Endogenous tripeptide and the body's master antioxidant. Very short plasma half-life with rapid cellular uptake. Parenteral route preferred due to poor oral bioavailability.
Glutathione (GSH) is an endogenous tripeptide composed of glutamic acid, cysteine, and glycine in a unique gamma-linkage (γ-glutamyl-cysteinyl-glycine). With a molecular weight of 307.3 Da, it is the most abundant intracellular antioxidant in the human body — present in virtually every cell at millimolar concentrations.
Glutathione serves as the primary substrate for the glutathione peroxidase (GPx) and glutathione S-transferase (GST) enzyme families, which together form the body's core detoxification and free radical neutralization system. Every cell maintains a pool of reduced glutathione (GSH) and oxidized glutathione (GSSG), and the GSH/GSSG ratio is one of the most important indicators of cellular oxidative stress.
The rationale for parenteral (injectable) glutathione stems from a fundamental bioavailability problem: oral glutathione is rapidly degraded by peptidases in the gastrointestinal tract and extensively metabolized during first-pass through the liver. Subcutaneous injection bypasses both barriers, delivering intact glutathione directly into systemic circulation. The 15-minute plasma half-life reflects not instability, but rapid cellular uptake — the body efficiently pulls circulating glutathione into cells where it is needed.
Glutathione operates across several interconnected biochemical pathways, all centered on its thiol (–SH) group on the cysteine residue, which serves as the active site for electron donation:
Glutathione directly neutralizes reactive oxygen species (ROS) and reactive nitrogen species (RNS) by donating an electron from its thiol group. In this reaction, two molecules of reduced GSH are oxidized to form GSSG (glutathione disulfide). The enzyme glutathione reductase then recycles GSSG back to GSH using NADPH as the electron donor — linking glutathione recycling directly to the NAD+/NADPH metabolic axis.
Glutathione S-transferase (GST) enzymes conjugate glutathione to xenobiotics, drugs, and endogenous waste products, making them water-soluble for excretion via bile or urine. This is Phase II of the hepatic detoxification pathway. Approximately 80% of the body's glutathione pool is concentrated in the liver, reflecting the organ's central role in detoxification.
Lymphocytes, macrophages, and other immune cells require adequate intracellular glutathione for optimal function. GSH depletion is associated with impaired immune cell proliferation and reduced cytokine signaling. Replenishing glutathione supports the metabolic demands of active immune responses.
Injectable glutathione has one of the shortest plasma half-lives of any compound tracked in Milligram. After subcutaneous administration, peak plasma levels are reached within approximately 15 minutes, and the plasma half-life is also approximately 15 minutes. This rapid clearance reflects efficient cellular uptake rather than degradation — glutathione is actively transported into cells by carrier proteins including OATP (organic anion transporting polypeptides).
| Parameter | Value |
|---|---|
| Plasma Half-Life | ~15 minutes |
| Time to Peak (Tmax) | ~15 minutes post-injection |
| Bioavailability (SubQ) | ~90% |
| Functional Duration | ~2 hours |
| Steady State | Not applicable (cleared between daily doses) |
| Primary Clearance | Cellular uptake via OATP transporters |
| Extracellular Degradation | γ-glutamyltransferase (GGT) on cell surfaces |
The 15-minute plasma half-life can appear alarming at first glance, but it is misleading if interpreted as "the compound stops working after 15 minutes." Glutathione's disappearance from plasma reflects active cellular uptake — the body is pulling the compound into cells where it becomes part of the intracellular GSH pool. Once inside cells, glutathione participates in redox cycling and is continuously recycled between GSH and GSSG forms. The functional benefit persists well beyond plasma clearance.
Inside cells, glutathione exists in a dynamic equilibrium between its reduced (GSH, active) and oxidized (GSSG, inactive) forms. The enzyme glutathione reductase continuously recycles GSSG back to GSH using NADPH as the reducing agent. A healthy cell maintains a GSH/GSSG ratio of approximately 100:1 to 500:1. When this ratio drops — due to oxidative stress, toxin exposure, or aging — cellular function is compromised. Exogenous glutathione supplementation replenishes the intracellular GSH pool, supporting the maintenance of optimal redox balance.
Glutathione dosing varies between subcutaneous self-administration and clinical IV push protocols. Commonly reported structures:
Glutathione and NAD+ are frequently administered together in longevity protocols because their mechanisms are biochemically linked. Glutathione recycling (GSSG → GSH) requires NADPH, which is derived from NAD+ metabolism. By replenishing both pools simultaneously, the two compounds support each other's functional pathways. Many IV clinics administer a glutathione push immediately following an NAD+ infusion.
Glutathione for SubQ injection is available as both pre-mixed sterile solutions and lyophilized powder. For lyophilized vials:
Glutathione lyophilized vial (commonly 200 mg or 600 mg), bacteriostatic water, alcohol swabs, and insulin syringes (29–31 gauge).
Swab both vial stoppers with alcohol pads. Allow to air dry for a few seconds before puncturing.
For a 600 mg vial, adding 2 mL BAC water yields a concentration of 300 mg/mL. For a 200 mg dose, draw 0.67 mL (approximately 67 units on an insulin syringe). Direct the stream down the glass wall.
Glutathione dissolves readily with gentle swirling. The solution should be clear and colorless to slightly pale yellow. Discard if visibly cloudy or if particulates are present.
Common injection sites include the abdomen (2 inches from the navel) and outer thigh. Rotate sites between injections to prevent localized irritation.
Refrigerate reconstituted glutathione at 2–8°C immediately after preparation. Protect from light. Use within 14–28 days depending on manufacturer guidance. Glutathione is sensitive to oxidation — minimize air exposure in the vial.