Glutathione
Antioxidant, Detoxification
In short
- The body's principal intracellular antioxidant tripeptide — an endogenous molecule, not a synthetic one.
- Oral bioavailability is the central problem: it is largely broken down in the gut into its constituent amino acids.
- This is why NAC is often the more practical route to raising glutathione than glutathione itself.
- Widely used intravenously for skin lightening, particularly in Asia, where regulators have issued explicit safety warnings.
- The FDA has warned against injectable glutathione products for skin lightening.
Structure
How it works
Glutathione is a tripeptide (glutamate-cysteine-glycine) present in nearly every cell, where it neutralises reactive oxygen species, supports phase II detoxification by conjugating xenobiotics, and maintains the redox state of protein thiols.
Cysteine availability is normally the rate-limiting factor for its synthesis, which is the pharmacological basis for supplying NAC instead.
Orally administered glutathione is substantially hydrolysed in the gastrointestinal tract, so raising intracellular glutathione by eating it is inefficient — some studies of liposomal and sublingual forms report better results, and the literature is mixed.
What the research shows
Some studies of oral and liposomal glutathione report increases in body stores over weeks; others show little effect. The evidence is genuinely inconsistent.
Intravenous glutathione produces transient plasma elevation, which is the basis for its cosmetic use.
Skin lightening: glutathione inhibits tyrosinase and shifts melanin synthesis toward the lighter pheomelanin. Effects are reported but evidence quality is poor, and the practice is the subject of regulatory warnings.
Studies in Parkinson disease have explored intravenous administration with limited results.
Dosing in the literature
Figures below are quoted from published studies, with the species or population they were measured in. They are records of what was studied, not recommendations.
| Studied in | Amount | Route | Source |
|---|---|---|---|
| Human — oral supplementation studies of body stores | 250–1,000 mg daily over weeks to months | oral | PubMed |
| Human — intravenous studies (including Parkinson disease) | Varies widely; see source | intravenous | PubMed |
Commonly reported ranges
These are amounts people report using. They are not from any study, have not been evaluated for safety, and are reproduced here only because they circulate widely and are better seen alongside the evidence than instead of it.
| Reported by | Amount | Route |
|---|---|---|
| Commonly reported | 250–1,000 mg daily orally; injectable protocols vary widely | oral, sublingual, or injected |
The oral route is limited by gastrointestinal breakdown, so dose does not translate straightforwardly to tissue levels. Injectable use for cosmetic purposes is the subject of explicit FDA and other regulatory warnings, and unregulated injectable products are the specific concern.
Handling and storage
Oral capsules, liposomal preparations, and sublingual forms are all sold, with liposomal and sublingual marketed as addressing the bioavailability problem — with mixed supporting evidence.
For most purposes NAC is the better-evidenced and cheaper route to raising glutathione, because it supplies the rate-limiting substrate rather than the finished molecule.
Side effects
Oral use is generally well tolerated, with occasional bloating or cramping.
The safety concern is injectable use. The FDA has warned about injectable skin-lightening products containing glutathione, citing risks including infection from unsterile compounding and unknown effects of high-dose systemic administration. Serious adverse events including Stevens-Johnson syndrome and renal impairment have been reported in the cosmetic-injection context.
Inhaled glutathione can trigger bronchospasm in asthmatics.
Combinations
Commonly combined with vitamin C, which regenerates oxidised glutathione, and with NAC, which supplies the rate-limiting precursor — the latter combination is mechanistically sensible.
The blunting of exercise-induced training adaptation by high-dose antioxidants applies here as it does to NAC.
Research status
Glutathione biology is fundamental and extensively studied. Glutathione supplementation as an intervention is far less well supported, and the bioavailability question is unresolved after decades.
The cosmetic injection literature is poor quality and commercially driven.
Legal status
Available as a dietary supplement in most jurisdictions. Injectable glutathione for skin lightening is not approved and is the subject of FDA warnings; several countries including the Philippines have issued specific advisories.
WADA status
Not on the WADA Prohibited List. Sold as a dietary supplement rather than a drug, so the S0 unapproved-substance clause does not apply. Note that supplement contamination is a recognised source of inadvertent doping violations, and third-party batch testing is the only real mitigation.
Conclusion
Glutathione is unquestionably important biology and a poor drug — the molecule you want inside cells is the one your gut is best at taking apart.
If the goal is raising glutathione, NAC has better evidence and better economics. If the goal is skin lightening by injection, that is the use regulators have specifically warned about.
Sources
Track your own Glutathione protocol
Peppers logs your doses, models your levels from this half-life, tracks your vials and tells you when you will run out. Free on iPhone.
Reference and educational information only. Not medical advice. Nothing here diagnoses, treats, or prescribes, and nothing here is a recommendation to use any compound. The compounds described are research chemicals and are not approved for human consumption. Legal and anti-doping status change — the review date above is when these claims were last checked. Talk to a qualified clinician about anything you intend to take.