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NAC (N-acetylcysteine / cysteine)

A cysteine source that fuels glutathione — antioxidant, mucolytic, a hospital antidote, and a real psychiatry research story.

Reviewed by Bodil Isaksson, Licensed Biomedical Scientist (Sweden)Last reviewed July 2026Supplement guide

SupplementsAmino acidsAntioxidantLiver

NAC is a stable form of the amino acid cysteine, the limiting building block for the body's master antioxidant, glutathione. It bridges everyday supplement and genuine medicine.

Key takeaways

  • NAC supplies cysteine → glutathione, the body's master antioxidant.
  • It has proven medical uses: a mucus-thinner and the antidote for paracetamol (acetaminophen) overdose.
  • There's provisional evidence in psychiatry — OCD, addiction, some mood/compulsive disorders.1
  • Generally well tolerated; effects likely go beyond antioxidant action (glutamate, inflammation).

What it is

N-acetylcysteine is a more stable, better-absorbed form of cysteine. Cysteine is the rate-limiting amino acid for making glutathione, so NAC effectively raises antioxidant capacity.

The evidence

Beyond its established roles as a mucolytic and overdose antidote, reviews report provisional benefit across several psychiatric conditions (addiction, compulsive/grooming disorders, schizophrenia, bipolar), likely via glutamate and inflammatory pathways as well as glutathione.1

Dose & how to use

Supplement studies commonly use 600–1200 mg/day (psychiatric research often higher, under supervision). Medical uses are dosed by clinicians.

Safety & who benefits

Well tolerated; occasional GI upset. Of interest for antioxidant/glutathione support and as an adjunct in specific conditions — those cases warrant medical guidance.

Bottom line: a genuine crossover between supplement and medicine — solid for glutathione and defined medical uses, promising but still provisional in psychiatry.

References

Adult research summary for education, not a prescription. These are food supplements, not treatments for disease.

  1. Dean O, Giorlando F, Berk M. N-acetylcysteine in psychiatry: current therapeutic evidence and potential mechanisms of action. J Psychiatry Neurosci 2011. pmc.ncbi.nlm.nih.gov

This article summarises nutrition and exercise science for education. It is not a substitute for individual medical advice; consult a professional before starting a supplement, in pregnancy, or alongside medication.