What is glutathione? What it does, benefits and what the evidence shows

Glutathione is a three-amino-acid peptide that every cell in your body already makes, and it is one of the most abundant antioxidants in tissue. Supplementing it has been studied for real medical uses (protecting nerves during cisplatin chemotherapy is the best known) and for skin lightening, with small trials and mixed results. We found no FDA-approved glutathione drug, and FDA has warned twice, in 2019 and again in August 2026, about adverse events from compounded glutathione injectables made with supplement-grade powder that carried too much endotoxin.

What glutathione is and how it works

Glutathione (often written GSH) is described as an endogenously synthesized tripeptide (Mischley et al., Journal of Parkinson's Disease, 2017). It is found in all mammalian tissues as the most abundant non-protein thiol, and it defends cells against oxidative stress, helps detoxify foreign compounds, and takes part in redox signaling and immune function (Lu, Biochimica et Biophysica Acta, 2013). A review of its biology calls it the most abundant low-molecular-weight thiol made in cells, with roles in protecting against oxidative damage and in keeping the cell's redox balance steady (Forman et al., Molecular Aspects of Medicine, 2009).

Because your cells build it from scratch, the question for a buyer is different from most compounds in this series. Nobody disputes that glutathione matters. The open question is whether adding more from outside changes anything you can feel or measure, and that depends on what is being treated.

People take it three ways: as oral supplements, as intravenous infusions from wellness clinics, and as injectable vials from research-chemical sellers. The FDA notices below show the second one happening at outpatient clinics with compounded product. We describe what the trials tested, not what any route is best for.

What people use it for

What the research actually shows

Cisplatin nerve damage

The strongest older evidence is in cancer care. In a 1995 double-blind, placebo-controlled trial of 50 patients with advanced gastric cancer on a cisplatin-based regimen, glutathione was given alongside the chemotherapy. By week 15, 4 of 24 assessable patients on glutathione had neurotoxicity, against 16 of 18 on placebo, and nerve conduction tests agreed. The authors also reported that response rates were not lower with glutathione (Cascinu et al., 1995). A 1997 double-blind trial of 151 women with ovarian cancer found that more of them could complete six courses of cisplatin with glutathione (58% versus 39%), with better quality-of-life scores, and a trend toward better response that did not reach significance (Smyth et al., 1997).

Those trials are three decades old and small, and the field has not turned them into a recommendation. The American Society of Clinical Oncology's 2020 guideline update reconfirmed that no agents are recommended for preventing chemotherapy-induced peripheral neuropathy (Loprinzi et al., Journal of Clinical Oncology, 2020). The abstract does not name glutathione, so read that as the field's overall position rather than a verdict on this compound.

Raising your own levels

Whether swallowing glutathione does anything measurable was long doubtful. A six-month, randomized, double-blind, placebo-controlled trial in 54 healthy non-smoking adults found that glutathione in blood rose versus baseline and fell back after supplementation stopped. One treatment group also showed more than twice the natural killer cell cytotoxicity of placebo at three months (Richie et al., 2015). That shows a lab-value change in healthy people. It does not show that anyone felt or functioned better.

Skin lightening

Glutathione's ability to reduce melanin is why it turned into a cosmetic product, and this is where the hype runs furthest ahead of the data. A 2025 systematic review found five randomized trials and one open-label study of oral glutathione that reported a lower melanin index than placebo, and a combination of topical and oral glutathione that beat either alone. It found only one placebo-controlled study of intravenous glutathione, and the reviewers concluded that intravenous use is contraindicated because of lack of efficacy and side effects, describing the oral and topical effects as moderate and not sustained (Sarkar et al., 2025). One of those trials, an eight-week study of 46 people, found the topical-plus-oral combination lowered melanin index versus placebo (Wahab et al., International Journal of Dermatology, 2021).

An earlier review was harsher about the injected form. It described the intravenous evidence as a single study with a "dubious" design and flawed analysis, said parenteral glutathione is approved only for severe liver disorders and for preventing chemotherapy-related neurotoxicity, and pointed to advisories from regulators about its cosmetic use (Sonthalia et al., Dermatology Practical & Conceptual, 2018). The same review described the results from oral, sublingual and topical products as appreciable but reversible. Cosmetic outcomes here are measured with a colorimeter on small groups over weeks, so they say little about long-term safety.

Parkinson's disease

Glutathione is depleted early in Parkinson's disease, which made supplementing it an obvious idea. A randomized, double-blind pilot of intravenous glutathione in 21 people with Parkinson's found it well tolerated with similar adverse events to placebo, and no significant difference in rating scores; the authors suggested a possible mild symptomatic effect that a larger study would have to test (Hauser et al., 2009). A 45-person phase IIb trial of intranasal glutathione found that everyone improved, including the placebo group, and that neither dose group beat placebo; one participant in the higher-dose group developed cardiomyopathy (Mischley et al., 2017). Neither trial showed a benefit over placebo.

Side effects and risks

• Contamination, not the molecule, is the documented problem. On February 1, 2019, FDA warned compounders not to use one distributor's supplement-grade glutathione powder for sterile injectables after reports of adverse events in seven clinic patients, including nausea, vomiting, chills and, in one patient, low blood pressure and difficulty breathing that led to hospital transfer. FDA's lab found excessive bacterial endotoxin in the samples it tested, some at up to five times the appropriate limit (FDA, "FDA highlights concerns with using dietary ingredient glutathione to compound sterile injectables").
• It happened again in 2026. An FDA notice dated August 27, 2026 describes reports of at least 30 patients with adverse events after intravenous glutathione compounded by different pharmacies from one lot of dietary-supplement-grade powder. Reported events included fever, chills, pain, dizziness, and signs of shock and sepsis-like symptoms, some leading to hospitalization, and two Texas pharmacies recalled injectables for elevated endotoxin. FDA said it was still investigating (FDA, "FDA reminds compounders not to use dietary supplement grade glutathione for injectables"). Worth knowing as a buyer: a purity or quantity result does not measure endotoxin, which is a separate test (endotoxin in research peptides).
• In trials. Glutathione was generally well tolerated in the trials above, with adverse events similar to placebo in the Parkinson's pilot. The single cardiomyopathy case in the intranasal trial is reported without a stated cause.
• Long-term effects are unknown. The trials ran from weeks to about six months. We found no long-term safety data for supplementing glutathione, and no controlled data on the cosmetic injectable use.
• Approval status. A search of DailyMed for "glutathione" returned 57 labels, and none is an injectable glutathione drug. They are homeopathic, cosmetic and similar listings, plus a balanced salt solution for eye surgery that contains glutathione. FDA's list of bulk drug substances nominated for compounding, updated May 14, 2026, places glutathione in Category 1, substances under evaluation, and does not list it in the significant-safety-risk category. That means FDA has not decided on it, not that it has approved or cleared it.

What the lab tests show

As of September 29, 2026, VendorVerify's database has only 2 glutathione vials, from 2 vendors, with lab reports dated December 2024 and May 2025. Both measured 99.90% and 99.91% pure. On quantity, one came in about 1% over its label and the other about 40% over. Under our failure definition (empty, under 95% pure, more than 20% under label, or more than 50% over), neither failed. Two vials cannot say anything about how vendors in general do on glutathione, and the figures cover purity and fill amount, not sterility or endotoxin.

Because we don't have enough lab data on this compound to rank vendors for it, here are the highest-ranked vendors across all compounds right now. A vendor's overall record is a signal, not a guarantee for a compound they have never had tested.

Buying smarter

Look at each vendor's full record and how many reports sit behind the score, and check the glutathione results page for any new reports. Given the FDA cases, the most useful add-on for an injectable vial is the endotoxin test; how to get a peptide tested covers ordering identity, purity, quantity and endotoxin from an independent lab, and how to read a peptide COA and fake peptide COAs cover what to check on a report you didn't commission. A 40% overfill like the one above is also worth understanding; underdosed and overfilled peptides explains why the label number can be off in either direction.

If a report comes back with a fail, stop using that batch, tell anyone who bought from the same run, bring the report to the vendor, and submit it to VendorVerify. Readers looking at antioxidant compounds also tend to read about NAD+ and SS-31; the peptide hub lists every compound we track.

Database figures are from VendorVerify as of September 29, 2026. This isn't medical advice; glutathione has no FDA-approved injectable product that we could find, and FDA has warned about contaminated compounded glutathione injectables.