NAC
N-acetylcysteine / N-acetyl cysteine · Foundation
A glutathione precursor with a genuine hospital pedigree and a much thinner case for the things it is sold for.
What the evidence says
Acetylcysteine is the standard antidote for paracetamol overdose in both oral and IV forms — real, definitive emergency medicine, and not something a retail capsule extrapolates from. Oral NAC has reasonable evidence as a mucolytic in chronic bronchitis and COPD, and a genuinely interesting but mixed psychiatric literature (trichotillomania and OCD-spectrum trials are the strongest of a small set). Its popular framing as a general detox or liver supplement outruns all of that.
What studies used
Trials commonly used 600–1,800 mg/day orally. Published studies had not established a preferred timing.
Reported from published studies and product labelling — a record of what was used in research, not a recommendation. What is right for you is a conversation with a clinician.
Watch out for
- The FDA treats NAC as excluded from the dietary-supplement definition because it was approved as a drug first, while exercising enforcement discretion for otherwise-lawful products — so it sells widely on a policy position rather than a settled legal status
- Can cause nausea and GI upset; asthma patients should be cautious with high doses
Evidence base
established literature
Large human evidence base: several phase 3 or 4 trial reports, plus multiple meta-analyses or systematic reviews.
This letter measures how much human research exists, not whether it works for you — the tier above (Moderate) is the read on quality.
Research (12)
- Supplementing Glycine and N-Acetylcysteine (GlyNAC) in Older Adults Improves Glutathione Deficiency, Oxidative Stress, Mitochondrial Dysfunction, Inflammation, Physical Function, and Aging Hallmarks: A Randomized Clinical TrialJ Gerontol A Biol Sci Med Sci · 2023
- Glycine and N-acetylcysteine (GlyNAC) supplementation in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, insulin resistance, endothelial dysfunction, genotoxicity, muscle strength, and cognition: Results of a pilot clinical trialClin Transl Med · 2021
- Interventions for paracetamol (acetaminophen) overdoseCochrane Database Syst Rev · 2018
- N-acetylcysteine supplementation improves endocrine-metabolism profiles and ovulation induction efficacy in polycystic ovary syndromeJ Ovarian Res · 2024
- Effect of high-dose N-acetylcysteine on exacerbations and lung function in patients with mild-to-moderate COPD: a double-blind, parallel group, multicentre randomised clinical trialNat Commun · 2024
- Effectiveness of N-acetylcysteine in autism spectrum disorders: A meta-analysis of randomized controlled trialsAust N Z J Psychiatry · 2021
- N-acetylcysteine reduces serum creatinine, blood urea nitrogen, symmetric dimethylarginine and urine protein to creatinine ratio in cats with chronic kidney disease: a double-blind, placebo-controlled clinical trialBMC Vet Res · 2026
- Contrast-induced nephropathyJ Vasc Surg · 2011
- Efficacy of N-acetylcysteine and motivational enhancement therapy for nicotine addiction: A randomized clinical trialNarra J · 2025
- Co-administration of vitamin D and N-acetylcysteine to modulate immunosenescence in older adults with vitamin D deficiency: a randomized clinical trialFront Immunol · 2025
- Cysteine, cystine or N-acetylcysteine supplementation in parenterally fed neonatesCochrane Database Syst Rev · 2006
- A randomized, double-blind, placebo-controlled trial of N-acetylcysteine as an adjuvant treatment for alcohol use disorderBraz J Psychiatry · 2025
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