Glutathione: The Tripeptide Your Cells Already Make

Glutathione is a tripeptide — glutamate, cysteine, glycine — and unlike several compounds sold in this space, it genuinely is a peptide. It is also one your cells synthesise continuously, in quantity, as the body’s principal intracellular antioxidant.

That last point is what makes supplementing it more complicated than it first appears.

What it does

Glutathione neutralises reactive oxygen species and is central to detoxification pathways in the liver, where it conjugates compounds for excretion. It cycles between reduced (GSH) and oxidised (GSSG) forms, and the ratio between them is used as a marker of oxidative stress.

Levels decline with age and are lower in a range of disease states, which is the observation driving supplementation interest — the same pattern seen with NAD+ and GHK-Cu.

Why oral glutathione is a problem

A tripeptide taken orally meets the same machinery as any other peptide: it is broken into its constituent amino acids. What reaches your cells is glutamate, cysteine and glycine — not glutathione.

That is why the supplement market splits three ways:

• Oral glutathione. Largely digested; absorption of the intact tripeptide is limited.

• Liposomal glutathione. Encapsulated to survive digestion, with variable evidence.

• Precursors. N-acetylcysteine supplies the rate-limiting amino acid and lets the body make its own — mechanistically the most straightforward approach.

What injection changes

Injection bypasses digestion, which is the case for it. What it does not settle is whether the intact tripeptide then enters cells efficiently — glutathione functions inside cells, and cellular uptake of the whole molecule is not a given.

That is the same unresolved question as with injectable NAD+: bypassing the gut is not the same as reaching the compartment where the molecule works.

The skin-lightening use

Much of the demand for injectable glutathione concerns skin lightening, via inhibition of melanin synthesis. This use has attracted specific regulatory attention in several countries, with warnings issued about unapproved intravenous products.

Two things are worth separating: whether the mechanism is plausible, and whether unregulated intravenous administration is a reasonable way to pursue it.

The vial math

Glutathione vials are large by peptide standards, because the amounts discussed are in hundreds of milligrams.

As with NAD+, the volumes involved are far larger than a typical peptide vial, and much of a reconstituted vial may expire before use. The storage guide covers that constraint.

Storage

Storage is the same as any reconstituted vial: 2–8 °C, protected from light, never frozen, and bounded by the shorter of peptide stability and the 28-day limit on bacteriostatic water. The bacteriostatic water guide covers the detail.

Frequently asked questions

Is glutathione a peptide?

Yes — a genuine tripeptide, unlike several compounds sold alongside it that are small molecules.

Is oral glutathione useless?

Intact absorption is limited. Precursors such as N-acetylcysteine are the more mechanistically direct route to raising synthesis.

Does it lighten skin?

The proposed mechanism is inhibition of melanin synthesis. Unapproved intravenous products for this purpose have drawn regulatory warnings in several countries.