NAC (N-Acetyl Cysteine)
Amino Acid DerivativeAlso known as: NAC · N-acetylcysteine · N-acetyl-L-cysteine
A precursor to glutathione, the body's primary endogenous antioxidant. Used medically for acetaminophen overdose. Studied for respiratory health, OCD, addiction, and oxidative stress. Regulatory status has varied.
How expert claims hold up
105 of 105 claims assessed46 of 105 assessed claims supported or partially supported by published research
Expert Consensus
Dose divergence: Experts recommend different amounts (600–1800milligrams, 600-1200milligrams). Check the Stack & Timing tab for study-backed dosing ranges.
Evidence Summary
The research on NAC (N-Acetyl Cysteine) spans a wide range of health conditions, including aging, lung disease, obsessive-compulsive disorder, polycystic ovary syndrome (PCOS), kidney protection, and athletic recovery. Across the available studies — including several meta-analyses, RCTs, and reviews — NAC shows consistent biological plausibility as a glutathione precursor and antioxidant, but the clinical evidence is uneven across conditions. The strongest signals come from its role in restoring glutathione levels and reducing oxidative stress, particularly in older adults and those with chronic conditions. However, the majority of expert claims about NAC (roughly 56%) were rated as having insufficient evidence, and only 2 out of 105 claims were fully supported, signaling that enthusiasm for NAC frequently outpaces what the current human data can confirm.
Read full evidence summary →Top studies
The effects of N-acetylcysteine on recovery biomarkers: A systematic review and meta-analysis of controlled trials.
The effects of N-acetylcysteine on recovery biomarkers: A systematic review and meta-analysis of controlled trials.
Economic Evaluation of Neoadjuvant Versus Adjuvant Chemotherapy in Cancer Treatment: A Systematic Review and Meta-Analysis.
Economic Evaluation of Neoadjuvant Versus Adjuvant Chemotherapy in Cancer Treatment: A Systematic Review and Meta-Analysis.
Expert Mentions
All 105 mentions
“High doses can cause nausea and GI upset.”
High doses of NAC can cause nausea and GI upset.
None of the 10 provided studies report key findings, populations, or limitations that directly address the side effect profile of high-dose NAC supplementation, including nausea and GI upset. While se…
“the FDA briefly attempted to remove NAC from the supplement market after a company tried to patent it as a drug. It's currently still available as a supplement, but this regulatory uncertainty is worth tracking.”
The FDA briefly attempted to remove NAC from the supplement market after a company tried to patent it as a drug, and this regulatory uncertainty is worth tracking.
None of the 10 provided PubMed studies address the regulatory history of NAC, FDA actions regarding its classification, or patent-related market removal attempts. The claim is about a specific regulat…
Safety, interactions & who should avoid NAC (N-Acetyl Cysteine)
generally_recognized_safe
NAC has a generally recognized safety profile at commonly used oral doses, with no serious adverse events prominently flagged across the reviewed studies. However, the available evidence does not provide systematic long-term safety data for oral supplementation in healthy populations, and intravenous formulations used in clinical trials carry a different risk profile than over-the-counter supplements.
NAC is generally considered well-tolerated at doses studied (600–1800 mg/day); the most common adverse effects are gastrointestinal (nausea, vomiting, diarrhea), which can be mitigated by taking with food. At very high doses used clinically (IV for acetaminophen overdose), adverse effects are more pronounced but are not relevant to oral supplementation ranges. There is theoretical concern that high-dose antioxidant supplementation, including NAC, may attenuate beneficial adaptive responses to exercise (e.g., mitochondrial biogenesis).
Who should avoid it
Individuals with asthma should use caution as inhaled NAC can cause bronchospasm (less relevant for oral forms but worth noting). Those with active peptic ulcer disease or bleeding disorders should consult a healthcare provider before use. Pregnant or breastfeeding individuals should seek medical guidance, as safety data in these populations from supplementation trials is limited. People on nitrates or anticoagulants should consult a physician prior to use.
Known interactions
- ·Nitroglycerin and other nitrates: NAC may potentiate vasodilatory effects, potentially causing hypotension and headache
- ·Activated charcoal: may reduce oral NAC absorption if taken simultaneously
- ·Immunosuppressants: theoretical interaction via immune modulation; use with caution and medical supervision
- ·Anticoagulants (e.g., warfarin): NAC may have mild antiplatelet or anticoagulant properties; monitor if combined
Pregnancy & breastfeeding
Our sources specifically flag pregnancy or breastfeeding considerations for NAC (N-Acetyl Cysteine) — see the cautions above.
We don’t assign pregnancy-safety ratings. Many supplements lack adequate safety data in pregnancy and breastfeeding, and the absence of a warning here does not mean a supplement is safe to take. Don’t start, stop, or continue any supplement while pregnant or nursing without your OB-GYN or midwife.
Read: Supplements during pregnancy & breastfeeding →This is educational information only. Consult a healthcare provider before starting any supplement.
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Key findings
- ·GlyNAC supplementation (NAC + glycine combined) improved multiple aging biomarkers in older adults in a small RCT, including glutathione levels, oxidative stress markers, and physical function.
- ·Strong-quality meta-analyses support NAC's role in reducing contrast-induced kidney injury, particularly when administered intravenously in clinical settings.
- ·Moderate-quality RCT evidence suggests oral NAC may improve hormonal and metabolic markers in women with PCOS.
Evidence gaps
- ·Most studies do not isolate oral NAC supplementation from combination protocols (e.g., GlyNAC), making it difficult to determine how much benefit is attributable to NAC alone at typical consumer doses.
- ·Long-term safety and efficacy data from large RCTs using oral NAC in healthy or aging populations are absent from this evidence set, leaving durability and optimal dosing unknown.
- ·Evidence across psychiatric and neurodevelopmental applications (e.g., OCD) remains preliminary, with no strong-quality RCTs or meta-analyses in this set to support clinical recommendations.