Glutathione

What is glutathione and what does it do in the body?

Glutathione (GSH) is a three-amino-acid (tripeptide) molecule synthesized in the body that captures free radicals. Allen and Bradley write that GSH is the most abundant endogenously synthesized free radical scavenger in humans and that there is growing mechanistic, clinical, and epidemiological evidence that GSH status is important in acute and chronic diseases. ^[2] Sonthalia and colleagues describe glutathione as a low-molecular-weight thiol-tripeptide that plays a prominent role in intracellular redox balance; it is found in the reduced form in the cell. ^[8]

Because glutathione is produced by the body, it is not an essential nutrient like a vitamin or mineral, and there is no defined requirement or deficiency threshold for supplementation. The question under discussion is therefore whether orally taken glutathione increases body stores and whether this leads to a measurable health outcome. Richie and colleagues write, as the purpose of their study, that oral GSH has been shown to be bioavailable in animal models but that its efficacy in humans had not been demonstrated. ^[1] Dilokthornsakul and colleagues report that the clinical efficacy of the oral form is still questioned because of limited absorption and bioavailability. ^[5]

Does oral glutathione raise blood glutathione levels?

In the 6-month, double-blind, placebo-controlled RCT by Richie and colleagues, 54 non-smoking adults received 250 or 1,000 mg of oral GSH per day or placebo. Blood GSH levels increased from baseline at months 1, 3, and 6 at both doses. At month 6 in the high-dose group, mean GSH increased by 30–35% in erythrocytes, plasma, and lymphocytes and by 260% in buccal cells; in the low-dose group, a 17% increase in blood and a 29% increase in erythrocytes were found. The increases were mostly dependent on dose and duration, and levels returned to baseline after a one-month washout period. In both dose groups, the oxidized/reduced glutathione ratio in whole blood decreased at month 6. ^[1] Two commentary articles are recorded in PubMed for this article.

In the randomized, double-blind, placebo-controlled study by Allen and Bradley, 40 adults without disease received 500 mg of oral GSH or placebo twice daily for 4 weeks; 39 people completed the study per protocol. Changes in urinary F2-isoprostane (0.0 ± 0.1 and 0.0 ± 0.1; p = 0.38) and 8-OHdG (−0.2 ± 3.3 and 1.0 ± 3.2; p = 0.27) were not significant between groups; total reduced GSH, oxidized GSH, and their ratios also did not change. The authors concluded that oral glutathione supplementation in healthy adults did not produce significant changes in glutathione status, including oxidative stress markers. ^[2]

Because the two studies measured at different durations and in different samples (6 months and 4 weeks; blood cells and urinary markers), they do not directly refute each other; however, the results are not consistent regarding oral glutathione raising blood levels.

Are liposomal and sublingual glutathione forms different?

In the 1-month pilot study by Sinha and colleagues, 500 and 1,000 mg of liposomal GSH per day were used in healthy adults; GSH was measured in whole blood, erythrocytes, plasma, and peripheral blood mononuclear cells in 12 people. An increase was seen from the first week; at the second week, increases of up to 40% in whole blood, 25% in erythrocytes, 28% in plasma, and 100% in mononuclear cells were reported. The authors stated that no difference was seen between the two dose groups but that statistical power was limited because of the small sample. ^[3] The study was conducted with research funding from a dietary supplement company that supplies the liposomal glutathione product; the authors reported that the company had no role in design, data collection, analysis, or publication decisions and that there was no personal financial relationship for themselves. ^[3]

In the three-week crossover study by Schmitt and colleagues, 20 volunteers with metabolic syndrome compared N-acetylcysteine, oral GSH, and a new sublingual GSH form. In the sublingual group, an increase in plasma total and reduced GSH levels and a higher GSH/GSSG ratio (p = 0.003) were seen compared with the oral GSH group; plasma vitamin E level increased significantly only in the sublingual group. ^[4] A commercial laboratory is among the author addresses; the conflict-of-interest field in the PubMed record appears as “None.” These small studies measure blood levels; they do not measure health outcomes, and independent comparisons are needed for any inference of superiority between products.

Does glutathione affect oxidative stress and immunity?

For oxidative stress, results are mixed: in the 4-week study by Allen and Bradley, urinary F2-isoprostane and 8-OHdG markers did not change (above). ^[2] In the study by Richie and colleagues, however, the oxidized/reduced GSH ratio in whole blood decreased at month 6; this is a different marker. In a subgroup of the same study, immune markers were measured as a secondary outcome: in the high-dose group, natural killer (NK) cell cytotoxicity at month 3 increased more than twofold compared with placebo (p < 0.05). ^[1] This is an exploratory subgroup analysis, and the increase in NK cell activity is not an infection or disease outcome. In the pilot study by Sinha and colleagues, increased NK cytotoxicity and lymphocyte proliferation were also reported; the sample is 12 people and the study is company-funded. ^[3] The effect of glutathione on disease prevention or longevity was not measured in these studies.

Does glutathione lighten the skin?

The systematic review by Dilokthornsakul and colleagues found four studies examining skin effects of glutathione in healthy volunteers: three were placebo-controlled RCTs and one was a single-arm study; one used a topical form and the others used 250–500 mg/day oral forms. Oral glutathione at 500 mg/day and 2% topical oxidized glutathione lightened skin color in sun-exposed areas as measured by melanin index; in sun-protected areas, there was no significant difference in melanin index decrease with any product. Glutathione showed a trend toward improvement in wrinkles, elasticity, and UV spots; some non-serious side effects were reported. The authors described the evidence as “inconclusive” because of the quality of the studies and inconsistent findings. ^[5]

The 2025 systematic review by Sarkar and colleagues reported that, across five RCTs and a single-arm study, oral glutathione at 250 mg once daily, 250 mg twice daily, and 500 mg once daily significantly reduced melanin index compared with placebo; the risk-of-bias assessment showed low risk of bias in about half of the studies and high risk in half. The review states that the effect of the oral form spreads generally, while the topical form remains local, and that side effects are minimal with the topical form and marked with the oral form, and that effects are not sustainable with either form. ^[6] In the 12-week double-blind, placebo-controlled study by Weschawalit and colleagues, healthy women received 250 mg per day of reduced (GSH) or oxidized (GSSG) glutathione or placebo; melanin index and UV spots “tended” to be lower in the glutathione groups than with placebo, a significant decrease in wrinkles was seen in the GSH group in some regions, and no serious side effects were reported. ^[7] Because of subgroups, “tendency” statements, and the small size of the studies, the result is not strong (grade C).

Is intravenous glutathione safe?

Sonthalia and colleagues write that intravenous glutathione injections are popular but that no evidence proves their efficacy, and that the side effects caused by intravenous glutathione led the Philippine Food and Drug Administration (FDA) to issue a public warning condemning its use for off-label indications such as skin lightening. ^[8] In the review by Sarkar and colleagues, there is a single placebo-controlled study for intravenous administration (6 versus 3 people in a group of 16; p = 0.054); the authors say that intravenous use is contraindicated because of lack of efficacy and side effects. ^[6]

The Philippine FDA’s Advisory No. 2019-182 warns the public about the dangers associated with injectable skin-lightening agents such as glutathione and states that it has not approved any injectable product for skin lightening. ^[10] According to the US FDA’s announcement of August 27, 2026, adverse events were reported in at least 30 patients after intravenous administration of glutathione alone or with other components; the glutathione was prepared by different compounding pharmacies from a raw material labeled “supplement grade” that is not suitable for making injectable drugs. Two pharmacies recalled products because of high endotoxin levels in their glutathione injectables. The reported events were fever, chills, pain, dizziness, shock, and sepsis-like symptoms, some of which resulted in hospitalization; these symptoms are consistent with excessive endotoxin exposure. The FDA stated that it is investigating the events. ^[9] These documents belong to regulators in the United States and the Philippines.

What are the side effects of oral glutathione?

Some non-serious side effects were reported in the review by Dilokthornsakul and colleagues. ^[5] In the 12-week study by Weschawalit and colleagues, there were no serious side effects and the authors concluded that the two glutathione forms were well tolerated. ^[7] These data are at the level of weeks to months and were obtained mostly in healthy adults; pregnancy, breastfeeding, chronic disease, and drug interactions were not measured in these studies.

What is the regulatory status in Türkiye?

In Türkiye, glutathione falls under the Ministry of Agriculture and Forestry’s food supplement legislation. In the September 21, 2026 version of the Ministry’s Restricted Substances List for Food Supplements, chemical synthesis is stated as the source for “Glutathione”; the upper limit in the ages 11 and over column is 500 mg/day, with a publication date of March 8, 2016. ^[11] Oral doses between 250 and 1,000 mg/day were used in the studies; the list limit is the daily intake limit in the regulatory document, and comparison with study doses is not a recommendation. Intravenous administration is not a supplement; the above statements by US and Philippine regulators concern injectable use. This guide does not recommend products or places of purchase.

Evidence table: claim, population, and limits

This guide does not recommend individual doses; the figures above are reports of study and official document content.