycin SV in rats.

    Leszczyńska ABiochemical pharmacology1981PMID 7213413

    journal article

  28. ERYTHROCYTIC REDUCED GLUTATHIONE (GSH) AND GLUCOSE 6-PHOSPHATE DEHYDROGENASE (G-6-PD) ACTIVTY IN THALASSAEMIA TRAIT AND HB. E-TRAIT.

    SWARUP S, et al.Bulletin of the Calcutta School of Tropical Medicine1963PMID 14299484

    journal article

Discussion

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For Research & Educational Discussion Only. Not Medical Advice

This guide is educational reference material compiled from published literature. It is not medical advice, not a recommendation, and not a substitute for a clinician who knows your history. Nothing here should be used to make a decision about your own health without one.

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