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Moderate evidenceGeneral health

NAC (N-Acetylcysteine)

NAC is a genuine life-saving drug for paracetamol overdose and a reasonable mucolytic in COPD, but the psychiatric and general-wellness claims that drive supplement sales have largely failed in meta-analysis.

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What the science says

  • Standard antidote for paracetamol (acetaminophen) overdose Strong evidence

    NAC restores hepatic glutathione and is the established first-line treatment for paracetamol poisoning, with near-complete prevention of hepatotoxicity when given within 8-10 hours of ingestion. This is intravenous or high-dose oral therapy in hospital and is on the WHO Essential Medicines List; it has nothing to do with a 600 mg capsule taken daily.

  • Reduces exacerbations in COPD and chronic bronchitis Moderate evidence

    Distinct meta-analyses published in 2024 found NAC significantly reduced exacerbation rates in COPD and chronic bronchitis, with benefit most consistent at 1200 mg/day rather than the commonly used 600 mg/day. Effects on lung function and quality of life were much smaller.

  • Psychiatric adjunct claims mostly failed in pooled analysis Limited evidence

    A meta-analysis of double-blind placebo-controlled trials of adjunctive NAC in bipolar depression and major depressive disorder found no significant advantage over placebo on depression scale scores. Schizophrenia meta-analyses show at most small effects on negative symptoms, and the trichotillomania and skin-picking findings rest on a couple of small trials with mixed replication.

  • Antioxidant and general-wellness claims are unproven Limited evidence

    Raising glutathione is a plausible mechanism, but no controlled trial has shown that routine NAC supplementation in healthy adults improves longevity, immunity or exercise recovery. Some exercise studies suggest high-dose antioxidant intake may blunt training adaptations.

Dosage & safety

Studied doseCOPD trials used 600-1200 mg/day, with 1200 mg/day showing the more consistent benefit. Psychiatric trials typically used 2000-2400 mg/day for 12-24 weeks. Paracetamol overdose protocols use weight-based IV dosing in hospital and are not a self-treatment.
SafetyOral NAC commonly causes nausea, vomiting, diarrhea and an unpleasant sulphurous taste and odor. Intravenous NAC can trigger anaphylactoid reactions (rash, flushing, bronchospasm), most often in people with asthma. It may have mild antiplatelet activity and should be used cautiously with anticoagulants and stopped before surgery. Do not combine with nitroglycerin (risk of severe hypotension and headache). Regulatory note: in 2020 the US FDA stated that NAC is excluded from the dietary supplement definition because it was approved as a drug first, and although the agency announced enforcement discretion in 2022, its supplement status in the US remains legally unsettled. In several EU countries NAC is sold as a registered medicine rather than a supplement.

How to take it

TimingTiming does not matter; split larger daily amounts into two doses.
With food?With food, which reduces the nausea and vomiting that are the main reason people quit.
Worth knowingThe sulphurous smell is normal and not a sign the product has spoiled, but keep the bottle tightly closed since NAC oxidises with air and moisture.

Interactions

With medications

  • nitroglycerin and other nitrates

    NAC markedly potentiates nitrate-induced vasodilation, causing severe hypotension and headache. do not combine

  • warfarin, DOACs and antiplatelet drugs

    NAC has mild antiplatelet activity that adds to anticoagulation. tell your prescriber and stop NAC before planned surgery

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

What is NAC good for?

NAC has strong evidence as the hospital antidote for paracetamol overdose and moderate evidence for reducing COPD and chronic bronchitis flare-ups, most consistently at 1200 mg/day. Its general-wellness claims are unproven.

Does NAC help depression or other mental health conditions?

Mostly not — the evidence is limited. A meta-analysis found adjunctive NAC no better than placebo for bipolar or major depression, and effects in schizophrenia are small at most.

How much NAC per day?

COPD trials used 600–1200 mg/day of NAC, with 1200 mg/day showing more consistent benefit; psychiatric trials used 2000–2400 mg/day. Take NAC with food to reduce nausea.

Is NAC safe with nitroglycerin or blood thinners?

Do not combine NAC with nitroglycerin, as it can cause severe hypotension and headache. NAC also has mild antiplatelet activity, so tell your prescriber if you are anticoagulated and stop it before surgery.

Scientific references

Where to buy

NOW Foods, NAC, 600 mg, 250 Capsules

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