Glutathione

Glutathione is the body's primary antioxidant, made naturally in nearly every cell to protect against oxidative stress and support detoxification; different forms are used for general antioxidant support, with its strongest clinical evidence in Parkinson's disease and emerging evidence for fatty liver disease. It's technically a tripeptide (built from three amino acids) with an unusual chemical structure that makes it unusually stable, not a typical peptide, and it's included in this library because it's often used alongside peptide protocols. It is not FDA-approved as a drug; it's sold as oral and liposomal supplements, and IV and inhaled forms are used in clinical and wellness settings.

Glutathione, the body's main antioxidant, has been studied across several uses, and how well it works depends heavily on route. Oral free glutathione is poorly absorbed, while liposomal oral forms have been shown in clinical work to raise the body's glutathione stores. IV glutathione has its strongest evidence in Parkinson's disease (a meta-analysis of randomized trials reported modest motor-score improvement) and emerging evidence in fatty-liver disease; other uses lack randomized-trial support, and evidence should not be transferred across different conditions.

Glutathione is not FDA approved as a pharmaceutical drug for any specific indication, though the compound is widely available in multiple regulatory categories: oral GSH (dietary supplement), liposomal oral GSH (dietary supplement), inhaled GSH (research/clinical use, particularly in cystic fibrosis), IV GSH (compounded by 503A pharmacies; widely offered at wellness clinics in the US and other jurisdictions; off-label clinical use in Parkinson's disease and other conditions). Glutathione is a tripeptide formed from the amino acids glutamate, cysteine, and glycine — endogenous to all human cells where it serves as the primary intracellular antioxidant. Injectable/IV glutathione for skin whitening is specifically flagged as unapproved and unsafe by the US FDA and the Philippine FDA (Advisory No. 2019-182). Not listed in the WADA 2026 Prohibited List.

Glutathione is not FDA-approved as a drug for any specific indication; oral forms are supplements and IV forms are compounded. It is not listed on the WADA Prohibited List. One use is specifically warned against by regulators: the US FDA and the Philippine FDA (Advisory No. 2019-182) have issued safety advisories against injectable or IV glutathione for skin whitening — an unapproved use, with reported risks including anaphylaxis and liver toxicity. VialWise is a research and educational reference, not medical advice — consult a licensed professional.

⚠️ For research and educational purposes only. Glutathione (GSH) is not approved by the FDA as a pharmaceutical drug for any specific indication. Information in this entry is informational, not medical advice. IV GSH administration through wellness clinics is widespread but operates in a regulatory gray area; researchers and clinicians should be aware of the regulatory context.

⚠️ Endogenous tripeptide — supplementation modulates levels of a natively-expressed compound. Glutathione is the primary intracellular antioxidant in essentially every human cell, present at intracellular concentrations of 1–10 mM. The compound is endogenous, synthesized from glutamate, cysteine, and glycine via two ATP-dependent enzymatic steps (γ-glutamylcysteine synthetase and glutathione synthetase). The supplementation rationale is restoration of GSH levels under conditions where endogenous synthesis is insufficient — oxidative stress, aging, certain disease states, intensive physical activity. As with NAD+, supplementation is modulating a natively-expressed compound rather than introducing a foreign biological.

⚠️ Bioavailability differs substantially by route — oral free GSH is poorly absorbed. Glutathione's bioavailability depends critically on the administration route: oral free GSH is largely degraded in the gastrointestinal tract before reaching systemic circulation; liposomal or sublingual oral GSH has improved bioavailability and produces measurable elevation of body GSH stores;[¹] IV GSH delivers GSH directly to circulation but the compound has a short plasma half-life;[²] inhaled GSH (used in cystic fibrosis research-community contexts) delivers GSH directly to lung tissue with limited systemic exposure. Researchers should select the route based on the published evidence supporting that specific route — oral free GSH supplementation is the most common and the most-poorly-supported by bioavailability evidence.

⚠️ Mechanism — primary intracellular antioxidant and detoxification cofactor. GSH acts via several mechanisms: (1) direct antioxidant — donates electrons to neutralize reactive oxygen species (ROS), oxidized to GSSG (glutathione disulfide); (2) substrate for glutathione peroxidase — reduces hydrogen peroxide and lipid peroxides; (3) glutathione S-transferase substrate — conjugates electrophilic xenobiotics (drugs, environmental toxins) for renal/biliary excretion; (4) regulator of redox-sensitive signaling — the GSH/GSSG ratio modulates activity of redox-sensitive enzymes and transcription factors (NF-κB, Nrf2, AP-1). The breadth of GSH's intracellular roles is the mechanistic basis for the wide range of clinical conditions where GSH supplementation has been studied.

⚠️ The IV GSH evidence base is mixed — some indications show real effects, others don't. IV GSH has been studied in multiple clinical contexts with varying levels of supporting evidence: Parkinson's disease has the strongest evidence base — a 2020 meta-analysis of 7 RCTs in 450 participants reported a statistically significant but mild improvement in updrs-III motor scores (SMD −0.48, P=0.02) without an increase in adverse events;[⁵] a separate Phase-I MR-spectroscopy study (n=15) demonstrated that intranasal GSH raises brain GSH levels, establishing CNS uptake;[³] non-alcoholic fatty liver disease has emerging evidence;[²] other indications (general anti-aging, skin lightening, chronic fatigue, autism) have research-community use without RCT-grade support. Injectable/IV GSH for skin whitening is an unapproved use that the US FDA and the Philippine FDA have issued safety warnings against.[⁶][⁷] Researchers should not transfer evidence across indications.

Glutathione (GSH) is an endogenous tripeptide (γ-glutamylcysteinylglycine) present at high intracellular concentrations (1–10 mM) in virtually all human cells. The compound is the primary intracellular antioxidant and a central player in cellular detoxification, redox signaling, and protein function. The structural distinction worth flagging: GSH is built with a γ-glutamate linkage rather than the canonical α-glutamate peptide bond, which protects the compound from typical cytoplasmic peptidase degradation and contributes to its high cytoplasmic stability. Synthesis is via two ATP-dependent enzymatic steps; the rate-limiting step is γ-glutamylcysteine synthetase (GCL), regulated by feedback inhibition from GSH and by Nrf2-mediated transcriptional upregulation under oxidative stress.

Mechanism — multiple intersecting roles. GSH's broad cellular roles include: - Direct antioxidant. GSH donates electrons to neutralize reactive oxygen species, becoming oxidized to glutathione disulfide (GSSG). The intracellular GSH/GSSG ratio is one of the most-tracked indicators of cellular redox state. - Glutathione peroxidase substrate. Glutathione peroxidase enzymes use GSH to reduce hydrogen peroxide and lipid peroxides to water and corresponding alcohols, protecting membranes and cytoplasmic proteins from oxidative damage. - Glutathione S-transferase substrate. GST enzymes conjugate GSH to electrophilic xenobiotics (drugs, toxins, environmental electrophiles), facilitating their solubilization and excretion via the renal and biliary routes. This is a load-bearing role in drug metabolism (acetaminophen detoxification is the classic textbook example). - Redox-sensitive signaling regulator. The GSH/GSSG ratio modulates activity of redox-sensitive transcription factors (NF-κB, Nrf2, AP-1) and enzymes (protein tyrosine phosphatases, redox-sensitive kinases). Cellular GSH status thus influences inflammatory signaling, stress responses, and cell-cycle regulation. - Protein S-glutathionylation. GSH can form mixed disulfide bonds with protein cysteines, modifying protein function in a redox-sensitive manner — a regulatory mechanism analogous to phosphorylation.

Common research / clinical interests. GSH supplementation use spans: - Parkinson's disease — GSH has the strongest clinical evidence base of any GSH supplementation indication. A 2020 meta-analysis pooling 7 RCTs (450 participants, mostly IV/IM routes) reported a statistically significant but mild improvement in updrs-III motor scores (SMD −0.48, 95% CI −0.88 to −0.08, P=0.02), with no increase in adverse events; the authors characterize the effect as mild.[⁵] A separate Phase-I MR-spectroscopy study (n=15) showed that intranasally administered GSH elevates brain GSH levels, establishing CNS uptake.[³] - Non-alcoholic fatty liver disease (NAFLD) — emerging evidence for GSH supplementation in NAFLD with favorable hepatic effects.[²] - Cystic fibrosis — inhaled (nebulized) GSH for airway oxidative stress; research/clinical use particularly outside the FDA-approved CF therapy framework. - General anti-aging / longevity protocols — research-community use as a general antioxidant; mechanistic rationale based on age-related decline in GSH levels. - Detoxification / chronic toxicity exposure — research-community use for heavy metal exposure, environmental toxin exposure, post-chemotherapy support. Evidence base is observational/case-series rather than RCT. - Skin lightening / cosmetic — research-community and clinical use (particularly in some Asian markets) for skin lightening, mediated through GSH's proposed interference with melanogenesis. ⚠️ Regulatory safety warning — injectable/IV GSH for skin whitening. The US FDA reports that no injectable glutathione product is approved for skin lightening and that no published clinical trials evaluate injectable GSH for this use; a 2019 FDA report documented adverse reactions (nausea, vomiting, chills, body aches) in patients given a compounded L-glutathione injectable. The Philippine FDA (FDA Advisory No. 2019-182, *"Unsafe use of glutathione as skin lightening agent,"* reinforced by the Department of Health in January 2024 against IV "gluta drips") warns of hepatotoxicity, severe allergic reactions including anaphylaxis, thyroid/renal/nervous-system toxicity, and Stevens-Johnson Syndrome / toxic epidermal necrolysis, and notes the absence of standardized dosing; injectable GSH is approved in the Philippines only as an adjunct in cisplatin chemotherapy, not for whitening. A 2025 narrative review reports that IV glutathione is associated with serious safety concerns including anaphylaxis and hepatotoxicity and lacks standardized dosing protocols,[⁶] and a 2024 systematic review concludes that IV glutathione is contraindicated for this use on the grounds of lack of demonstrated efficacy and side effects.[⁷] Topical and oral cosmetic preparations are regulated as cosmetics/supplements rather than pharmaceuticals; the injectable route is the one carrying the advisories. - Stack with peptides for oxidative-stress-management — common in research-community recovery and longevity protocols.

Regulatory status. Glutathione itself is not FDA-approved as a pharmaceutical drug. Oral GSH and liposomal GSH are sold as dietary supplements under DSHEA. IV GSH is offered at wellness clinics in the US through 503A compounding; regulatory enforcement varies. Inhaled GSH for cystic fibrosis is not FDA-approved but is used in research and some clinical contexts. Injectable/IV GSH for skin whitening is specifically unapproved and is the subject of safety advisories from the US FDA and the Philippine FDA (Advisory No. 2019-182) — see the skin-lightening bullet above. Glutathione is not listed in the WADA 2026 Prohibited List.

Commonly reported

• Active chemotherapy — interaction with chemotherapy detoxification is complex; consult oncologist.
• Active asthma (for inhaled use) — caution.
• Long-term safety of supraphysiologic GSH supplementation — incompletely characterized but no clear pattern of adverse effects.

Active chemotherapy without oncologist consultation — caution

Active asthma (for inhaled use) — caution

Pregnancy and lactation — limited data; default to caution

Pediatric use — limited data outside specific clinical contexts (CF inhaled use in pediatric patients)

Known sulfur sensitivity — rare; potential for sulfur-related side effects

Injectable / IV GSH for skin whitening — not an approved use; regulators advise against it. The US FDA reports no approved injectable GSH for skin lightening and no published clinical trials supporting it; the Philippine FDA (Advisory No. 2019-182) warns of hepatotoxicity, anaphylaxis, thyroid/renal/nervous-system toxicity, and Stevens-Johnson Syndrome / toxic epidermal necrolysis. Peer-reviewed reviews reach the same conclusion.[⁶][⁷]

Regulatory note (US): Oral GSH is a dietary supplement. IV GSH is compounded; no FDA approval for any specific indication, and injectable GSH for skin lightening is specifically unapproved.

Regulatory note (WADA): GSH is not listed in the 2026 WADA Prohibited List.

Tripeptide

A peptide made of exactly three amino acids.

Endogenous

Naturally produced by the body, rather than introduced from outside.

Antioxidant

A molecule that neutralizes reactive oxygen species (free radicals) to protect cells from oxidative damage.

Half-life

Roughly how long the body takes to clear half of a dose. A long half-life is why some compounds can be taken only once a week.

Investigational

Still being studied and not yet approved by regulators for general use.

1. Sinha R, Sinha I, Calcagnotto A, Trushin N, Haley JS, Schell TD, Richie JP Jr. (2018). Oral supplementation with liposomal glutathione elevates body stores of glutathione and markers of immune function. European Journal of Clinical Nutrition, 72(1):105-111. doi: 10.1038/ejcn.2017.132.(PMID 28853742)
2. Santacroce G, Gentile A, Soriano S, Novelli A, Lenti MV, Di Sabatino A. (2023). Glutathione: Pharmacological aspects and implications for clinical use in non-alcoholic fatty liver disease. Frontiers in Medicine, 10:1124275. doi: 10.3389/fmed.2023.1124275.(PMID 37035339)
3. Mischley LK, Conley KE, Shankland EG, Kavanagh TJ, Rosenfeld ME, Duda JE, White CC, Wilbur TK, De La Torre PU, Padowski JM. (2016). Central nervous system uptake of intranasal glutathione in Parkinson's disease. NPJ Parkinson's Disease, 2:16002. doi: 10.1038/npjparkd.2016.2.(PMID 28725693)
4. World Anti-Doping Agency. The 2026 Prohibited List, International Standard (effective 1 January 2026). Glutathione is not listed in the 2026 WADA Prohibited List.
5. Wang HL, Zhang J, Li YP, Dong L, Chen YZ. (2020). Potential use of glutathione as a treatment for Parkinson's disease. Experimental and Therapeutic Medicine, 21(2):125. doi: 10.3892/etm.2020.9557.(PMID 33376507)
6. Alzahrani TF, et al. (2025). Exploring the Safety and Efficacy of Glutathione Supplementation for Skin Lightening: A Narrative Review. Cureus, 17(1):e78045. doi: 10.7759/cureus.78045.(PMID 40013212)
7. Sarkar R, et al. (2024). Glutathione as a skin-lightening agent and in melasma: a systematic review. International Journal of Dermatology, 64(6):992-1004. doi: 10.1111/ijd.17535.(PMID 39444151)
8. Regulatory safety advisories — injectable/IV glutathione for skin whitening. US FDA: no injectable glutathione product is approved for skin lightening; the FDA has stated that no published clinical trials evaluate injectable GSH for this use, and a 2019 report documented adverse reactions (nausea, vomiting, chills, body aches) in patients given a compounded L-glutathione injectable. Philippine FDA: FDA Advisory No. 2019-182, "Unsafe use of glutathione as skin lightening agent" (fda.gov.ph), reinforced in January 2024 by DOH Secretary Herbosa warning against IV "gluta drips"; cited risks include hepatotoxicity, severe allergic reactions/anaphylaxis, thyroid/renal/nervous-system toxicity, and Stevens-Johnson Syndrome / toxic epidermal necrolysis, with no standardized dosing. Injectable GSH is approved in the Philippines only as an adjunct in cisplatin chemotherapy, not for whitening.

• NAD+ — same mechanism class
• Cerebrolysin — shared research area
• Humanin — shared research area
• MGF — shared research area
• Oxytocin — shared research area
• P021 — shared research area