NAC (N-Acetyl Cysteine) Dosage Chart
N-Acetyl Cysteine (NAC) is the precursor to glutathione, the body's master antioxidant. Used medically at high doses for acetaminophen overdose and as a mucolytic for respiratory conditions (COPD, chronic bronchitis). At supplement doses, NAC supports liver health, reduces oxidative stress, and has emerging evidence for OCD and bipolar disorder adjunct therapy.
NAC (N-Acetyl Cysteine) Dosage by Age Group
| Age Group | Age Range | Dose Range | Notes |
|---|---|---|---|
| Adults — antioxidant / liver support | 18–64 years | 600–1800 mg | 600 mg 1–3× daily; most supplements are 600 mg per capsule |
| Adults — respiratory health | 18–64 years | 600–1200 mg | Mucolytic dose; 600 mg twice daily |
| Adults — OCD adjunct (psychiatric) | 18–64 years | 2400–3000 mg | 2,400–3,000 mg/day in trials; physician-supervised |
| Seniors (65+) | 65+ years | 600–1200 mg | Standard supplement range; supports glutathione which declines with age |
When and how to take NAC (N-Acetyl Cysteine)
Take with or without food. Many people take NAC on an empty stomach in the morning for antioxidant effects. For respiratory use, twice-daily dosing with meals reduces nausea.
Available Forms
Standard form. 600 mg per capsule is most common.
Plain NAC has a sulfurous smell — normal, not a quality indicator
Dissolve in water; used in European respiratory medicine (ACC, Fluimucil).
600–1,200 mg per sachet/tablet; pleasant to take
Used in hospitals for acetaminophen overdose; extremely high doses.
Not available OTC; IV protocol is specific to emergency use
Safety Cautions
- High doses (above 1,800 mg/day) may cause nausea, diarrhea, or vomiting — start at 600 mg/day.
- FDA classified NAC as a drug ingredient in 2020 based on pre-IND history, creating regulatory uncertainty for supplements — product availability may vary.
- May interact with nitroglycerin (increase headache) and activated charcoal (reduces NAC absorption).
- Avoid in people with asthma — inhaled NAC can cause bronchospasm (this applies to nebulized form, not oral).
- May potentiate blood pressure-lowering medications.
Frequently Asked Questions
How much NAC should I take for liver health?
For liver support and antioxidant function, 600–1,200 mg per day is the standard supplement dose. Most NAC capsules are 600 mg; start with one capsule daily and increase to twice daily if tolerated. Studies supporting liver health typically used 600 mg taken twice daily.
Is NAC still available as a supplement?
NAC availability has been uncertain since 2020 when the FDA issued warning letters to some sellers, citing its prior use as a drug ingredient. However, NAC continues to be sold by many supplement companies. The situation remains unresolved. Check current product availability from reputable suppliers.
Does NAC increase glutathione?
Yes. NAC is a rate-limiting precursor to glutathione synthesis — it provides cysteine, the amino acid that limits how much glutathione the body can produce. Oral NAC reliably increases blood and tissue glutathione levels. This is the primary mechanism for NAC's antioxidant, liver-protective, and cellular protective effects.
Sources & References
- Tenório MCDS et al., Oxidative Med Cell Longev 2021 — NAC antioxidant review
- Millea PJ, Am Fam Physician 2009 — N-acetylcysteine: multiple clinical applications
- EASL Clinical Guidelines: Drug-induced Liver Injury