Glutathione

Glutathione (GSH) is a three-amino-acid molecule and the main low-molecular-weight antioxidant inside cells, kept at millimolar concentrations in tissues ¹. It works as part of a cycle: the cell uses it to neutralize reactive oxygen species, then recycles the oxidized form back to active GSH with the enzyme glutathione reductase ¹.

Research has tested it across several delivery routes. A randomized placebo-controlled trial gave intravenous GSH alongside oxaliplatin chemotherapy and found less treatment-related neurotoxicity ⁵. A crossover trial found sublingual GSH raised plasma GSH and the ratio of reduced to oxidized GSH better than oral GSH or N-acetylcysteine ⁶. Three months of oral liposomal GSH reduced oxidative stress and supported immune function in adults with type 2 diabetes ⁷. GSH levels also decline with age, while unusually high GSH appears in older adults in excellent health, which underlies interest in it for healthspan ¹.

Glutathione's core job is electron donation. It gives electrons to neutralize harmful oxidants such as hydrogen peroxide, turning into its oxidized partner glutathione disulfide (GSSG). An enzyme called glutathione reductase then recycles GSSG back to active GSH, so the cell usually keeps the pool mostly reduced ¹.

Main pathways

• Peroxide detoxification: Selenium-containing enzymes called glutathione peroxidases use GSH to convert hydrogen peroxide and lipid peroxides into water or alcohols. One form, GPX4, protects cell membranes and is a checkpoint that prevents iron-dependent cell death known as ferroptosis ¹¹.
• Detoxification and conjugation: Glutathione S-transferases attach GSH to reactive chemicals so they can be excreted. This is the route that clears a toxic metabolite of acetaminophen ¹⁴.
• Mitochondrial pool: Mitochondria maintain a separate GSH supply through the SLC25A39 transporter. When mitochondrial levels fall, the cell stabilizes this transporter to import more, an autoregulatory loop tied to iron status ³.

Human trials are small but show measurable route-specific effects.

• Neuropathy protection: In a randomized, double-blind, placebo-controlled trial, intravenous GSH given before oxaliplatin reduced chemotherapy-induced neurotoxicity without lowering antitumor activity in advanced colorectal cancer ⁵.
• Blood redox markers: A 3-week crossover in 20 adults with metabolic syndrome found sublingual GSH raised total and reduced plasma GSH and the GSH/GSSG ratio more than oral GSH or NAC; only sublingual GSH also raised plasma vitamin E ⁶.
• Immune and oxidative support in diabetes: Three months of oral liposomal GSH prevented GSH depletion, reduced oxidative stress, increased Th1 cytokines, and lowered IL-6 in adults with type 2 diabetes ⁷.
• Cystic fibrosis: A small pilot tested inhaled buffered GSH for lung disease; efficacy is not established by randomized evidence ⁸.

Preclinical findings are stronger on mechanism than on human outcomes. In aged mice, raising GSH with N-acetylcysteine restored a form of hippocampal synaptic plasticity, a marker of learning-related brain function ⁹. In Parkinson's disease, affected brain regions show lower GSH and GSH/GSSG, though cause and effect remain unresolved ¹⁰. In canine semen, 10 mM GSH improved cryopreservation, while 20 mM worsened oxidative damage, suggesting the useful range is narrow ²⁷.

Published protocols vary by route and goal.

Protocol	Route	Reported dose	Duration
Neuroprotection during oxaliplatin	IV	1.5 g/m² before each cycle	Throughout chemotherapy 5
Redox repletion in metabolic syndrome	Sublingual	Trial-comparator dosing; raised plasma GSH and GSH/GSSG	3 weeks 6
Immune/oxidative support in type 2 diabetes	Oral liposomal	Daily trial dosing; prevented depletion	3 months 7
Nitric-oxide support with L-citrulline	Oral	GSH 200 mg/day with 2 g citrulline	7 days 29

For injectable use outside oncology, practitioner protocols commonly use 600-1400 mg intravenously one to three times weekly, or 600-1200 mg intramuscularly one to two times weekly, typically for 8-12 weeks. Body-weight-scaled oral ranges appear in published human data at roughly 2-20 mg/kg/day ⁶. Community practice often runs courses with a rest period, but no withdrawal or rebound effects are documented ⁵.

Injectable glutathione is supplied as a sterile lyophilized powder, commonly in 600 mg, 1200 mg, or 2000 mg clinical vials. It is reconstituted with sterile water for injection or bacteriostatic water; normal saline can be used for further intravenous dilution, as in the oxaliplatin neuroprotection trial where the dose was prepared immediately before infusion ⁵.

Handling matters because reduced glutathione oxidizes spontaneously in solution. Dissolve it by gentle swirling, and avoid vigorous agitation, which speeds oxidation. Use water-based diluents only; alkaline buffers and metal-containing solutions promote degradation.

For storage, keep lyophilized powder refrigerated at 2-8°C for routine use, or frozen and protected from light for long-term storage. Once reconstituted, refrigerate the solution. Single-use clinical vials should be used within 24 hours; multi-use research vials in bacteriostatic water may remain acceptable up to 7 days refrigerated. Do not freeze reconstituted glutathione. Discard any solution that looks yellow, cloudy, or contains particles.

The calculator below handles the dilution math for standard vial sizes and a chosen research dose.

Glutathione participates in drug metabolism, so the strongest interaction data involve chemotherapy.

• Platinum drugs (cisplatin, carboplatin, oxaliplatin): Tumor cells use GSH to detoxify these agents; intracellular GSH correlates with resistance in ovarian cancer cell lines ³⁷. At the same time, an RCT found GSH with oxaliplatin reduced neurotoxicity without undermining antitumor effect ⁵. Use during chemotherapy belongs under oncologist supervision.
• Alkylating agents: Busulfan elimination consumes GSH, and pre-dose blood GSH predicted busulfan clearance in transplant patients ⁴⁶.
• Acetaminophen: A reactive acetaminophen metabolite is cleared by GSH conjugation ¹⁴, and the acetaminophen-GSH conjugate can inhibit glutathione reductase, adding oxidative burden beyond GSH depletion ³⁴.
• Topoisomerase poisons: In cell studies, GSH depletion did not potentiate doxorubicin or etoposide toxicity, a narrower interaction than with platinums and alkylators ⁴⁴.
• Sulfasalazine: This drug blocks cystine uptake and depletes GSH to sensitize tumors to radiation; supplemental GSH may partially oppose that mechanism ⁴⁷.

Among supplements, sublingual GSH outperformed NAC for raising plasma GSH in a crossover trial ⁶. Combined L-citrulline plus GSH increased post-exercise nitric-oxide markers ²⁹. Selenium supports GPX4 function ¹¹, and the immediate precursor GGC restored glutathione in stressed human astrocytes ²⁵.

Controlled trials of glutathione combined with other injectable peptides do not exist, but the literature points to several complementary pairings.

• Vitamin C: Ascorbate and GSH recycle each other's oxidized forms, so they are often combined in intravenous antioxidant practice. The combination is based on redox biochemistry rather than an RCT ²³.
• L-citrulline: A small human trial found GSH plus citrulline increased nitric-oxide markers after resistance exercise ²⁹.
• NAC or GGC: These are precursors rather than stack partners. GGC bypasses the rate-limiting step in GSH synthesis and restored GSH in stressed astrocytes ²⁵, while gamma-glutamylcysteine reduced inflammation in a sepsis model ²⁴.
• Alpha-lipoic acid: Its reduced form DHLA directly reduces oxidized phospholipids, complementing the GSH-dependent arm of ferroptosis defense ¹⁹.
• Mitochondrial peptides: Mitochondria-targeting peptides such as MOTS-c or SS-31 are theoretically additive because mitochondrial GSH independently governs survival under oxidative load ¹⁹. No human combination data exist.

Anything containing iron or copper should be kept separate from injectable GSH, because GSH-metal complexes can cycle redox-active metals ³³.

Glutathione holds no FDA drug approval for any indication. It is lawful as an oral dietary supplement and food ingredient in the US, but injectable forms marketed for wellness, detox, or skin lightening are treated by FDA as unapproved drugs, and warning letters have targeted clinics and compounding pharmacies. A 503A pharmacy may compound injectable GSH for an individual patient-specific prescription, but wholesale manufacture for office IV-drip menus falls outside that protection.

The clinical literature gives a reason for injectable interest: an intravenous dose reduced chemotherapy-induced neuropathy in a randomized controlled trial ⁵. Oral forms have stronger regulatory footing but lower bioavailability, and a crossover trial found sublingual GSH raised plasma GSH more than plain oral GSH or NAC ⁶. In the EU, there is no centralized marketing authorization; national compounding and food-supplement law govern availability. The UK treats injectable GSH as an unlicensed medicine, Australia has not registered it and has acted against IV promotion, and some Southeast Asian regulators have registered parenteral products.

For athletes, GSH is not on the WADA Prohibited List. The practical limit is WADA rule M2.2: most commercial IV drips exceed the permitted infusion volume and are prohibited without a therapeutic use exemption. Oral and sublingual forms avoid that issue.

Across the randomized and placebo-controlled trials, glutathione was well tolerated, with no serious adverse events or discontinuations attributed to it ⁵.

• Gastrointestinal: Plain oral GSH can cause dose-dependent bloating, sulfurous belching, flatulence, and loose stools, because much of the swallowed dose is degraded in the gut. Sublingual and liposomal forms reduce but do not eliminate these effects ⁶.
• Infusion reactions: Intravenous GSH may cause transient flushing, nausea, or lightheadedness early in the infusion; slowing the rate usually resolves this.
• Inhaled route: Airway irritation and bronchospasm are reported with inhaled GSH, especially where airway conditions exist. Buffered formulations are preferred in the cystic fibrosis pilot ⁸.
• Metal-related pro-oxidant effects: In the presence of copper, GSH complexes can generate superoxide, which matters in copper overload states ³³. Large redox shifts can also move zinc between binding proteins and enzymes ³⁵.
• Dose ceiling: In canine sperm studies, 10 mM GSH protected sperm, but 20 mM increased oxidative damage, implying that supraphysiological concentrations are not protective ²⁷.

The main theoretical concern is cancer: tumors upregulate GSH synthesis and use glutathione-dependent enzymes for drug resistance ¹³. Intracellular GSH correlates strongly with platinum resistance in cancer cell lines ³⁷. The oxaliplatin RCT found no loss of antitumor efficacy, but high-dose supplementation during active malignancy remains a risk not resolved by human outcome data ⁵.