Glutathione

What it is

Glutathione is a naturally occurring intracellular antioxidant and redox-buffering molecule present in human cells. It is commonly abbreviated GSH when referring to the reduced form and GSSG when referring to the oxidized disulfide form^{[1 ,6 ]}. Unlike many peptides marketed through wellness clinics, glutathione is not a novel research peptide; it is an endogenous tripeptide central to cellular detoxification, peroxide reduction, thiol-disulfide balance, and conjugation reactions^{[6 –7 ]}.

Chemical structure and biology

Glutathione is L-gamma-glutamyl-L-cysteinylglycine, a tripeptide containing glutamate, cysteine, and glycine with a reactive sulfhydryl group on cysteine. FDA’s Substance Registration System lists glutathione under UNII GAN16C9B8O and notes that UNII availability does not imply regulatory approval^{[1 ]}.

The molecule is synthesized inside cells from glutamate, cysteine, and glycine. Its cysteine sulfhydryl group allows it to participate in redox reactions and to serve as a substrate for enzymes such as glutathione peroxidases and glutathione S-transferases^{[6 –7 ]}. In plain terms, glutathione helps maintain the intracellular chemical environment in which proteins, membranes, mitochondria, and detoxification pathways can function normally. Low glutathione status is associated with oxidative-stress biology in several diseases, but association does not prove that glutathione administration treats those diseases^{[6 –9 ]}.

Formulations

Clinically discussed formulations include oral capsules, liposomal oral preparations, sublingual products, topical cosmetic products, nebulized or inhaled formulations in research, intranasal formulations in Parkinson disease research, and compounded intravenous formulations used by some clinics^{[8 –17 ]}. These routes are not interchangeable. Oral glutathione studies mainly assess whether supplementation changes blood or cellular glutathione stores^{[10 –13 ]}. Intranasal studies in Parkinson disease have focused on safety, tolerability, and exploratory symptom outcomes^{[8 –9 ]}. Inhaled studies in cystic fibrosis evaluate pulmonary endpoints^{[14 –15 ]}. Cosmetic studies evaluate melanin index and related skin measures^{[16 –19 ]}.

The public wellness framing often uses broad terms such as “detox,” “anti-aging,” “immune support,” or “skin brightening.” The evidence base is narrower. Some human trials show changes in biomarkers or small cosmetic outcomes, while disease-treatment evidence remains limited, route-specific, and often preliminary^{[8 –19 ]}. FDA has also highlighted specific safety risks when a dietary ingredient grade of L-glutathione was used to compound sterile injectable drugs^{[5 ]}.

Regulatory status

No FDA-approved finished drug product containing glutathione as the active ingredient was identified in the United States sources reviewed for this draft. FDA’s Substance Registration System identifies glutathione chemically, but FDA states that UNII assignment does not imply regulatory review or approval^{[1 ]}. DrugBank lists glutathione as not US-approved while approved in other jurisdictions, but DrugBank is a secondary database and should not be treated as a US regulatory authority^{[20 ]}.

503A and 503B Category 1 interim status

Glutathione does appear in FDA’s bulk-substance compounding materials. FDA’s April 22, 2026 503A nomination PDF lists “Glutathione” in Category 1, meaning it is under evaluation and may be within FDA’s interim enforcement policy when all stated conditions are met^{[2 ,4 ]}. FDA’s March 21, 2025 503B nominated-substances PDF also lists “Glutathione” in 503B Category 1, meaning it has been nominated with sufficient supporting information for FDA to evaluate and does not appear on another disqualifying list^{[3 –4 ]}. Category 1 is not the same as FDA approval and is not the final 503A or 503B bulks list^{[2 –4 ]}.

Under FDA’s compounding framework, 503A pharmacies and physicians using bulk drug substances must satisfy the statutory conditions for 503A, including applicable monograph or approved-drug-component rules, or appearance on the 503A bulks list if other routes do not apply^{[4 ]}. FDA states that 503B outsourcing facilities may use a bulk substance only if it appears on the 503B bulks list or the compounded drug appears on FDA’s drug shortage list at the time of compounding, distribution, and dispensing^{[4 ]}. Because glutathione is currently in Category 1 rather than a final bulks-list entry, platform listings should be legally reviewed before publication.

2019 FDA compounding alert

FDA issued a specific compounding alert on June 7, 2019, after adverse events were reported in patients receiving compounded injectable L-glutathione made with dietary supplement-grade powder. FDA reported symptoms including nausea, vomiting, lightheadedness, chills, body aches, sneezing, hypotension, and difficulty breathing, and FDA testing found excessive bacterial endotoxin in samples^{[5 ]}. FDA concluded that the dietary-supplement-labeled L-glutathione powder “should not have been used” to compound sterile injectable drugs^{[5 ]}. This alert does not prohibit all compliant glutathione compounding, but it is central to the safety profile of injectable formulations.

Controlled-substance and international status

Glutathione is not listed in the federal controlled-substance schedules reviewed in 21 CFR Part 1308^{[21 ]}. Internationally, some jurisdictions have approved injectable glutathione for narrow medical contexts; for example, Philippine public-health communications describe approval as an adjunct treatment in cisplatin chemotherapy, while warning against injectable use for skin whitening^{[22 ]}. This page focuses on United States status. Date of last regulatory verification: May 5, 2026.

Research summary

Oral bioavailability

The most basic clinical question is whether oral glutathione changes body glutathione stores. Richie and colleagues conducted a six-month randomized, double-blind, placebo-controlled trial of oral glutathione in 54 nonsmoking adults, testing 250 mg/day and 1,000 mg/day^{[10 ]}. The study reported increases in blood, erythrocyte, plasma, lymphocyte, and buccal-cell glutathione stores, especially in the higher-dose group, with levels returning toward baseline after washout^{[10 ]}. A smaller pilot study of liposomal glutathione in 12 healthy adults reported increases in whole blood, erythrocyte, plasma, and peripheral blood mononuclear cell glutathione and reductions in selected oxidative-stress biomarkers after short-term supplementation^{[11 ]}. These studies support bioavailability and biomarker effects, not disease-treatment claims.

Other oral studies are more mixed. Allen and Bradley conducted a randomized, double-blind, placebo-controlled trial of oral glutathione in 40 healthy adults and assessed urinary F2-isoprostanes and 8-hydroxy-2’-deoxyguanosine as oxidative-stress biomarkers^{[12 ]}. Schmitt and colleagues conducted a randomized crossover study comparing N-acetylcysteine, oral glutathione, and sublingual glutathione in 20 volunteers with metabolic syndrome, focusing on bioavailability and oxidative-stress markers^{[13 ]}. Taken together, oral research suggests that formulation, duration, population, and outcome selection matter. It does not establish oral glutathione as a treatment for “detoxification,” aging, immune deficiency, or chronic disease in otherwise unselected patients.

Parkinson disease

Parkinson disease has been a recurring research area because reduced glutathione depletion has been observed in the substantia nigra of people with Parkinson disease^{[23 ]}. A 2015 randomized, double-blind phase I/IIa study assigned 30 people with Parkinson disease to intranasal placebo, 300 mg/day, or 600 mg/day glutathione for three months and found no substantial safety or tolerability differences across groups^{[8 ]}. A later phase IIb trial randomized 45 people with Hoehn and Yahr stage 1–3 Parkinson disease to intranasal placebo, 100 mg, or 200 mg glutathione three times daily for three months^{[9 ]}. All groups improved, and although the high-dose group improved from baseline, neither active group was superior to placebo^{[9 ]}. A 2021 meta-analysis reported signals in UPDRS III and glutathione peroxidase across seven randomized trials, but the field remains limited by study heterogeneity, size, formulation differences, and trial quality^{[24 ]}.

Intravenous glutathione for Parkinson disease has less robust evidence than many public claims suggest. Sechi and colleagues reported an open-label study of reduced intravenous glutathione in early Parkinson disease in 1996, and Hauser and colleagues later published a randomized double-blind pilot evaluation of intravenous glutathione^{[25 –26 ]}. Case reports also exist^{[27 ]}. These studies are hypothesis-generating and do not establish IV glutathione as an FDA-approved or standard Parkinson disease therapy.

Cystic fibrosis

In cystic fibrosis, the rationale is local oxidative stress in airway epithelial lining fluid. Roum and colleagues reported that glutathione aerosol suppressed inflammatory-cell-derived oxidants in the lung epithelial surface of people with cystic fibrosis^{[15 ]}. A later randomized, single-blind, placebo-controlled trial by Calabrese and colleagues randomized 54 adults and 51 pediatric patients with cystic fibrosis to inhaled glutathione or placebo twice daily for 12 months^{[14 ]}. The trial did not meet its predetermined primary outcome of 15% FEV1 improvement, though subgroup and secondary signals were reported and treatment was well tolerated^{[14 ]}. This is not evidence for routine nebulized glutathione outside specialist pulmonary research or care.

NAFLD

Liver-related evidence is preliminary. Honda and colleagues conducted an open-label, single-arm, multicenter pilot study of oral glutathione in 34 patients with nonalcoholic fatty liver disease after a three-month lifestyle intervention; 29 completed the protocol^{[17 ]}. ALT decreased after four months of glutathione, and triglycerides, nonesterified fatty acids, and ferritin also decreased^{[17 ]}. Because the study lacked a placebo control and followed lifestyle intervention, it cannot establish efficacy for NAFLD. It supports further research, not a treatment recommendation.

Cosmetic skin lightening

Cosmetic skin-lightening research is limited and ethically sensitive. Arjinpathana and Asawanonda randomized 60 healthy medical students to oral glutathione or placebo for four weeks and reported statistically greater melanin-index reductions at two of six measured sites, with long-term safety not established^{[16 ]}. Watanabe and colleagues studied topical 2% oxidized glutathione lotion in 30 healthy women and found lower melanin index on treated facial sites than placebo-treated sites^{[18 ]}. A 2019 systematic review found only four clinical studies and concluded evidence was inconclusive due to study quality and inconsistent findings^{[19 ]}. Reviews of IV glutathione for skin lightening emphasize inadequate safety data and lack of published trials of IV use for that cosmetic purpose^{[28 –29 ]}.

Where the evidence ends

Overall, glutathione has strong biological plausibility as an endogenous redox compound and modest human data for changing biomarkers. It does not have robust evidence as a broad wellness, anti-aging, detox, Parkinson disease, NAFLD, cystic fibrosis, or injectable skin-lightening therapy. Evidence should be described by route and indication, with injectable claims treated especially cautiously.

Public discourse

Laurie K. Mischley, ND, PhD, Parkinson disease researcher, reported in her 2017 phase IIb intranasal glutathione study that the active arms improved from baseline but did not outperform placebo^{[9 ]}.

Seemal Desai, MD, dermatologist, raised concerns about unregulated IV glutathione used for skin lightening^{[30 ]}.

Ted Herbosa, MD, Philippine Secretary of Health, warned publicly against IV glutathione use for skin whitening after a reported clinic death^{[22 ]}.

Sidharth Sonthalia, MD, dermatologist and review author, summarized the gap between marketing and evidence for glutathione skin lightening^{[29 ]}.

Public discourse reflects the views of the speakers cited and does not represent medical advice or the editorial position of ProPeptideGuide.

Side effects and safety

The most serious documented US safety issue is compounded injectable product quality. FDA’s 2019 alert described adverse events after patients received IV L-glutathione compounded with dietary supplement-grade powder; symptoms included nausea, vomiting, lightheadedness, chills, body aches, sneezing, hypotension, and difficulty breathing, and one patient was transferred to a hospital^{[5 ]}. FDA testing found excessive bacterial endotoxin in multiple samples and emphasized that ingredients not intended for sterile injectable drugs may contain impurities and contaminants^{[5 ]}.

Injectable risks

General injectable risks include contamination, endotoxin exposure, incorrect concentration, pH or osmolality problems, nonsterile administration, infusion reactions, vein irritation, and hypersensitivity. These risks are distinct from the intrinsic biology of glutathione and arise from route, formulation, handling, and setting. They are especially relevant to wellness-clinic infusions and cosmetic skin-lightening drips.

Other route-specific signals

In intranasal Parkinson disease trials, glutathione was generally tolerable over three months, but one participant in the high-dose arm of the phase IIb trial developed cardiomyopathy^{[8 –9 ]}. The trial did not establish causality, but the event underscores why larger studies are needed before long-term neurologic use can be described as safe^{[9 ]}.

In inhaled cystic fibrosis research, glutathione was reported as well tolerated in the 12-month randomized trial, but the trial did not meet its primary lung-function endpoint^{[14 ]}. In oral and topical cosmetic trials, short-term tolerability was generally favorable, but long-term systemic or repeated injectable safety is not established^{[16 –19 ,28 –29 ]}.

No FDA-approved label

There is no FDA-approved US label for glutathione as a drug, so there is no FDA-reviewed contraindication, warning, pregnancy, lactation, or drug-interaction framework for a finished product. Theoretical cautions include use in oncology contexts without specialist oversight, because antioxidant interventions may interact conceptually with oxidative mechanisms of some cancer therapies; this should be evaluated by the treating oncology team rather than inferred from supplement marketing. Long-term safety data for repeated compounded IV glutathione used for wellness or skin lightening are inadequate.

Available through

Glutathione may be available through compliant US compounding channels when prescribed by a licensed clinician and prepared by a pharmacy or outsourcing facility operating within applicable 503A or 503B requirements^{[2 –5 ]}. Because glutathione is in FDA Category 1 interim lists rather than a final FDA-approved finished-product pathway, any provider listing should be reviewed for compounding compliance, sterile-drug quality controls, sourcing, route, claims, and state-law requirements.

Telehealth platform partnerships are pending verification. ProPeptideGuide does not link to or endorse gray-market vendors, research-chemical sellers, cosmetic IV drip clinics making noncompliant claims, or products marketed as FDA-approved glutathione treatments for wellness, detox, Parkinson disease, NAFLD, cystic fibrosis, or skin lightening.