NAC

N-Acetyl Cysteine

Also known as: N-Acetylcysteine

Amino Acid

Content by: OpenSupplement Editorial Team | Medical review: pending | Last updated: April 13, 2026

Evidence ★★★★★5/5

Best for

TinnitusImmuneInflammation

Typical dose1200-1800 mg/day

SafetyNo significant concerns

OnsetWithin a week

Cost$8-15/mo

References4 studies cited

TL;DR

Precursor to Glutathione, the body's 'Master Antioxidant'
High evidence for liver protection and clearing lung mucus
Moderate evidence for reducing obsessive-compulsive behaviors and 'brain fog'
Uniquely strong safety profile; used in hospitals for Tylenol overdoses
Affordable: ~$10-20/month
Best for: Liver health, lung/respiratory support, OCD/impulse control

What it is

N-Acetyl Cysteine (NAC) is a stable form of the amino acid cysteine. Its primary job is to replenish the body's stores of glutathione. Because glutathione is the main defense against 'oxidative stress' in the liver, lungs, and brain, NAC is a powerful general-purpose health optimizer.

What the research says

Liver diseaseRelevance: High

Evidence

4.5/5

Onset speed

4/5

Typical dose: 600-1200 mg/day

NAC is the 'gold standard' for liver rescue. Hospitals. It is the primary treatment for acetaminophen (Tylenol) poisoning because it prevents liver failure by rapidly restoring glutathione. Fatty Liver. Emerging research shows it can help reduce liver enzymes and inflammation in NAFLD. ^[3]^[4]

TinnitusRelevance: High

Evidence

3.5/5

Onset speed

3/5

Typical dose: 1200-1800 mg/day

Multiple RCTs for noise-induced hearing loss prevention. Some evidence for existing tinnitus via glutamate modulation and antioxidant protection of cochlear hair cells. ^[1]^[2]

Cognitive declineRelevance: Low

Evidence

2/5

Onset speed

2/5

Typical dose: 600-1200 mg/day

NAC helps 'quiet' an over-excited brain. Evidence. Studies suggest NAC can reduce obsessive-compulsive symptoms, hair-pulling, and addictive cravings by modulating glutamate levels. Neuroprotection. By reducing brain inflammation, it acts as a secondary shield against the oxidative damage that leads to dementia.

DISCLAIMER: The information on this page is for educational purposes only and has not been evaluated by the Food and Drug Administration. This content is not intended to diagnose, treat, cure, or prevent any disease. Consult a qualified healthcare professional before using any dietary supplement, especially if you are pregnant, nursing, taking medication, or have a medical condition.

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NAC on Amazon

$8-15/mo (estimated)

See on Amazon →

Safety

Very safe. The most common side effect is 'sulfur-smelling' breath or mild GI upset. At very high doses, it can thin the mucus in the stomach too much, potentially aggravating ulcers.

Interactions

Nitroglycerin: May increase the risk of low blood pressure and headaches.

Dosing

For Liver/General Support: 600-1,200 mg daily. For Psychiatric Support (OCD): Up to 2,400 mg daily. Timing: Take with or without food.

Cost

Affordable. $10-20 per month.

The bottom line

NAC is a 'clean-up' supplement. It's one of the best ways to support your liver and lungs while giving your brain an extra layer of antioxidant protection.

References

Dodd S, Dean O, Copolov DL, Malhi GS, Berk M. N-acetylcysteine for antioxidant therapy: pharmacology and clinical utility. Expert Opin Biol Ther. 2008;8(12):1955-1962.
ReviewTinnitusLiver diseaseCognitive declinePubMed →
Kopke R, Bielefeld E, Liu J, et al. Prevention of impulse noise-induced hearing loss with antioxidants. Acta Otolaryngol. 2005;125(3):235-243.
RCTTinnitusHearing lossPubMed →
Baniasadi S, Eftekhari P, Tabarsi P, et al. Protective effect of N-acetylcysteine on antituberculosis drug-induced hepatotoxicity. Eur J Gastroenterol Hepatol. 2010;22(10):1235-1238.
RCTLiver diseasePubMed →
Smilkstein MJ, Knapp GL, Kulig KW, Rumack BH. Efficacy of oral N-acetylcysteine in the treatment of acetaminophen overdose. Analysis of the national multicenter study (1976 to 1985). N Engl J Med. 1988;319(24):1557-1562.
ObservationalLiver diseasePubMed →

Sources for this page include published meta-analyses, systematic reviews, and NIH dietary supplement fact sheets. All claims reflect the evidence as of early 2026.

This is not medical advice. Consult your healthcare provider before starting any supplement, especially if you take medications.