What is glutathione?

Glutathione is an endogenous tripeptide antioxidant, gamma-glutamyl-cysteinyl-glycine, that cells build from three amino acids in two enzyme steps. It is present in all mammalian tissues. Lu's 2013 review calls it the most abundant non-protein thiol in those tissues, and the reduced form (GSH) accounts for more than 98% of the total. ^[1] Inside cells its concentration sits in the range of 1 to 10 mM, with most cells near 1 to 2 mM and liver cells near 10 mM. In plasma it falls to the micromolar range. ^[2]

Two names cause most of the confusion. GSH is the reduced molecule, with a free thiol (-SH) on the cysteine. GSSG is the oxidised form, two glutathione molecules joined by a disulfide bond. ^[9] The "G" in both abbreviations stands for glutathione as a whole, and has nothing to do with the one-letter code for glycine. ^[9]

One common error is worth correcting early. Several consumer summaries list glutamine as a building block. The constituent is glutamate, and the first enzyme step joins glutamate to cysteine. ^[1] A 1500mg glutathione vial is in stock with a batch certificate.

Glutathione works as a reducing agent and an enzyme substrate: its cysteine thiol donates electrons, and several enzyme families use it to neutralise oxidants and bind reactive compounds. Lu's review states that its antioxidant function runs largely through glutathione peroxidase (GPx), which reduces hydrogen peroxide and lipid peroxides as GSH is oxidised to GSSG. GSSG reductase then converts GSSG back to GSH at the expense of NADPH. ^[1]

Forman's 2009 review groups the protective roles into two chemical jobs: ^[2]

• Reduction. GSH removes oxidants such as hydrogen peroxide through peroxidase reactions.
• Conjugation. Glutathione S-transferases (GSTs) attach GSH to electrophiles, such as the lipid breakdown product 4-hydroxynonenal, which marks them for removal.

The same reviews list further roles: storage of cysteine, maintenance of redox potential, regulation of cell proliferation and apoptosis, and modulation of immune function. ^[1] Glutathione also joins protein cysteines through S-glutathionylation, a reversible modification that cells use to protect and regulate thiol proteins under oxidative stress. ^[9]

Chemistry sets the limits. The cysteine thiol has a pKa of around 8.3, and inside the cytosol the GSH to GSSG ratio stays very high even during oxidative stress. ^[2] Researchers read a falling GSH to GSSG ratio as a marker of oxidative stress, which is why several of the human trials below measure that ratio. ^[5]

Glutathione is a three-residue peptide, gamma-L-glutamyl-L-cysteinyl-glycine, with one unusual bond: the glutamate links to cysteine through its gamma-carboxyl group. Lu's review notes that the only enzyme able to cut this bond is gamma-glutamyltranspeptidase (GGT), found on the outer surface of certain cells, so glutathione resists breakdown inside cells. ^[1]

The identifiers and properties come from PubChem ^[4] and the Human Metabolome Database. ^[10] We checked each value on 29 September 2026.

Two details matter when you read a certificate. First, "ECG" is shorthand. A standard peptide sequence implies alpha-linked residues, and glutathione's first bond is gamma-linked, which is why chemists write gamma-ECG. ^[9] Second, reduced and oxidised glutathione are different compounds with different masses. GSSG is two GSH molecules joined by a disulfide, so an identity result for reduced glutathione should correspond to about 307 g/mol.

Research on glutathione spans a century of biochemistry and a small set of human trials. The trials fall into four groups: oral supplementation and body stores, Parkinson's disease, cystic fibrosis and skin pigmentation. Most enrolled fewer than 60 people and ran for 3 months or less. Their results are mixed.

The oral trials disagree. Richie's 6-month trial reported mean glutathione increases of 30% to 35% in erythrocytes, plasma and lymphocytes in the larger-intake group. ^[5] Allen and Bradley's 4-week trial found total, reduced and oxidised glutathione unchanged. ^[6] The two trials differ in length, size and measurement sites, so neither settles the question alone.

The skin work has been reviewed twice. A 2019 systematic review included four studies and called the evidence inconclusive because of study quality and inconsistent findings. ^[17] A 2025 systematic review reported five randomised trials and one open-arm study of oral glutathione with significant reductions in melanin index against placebo, and one placebo-controlled study of IV glutathione. ^[18]

The biochemistry is older than any of these trials. Frederick Gowland Hopkins published "On an Autoxidisable Constituent of the Cell" in the Biochemical Journal in 1921, ^[19] and his 1925 follow-up carries the name in its title: "Glutathione: Its Influence in the Oxidation of Fats and Proteins". ^[20] Harington and Mead reported a chemical synthesis of glutathione in 1935. ^[21]

The glutathione evidence base is broad in biochemistry and thin in controlled human outcomes. Four limits are worth stating plainly.

1. Trials are small and short. The largest trial in the table enrolled 153 people, and most ran 3 months or less. ^[12] A 2016 review found no study of long-term IV glutathione use for any indication. ^[7]
2. Placebo groups moved too. In the 2017 Parkinson's trial, all groups improved, including placebo, and the authors called the placebo response more robust than in previous studies. ^[14]
3. Delivery to a tissue is a separate question from an effect in it. Griese's cystic fibrosis trial measured more glutathione in sputum, and found no change in markers of oxidation, proteolysis or inflammation. ^[12]
4. The trials used their own study products. Purity and identity of a research vial are separate questions, and a batch certificate answers them.

Studies of glutathione have mostly reported no or minimal adverse effects, over short study periods. A 2016 review of trials across indications found that all had run a few IV sessions or 4 to 12 weeks, and none reported long-term IV use. ^[7] The route changes the reported profile.

• Oral, healthy women (12 weeks): the investigators reported no serious adverse effects throughout the study. ^[15]
• IV, Parkinson's disease (4 weeks): there were no withdrawals because of adverse events, and reported adverse events were similar in the glutathione and placebo groups. ^[11]
• Intranasal, Parkinson's disease (3 months): one participant in the higher-strength glutathione group developed cardiomyopathy. ^[14] The earlier phase I/IIa trial found no substantial differences in adverse events between groups. ^[13]
• Inhaled, cystic fibrosis (6 months): adverse event incidence was similar between glutathione and placebo. ^[12] A 2008 review of inhaled glutathione reported transient coughing and an unpleasant odour as common, and bronchoconstriction in asthma patients presumed to be sulfite-sensitive. ^[22]
• Skin studies: a 2019 systematic review reported some adverse events, all nonserious. ^[17] A 2025 systematic review concluded that "IV glutathione is contraindicated due to lack of efficacy and side effects". ^[18]

These are observations from specific study populations, reported as the published record. The 2016 review also warned that the absence of long-term data leaves chronic IV use unassessed. ^[7]

Glutathione for parenteral use is listed in Schedule 4 (prescription only) of the Poisons Standard. The entry reads "GLUTATHIONE for parenteral use" and sits in the June 2026 instrument (F2026L00633), which commenced on 1 June 2026. The instrument's index lists glutathione under Schedule 4 with no Appendix D entry. ^[3] The wording limits the entry to parenteral use, and our guide to Australian peptide law and the Poisons Standard explains what each schedule means.

For sport, glutathione is not named on the WADA 2026 Prohibited List, which took effect on 1 January 2026. The List's methods section applies whatever the substance: M2.2 prohibits intravenous infusions above a total of 100 mL per 12-hour period, outside hospital treatment, surgical procedures or clinical diagnostic investigations. ^[8] WADA revises the List every year, and Sport Integrity Australia is the body to check with.

Glutathione and NAD+ are both redox molecules sold in the longevity range, and they differ in chemistry, size and scheduling. Glutathione is a peptide of three amino acids. NAD+ is a dinucleotide coenzyme with no amino acids at all.

The glutathione column is drawn from the sources above. ^[4][3] The NAD+ column comes from the same PubChem, Poisons Standard and WADA checks we ran for each compound on 29 September 2026. Both take part in cellular redox reactions, and GSSG reductase regenerates glutathione at the expense of NADPH. ^[1] Our explainer on what NAD+ is covers its research record, and both compounds sit in our longevity research compounds range.

Glutathione arrives as a white solid, and its free thiol is the part that needs protecting: GSH oxidises to the disulfide GSSG. ^[4][9] We found no published stability study for research-grade glutathione, so the working rule is the one used for peptides generally: sealed, cold, dry and dark before reconstitution, and cold and dark afterwards. Our peptide storage guide covers temperatures, light, freeze-thaw and labelling.

Solubility shapes the solvent volume. The Human Metabolome Database records an experimental water solubility of 292.5 mg/mL. ^[10] At that figure, 1500mg of glutathione needs at least 5.1 mL of water to dissolve fully (1500 divided by 292.5). A 3 mL volume would imply 500 mg/mL, above the recorded solubility. We stock BAC Water, which is sterile water with 0.9% benzyl alcohol, in 3 mL vials. Our guide on how to reconstitute peptides explains how to calculate and label a concentration in mg per mL.

Peptides Collective sells glutathione for laboratory research use only, in 1500mg vials from A$118. Stock ships from Western Australia with tracking.

Every batch is tested by an independent lab before it goes on sale. The certificate reports purity by HPLC and identity by mass spectrometry, and it is published under the batch number printed on the vial. You can search the certificate of analysis library by that batch number and match the report to the vial in your hand.

Read the certificate against the structure table above. The identity result should correspond to reduced glutathione at about 307 g/mol, and a peak near twice that mass would point to the oxidised disulfide. Our guide on how to read a peptide certificate of analysis explains the HPLC trace and the mass spectrum. The glutathione product page links the certificate for the current batch.

Glutathione is a gamma-linked tripeptide of glutamate, cysteine and glycine, and cells use it as the main substrate for peroxide reduction and electrophile conjugation. Its human trial record is small, short and mixed, and no study has examined long-term IV use. In Australia, glutathione for parenteral use is a Schedule 4 substance, and WADA's 2026 List does not name it. For a research vial, the batch certificate is the evidence that settles what is in it.