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  • 67 compound profiles, every source cited
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Research profile · Peptide

Glutathione

Also known as GSH, Gamma-glutamylcysteinylglycine

Early human — evidence level 3 of 4: Early human evidenceUnlicensed — UK regulatory status: Unlicensed medicinal product (UK)

Overview

The cell’s principal low-molecular-weight thiol antioxidant. No injectable glutathione product holds a UK marketing authorisation.

Category
Peptide
Highest evidence level identified
Early human evidence
Last scientifically reviewed
22 August 2026
Last regulatory review
22 August 2026

Mechanism under investigation

Glutathione is a tripeptide of glutamate, cysteine and glycine, synthesised in every cell in two ATP-dependent steps, with availability of cysteine usually rate-limiting. Through the thiol of its cysteine it buffers cellular redox state, reduces peroxides via glutathione peroxidases, regenerates other antioxidants, and conjugates electrophilic toxins and drug metabolites via glutathione-S-transferases — the chemistry behind its central role in paracetamol-overdose toxicology. Intracellular concentrations are millimolar; plasma concentrations are roughly a thousand-fold lower, and cells largely synthesise their own rather than importing the intact tripeptide.

Research areas

  • Redox biology
  • Xenobiotic metabolism

These are fields in which the compound has been investigated. Listing a field is not a statement that anything was demonstrated within it.

Current evidence

In-vitro evidence

Cells, tissues or biochemical systems outside a living organism.

One of the most thoroughly characterised molecules in biochemistry: synthesis, recycling by glutathione reductase, conjugation chemistry and compartmentalisation are all textbook material.

Animal evidence

Studies in living non-human animals.

Extensive, from depletion models of oxidative injury to the protective role in xenobiotic toxicity that underpins clinical use of the precursor N-acetylcysteine.

Human observational evidence

Studies observing people without assigning an intervention.

Low glutathione status is associated with ageing and a long list of diseases, but association work of this kind cannot separate cause from consequence.

Clinical-trial evidence

Studies assigning an intervention to human participants.

Thin for supplementation of the tripeptide itself. A six-month randomised trial of oral glutathione reported modest increases in some body stores, against earlier work showing no change in plasma markers; for the intravenous skin-lightening use that drives much of the commercial interest, the dermatology literature’s systematic assessment found the evidence weak, short-term and inadequate to establish either efficacy or safety.

Study limitations

  • Biochemical importance is not evidence that administering the molecule helps: cells make their own glutathione, and delivering the intact tripeptide is an inefficient way to raise it.
  • The oral supplementation literature is small and internally inconsistent.
  • The intravenous skin-lightening literature is dominated by short, small, poorly controlled studies; the practice has drawn safety warnings from regulators in several countries.
  • No dosing regimen, route or duration is supported by an adequate controlled safety dataset.

UK regulatory context

Unlicensed medicinal product (UK)

A product meeting the definition of a medicinal product but holding no UK marketing authorisation.

Source: The Human Medicines Regulations 2012, regulation 46 — prohibition on sale or supply of an unauthorised medicinal product (opens legislation.gov.uk in a new tab) (legislation.gov.uk)

Regulatory classification is jurisdiction-specific. A compound authorised elsewhere is not thereby authorised in the UK, and a supplier’s description of a substance does not determine how it is classified in law. See safety and regulation for the framework and the authoritative sources.

Safety and interpretation

Oral glutathione is sold as a food supplement and is unremarkable at customary amounts. The injectable is a different matter: no glutathione injection holds a UK marketing authorisation, so supplying one as a medicine is prohibited by regulation 46 of the Human Medicines Regulations 2012, and the intravenous use promoted for skin lightening rests on evidence the dermatology literature itself describes as inadequate, with case reports of serious reactions in the same review. An unlicensed injectable with no controlled safety dataset is the combination this site’s safety pages exist to warn about.

References