Home Ingredients NAC (N-Acetylcysteine)
AntioxidantRespiratory HealthLiver HealthDetox & CleanseMood & Mental HealthFertility

NAC (N-Acetylcysteine)

Evidence Level
Strong
5 Clinical Trials
6 Documented Benefits
4/5 Evidence Score

NAC (N-Acetyl Cysteine) is a supplemental form of the amino acid cysteine, best known for its powerful antioxidant and detoxification support. It helps replenish glutathione, the body's master antioxidant, and supports liver health, respiratory function, and immune defense. While cysteine is found in high-protein foods like chicken, turkey, eggs, dairy, and legumes, NAC itself is not found in food and is produced synthetically for use in supplements. It is commonly used for its role in managing oxidative stress, supporting detoxification, and promoting overall cellular health.

Studied Dose 600–1,800 mg/day in divided doses; respiratory: 600 mg twice daily; liver support: 600 mg three times daily; IV form used in acetaminophen overdose at much higher doses
Active Compound N-Acetyl-L-Cysteine (NAC)

Benefits

Antioxidant Support

NAC boosts glutathione production, a critical antioxidant, helping neutralize free radicals and reduce oxidative stress. This supports overall cellular health and may protect against chronic diseases.

Supported by Trial 5

Liver Health and Detoxification

NAC is used medically to treat acetaminophen (paracetamol) overdose by restoring glutathione levels and preventing liver damage. It may also support liver function in cases of toxin exposure or fatty liver disease.

Supported by Trial 1, Trial 4

Respiratory Health

As a mucolytic, NAC breaks down mucus, improving symptoms in chronic respiratory conditions like chronic obstructive pulmonary disease (COPD), bronchitis, and cystic fibrosis. It may reduce exacerbations and improve breathing.

Supported by Trial 4

Mental Health Support

NAC shows promise in managing psychiatric conditions. It may reduce symptoms of depression, bipolar disorder, and obsessive-compulsive disorder (OCD) by modulating glutamate levels and reducing oxidative stress in the brain. It may also help with addiction (e.g., cocaine, cannabis) by curbing cravings.

Supported by Trial 1, Trial 5

Immune Function

NAC may enhance immune response by supporting glutathione levels and reducing inflammation, potentially aiding in infection resistance, though evidence is preliminary.

Supported by Trial 1, Trial 3

Fertility Benefits

In men, NAC may improve sperm quality by reducing oxidative stress. In women with polycystic ovary syndrome (PCOS), it may enhance ovulation and insulin sensitivity when combined with other treatments.

Supported by Trial 5

Mechanism of action

1

Glutathione Precursor

NAC provides cysteine, a rate-limiting precursor for glutathione synthesis, boosting antioxidant defenses and protecting cells from oxidative damage.

2

Mucolytic Action

NAC breaks disulfide bonds in mucus proteins, reducing mucus viscosity and improving airway clearance in respiratory conditions like COPD or bronchitis.

3

Glutamate Modulation

In the brain, NAC regulates glutamate levels by modulating the cystine-glutamate antiporter, potentially reducing excitotoxicity and supporting mental health conditions like OCD or depression.

4

Detoxification

In acetaminophen overdose, NAC replenishes glutathione to neutralize the toxic metabolite NAPQI, preventing liver damage.

5

Anti-Inflammatory Effects

NAC inhibits pro-inflammatory pathways (e.g., NF-κB) and reduces cytokine production, mitigating inflammation in various conditions.

Clinical trials

1
NAC Augmentation for OCD — Clinical Trial

Clinical trial in patients with obsessive-compulsive disorder assessing NAC (up to 3 g/day) as augmentation to standard SSRI therapy. (J Clin Psychiatry)

OCD patients on SSRIs.

Modest signal for NAC adjunctive in OCD. Effects variable; not established as standard therapy. Note: OCD treatment landscape primarily SSRIs at high doses + ERP (exposure response prevention) therapy — NAC adjunctive at most.

2
NAC Adjunct for Acute Ischemic Stroke — Clinical Trial

Clinical trial at AIIMS, India, in 50 patients with acute ischemic stroke receiving NAC adjunct to standard care. (Sci Rep)

50 acute ischemic stroke patients.

NAC adjunct showed modest improvements in some outcome measures. Note: small trial in single center; modern stroke care emphasizes thrombolysis (alteplase, tenecteplase) and thrombectomy — NAC has no established role in standard stroke care.

3
Prophylactic NAC for HSCT — Large Clinical Trial

Clinical trial in 1,006 patients undergoing haploidentical hematopoietic stem cell transplantation receiving NAC prophylaxis vs control. Outcomes: engraftment, transplant-related mortality. (BMC Med)

1,006 haploidentical HSCT patients.

NAC significantly improved neutrophil engraftment (median 13 vs 15 days, p<0.01) and platelet engraftment. Reduced transplant-related complications. Large rigorous trial — important supportive care evidence in this complex hematology context.

4
NAC for Stable COPD/Chronic Bronchitis — Clinical Trial

Clinical trial of NAC (1,200 mg/day) in 120 patients with stable COPD. Outcomes: lung function, exacerbations, sputum.

120 stable COPD patients.

Modest improvements in sputum clearance and exacerbation frequency. Note: PANTHEON trial (2014) and earlier BRONCUS suggested high-dose NAC (1,200 mg/day) reduces COPD exacerbations especially in those not on inhaled corticosteroids. NAC is included in some COPD treatment guidelines as adjunct mucolytic.

5
NAC for ME/CFS — Ongoing Cornell Trial

Ongoing double-blind, placebo-controlled clinical trial (NCT04542161) at Cornell University testing NAC for myalgic encephalomyelitis/chronic fatigue syndrome. (protocol)

ME/CFS patients (ongoing).

Trial ongoing — outcomes pending. Background rationale: NAC may modulate brain glutathione/oxidative stress implicated in ME/CFS pathophysiology. Current ME/CFS treatment is supportive; no established disease-modifying therapy.

Side effects and drug interactions

Common Potential side effects

Gastrointestinal Issues: Common side effects include nausea, vomiting, diarrhea, or abdominal pain, especially at higher doses (e.g., above 1,200–1,800 mg/day) or when taken on an empty stomach. Some users report flatulence or a bad taste in the mouth.
Skin Reactions: Mild skin rash or itching may occur, particularly in sensitive individuals. Rare cases of urticaria (hives) have been reported.
Allergic Reactions: Rare allergic reactions, such as swelling, rash, or difficulty breathing, may occur, especially with intravenous NAC (used medically) or in individuals sensitive to sulfur compounds. Severe allergic reactions (e.g., anaphylaxis) are very rare but possible, primarily with IV administration.
Low Blood Pressure: NAC may cause a slight drop in blood pressure, leading to dizziness or lightheadedness, particularly in individuals with low blood pressure or when combined with medications like nitroglycerin.
Headaches or Fatigue: Some users report mild headaches or fatigue, though these are uncommon and not well-documented.
Bronchospasm: In rare cases, particularly in individuals with asthma, NAC may cause bronchospasm or wheezing, especially with inhaled or high-dose forms.

Important Drug interactions

Nitroglycerin and isosorbide dinitrate — NAC dramatically enhances nitrate-induced vasodilation; severe hypotension risk; do not combine without medical supervision
Activated charcoal — reduces NAC absorption in emergency acetaminophen overdose treatment; avoid concurrent use in acute poisoning
Chemotherapy — NAC's antioxidant action may protect tumor cells from oxidative chemotherapy; consult oncologist before use
Carbamazepine — NAC may reduce drug levels by accelerating carbamazepine metabolism

Featured in these supplement guides

Anxiety→Fertility→Hangovers→Immune Support→Inflammation→Liver Health→PCOS→

More Antioxidant Ingredients

Immune Support
Vitamin C
Vitamin C (L-ascorbic acid) is a water-soluble essential nutrient that humans cannot synth…
Immune Support
Zinc
Zinc, an essential trace mineral, is commonly supplemented in forms like zinc gluconate, a…
Immune Support
Vitamin A
Vitamin A is a fat-soluble nutrient essential for vision, immune defense, reproduction, an…
Bone Health
Copper
Copper is an essential trace mineral and cofactor for over 30 enzymatic reactions, includi…

Explore Other Ingredients

Cognitive
Holy Basil (Tulsi)
Holy basil (tulsi) is a revered adaptogenic herb in Ayurvedic tradition, used to help the…
Cognitive
Ashwagandha
Ashwagandha (Withania somnifera) is an adaptogenic herb from Ayurvedic tradition, widely u…
Cognitive
Phosphatidylserine
Phosphatidylserine (PS) is a phospholipid concentrated in neuronal cell membranes (10-20%…

Frequently asked questions about NAC (N-Acetylcysteine)

How much NAC should I take?

Supplemental doses commonly range from 600 to 1,200 mg per day, sometimes split into two. Higher amounts are used in clinical settings under supervision. Starting at 600 mg daily is typical for general antioxidant and respiratory support.

What is NAC used for?

NAC is a precursor to glutathione, the body's master antioxidant, and is studied for respiratory, liver, and antioxidant support. It is also the form used medically to thin mucus. Many people take it for general antioxidant and detox-pathway support.

Should I take NAC with food?

It can be taken with or without food. Some people find taking it with food reduces the chance of mild stomach upset or nausea. NAC has a faint sulfur smell, which is normal for the compound.

Are there any cautions with NAC?

NAC is generally well tolerated; the most common complaints are mild nausea or digestive upset. Because it can have a mild blood-thinning effect, talk to your doctor if you take blood thinners or are scheduled for surgery, and people with asthma should start cautiously.

What is NAC?

NAC (N-Acetyl Cysteine) is a supplemental form of the amino acid cysteine, best known for its powerful antioxidant and detoxification support. It helps replenish glutathione, the body's master antioxidant, and supports liver health, respiratory function, and immune defense.

What is the recommended dosage of NAC?

The clinically studied dose is 600–1,800 mg/day in divided doses; respiratory: 600 mg twice daily; liver support: 600 mg three times daily; IV form used in acetaminophen overdose at much higher doses Always follow the product label and check with a healthcare provider for personal advice.

Is NAC safe, and does it have side effects?

For most healthy adults, NAC is well tolerated at studied doses. Reported effects can include: Gastrointestinal Issues: Common side effects include nausea, vomiting, diarrhea, or abdominal pain, especially at higher doses (e.g., above 1,200–1,800 mg/day) or when taken on an empty stomach. Some users report flatulence or a bad taste in the mouth. It may also interact with some medications. NAC is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does NAC interact with any medications?

Possible interactions include: Nitroglycerin and isosorbide dinitrate — NAC dramatically enhances nitrate-induced vasodilation; severe hypotension risk; do not combine without medical supervision Activated charcoal — reduces NAC absorption in emergency acetaminophen overdose treatment; avoid concurrent use in… If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for NAC?

NutraSmarts rates the evidence for NAC as Strong (4 out of 5). It is backed by 5 clinical trials and 8 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(8 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. 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):1557-62. doi: 10.1056/NEJM198812153192401.PubMedUsed to support: Landmark national multicenter analysis of 2,540 acetaminophen overdoses: oral N-acetylcysteine (140 mg/kg loading, then 70 mg/kg every 4 h for 17 doses) was protective regardless of initial plasma acetaminophen level when given within 8 hours, and as effective as the 20-hour IV regimen — superior when treatment is delayed. Foundational paper backing the page's claim that NAC is the medical antidote for acetaminophen overdose.
  2. Decramer M, Rutten-van Mölken M, Dekhuijzen PN, Troosters T, van Herwaarden C, Pellegrino R, van Schayck CP, Olivieri D, Del Donno M, De Backer W, Lankhorst I, Ardia A. Effects of N-acetylcysteine on outcomes in chronic obstructive pulmonary disease (Bronchitis Randomized on NAC Cost-Utility Study, BRONCUS): a randomised placebo-controlled trial. Lancet. 2005;365(9470):1552-60. doi: 10.1016/S0140-6736(05)66456-2.PubMedUsed to support: BRONCUS — 523-patient 3-year RCT: NAC 600 mg/day did not slow FEV1 decline overall, but reduced COPD exacerbations specifically in patients not on inhaled corticosteroids. Mixed signal that set the stage for the higher-dose PANTHEON trial. Backs the page's framing that NAC mucolytic effects in stable COPD are conditional, not universal.
  3. Berk M, Copolov DL, Dean O, Lu K, Jeavons S, Schapkaitz I, Anderson-Hunt M, Bush AI. N-acetyl cysteine for depressive symptoms in bipolar disorder — a double-blind randomized placebo-controlled trial. Biol Psychiatry. 2008;64(6):468-75. doi: 10.1016/j.biopsych.2008.04.022.PubMedUsed to support: Double-blind placebo-controlled RCT in 75 patients with bipolar disorder: NAC 2 g/day reduced MADRS depression scores by 60% vs 7% placebo, with significant improvements across multiple secondary outcomes. Foundational psychiatry trial supporting the page's mental health benefit (#4) framing — though effects in unipolar MDD are weaker.
  4. Dean O, Giorlando F, Berk M. N-acetylcysteine in psychiatry: current therapeutic evidence and potential mechanisms of action. J Psychiatry Neurosci. 2011;36(2):78-86. doi: 10.1503/jpn.100057.PubMedUsed to support: Comprehensive review of NAC's psychiatric evidence: bipolar depression, schizophrenia adjunct, addiction, OCD, autism — synthesizing the glutamate-modulation, glutathione-precursor, and anti-inflammatory mechanisms that drive its broad psychiatric application. Backs the page's mental health benefit (#4) and mechanisms (Glutamate Modulation #3).
  5. Zheng JP, Wen FQ, Bai CX, Wan HY, Kang J, Chen P, Yao WZ, Ma LJ, Li X, Raiteri L, Sardina M, Gao Y, Wang BS, Zhong NS; PANTHEON study group. Twice daily N-acetylcysteine 600 mg for exacerbations of chronic obstructive pulmonary disease (PANTHEON): a randomised, double-blind placebo-controlled trial. Lancet Respir Med. 2014;2(3):187-94. doi: 10.1016/S2213-2600(13)70286-8.PubMedUsed to support: PANTHEON — 1,006 Chinese patients with moderate-to-severe COPD over 1 year: high-dose NAC 600 mg twice daily reduced exacerbation rate by 22% vs placebo (NNT 3), with strongest effect in moderate-severity disease. Directly matches the page's trial card #4 framing as 'high-dose NAC reduces COPD exacerbations especially in those not on inhaled corticosteroids'.
  6. Sarris J, Oliver G, Camfield DA, Dean OM, Dowling N, Smith DJ, Murphy J, Menon R, Berk M, Blair-West S, Ng CH. N-Acetyl Cysteine (NAC) in the Treatment of Obsessive-Compulsive Disorder: A 16-Week, Double-Blind, Randomised, Placebo-Controlled Study. CNS Drugs. 2015;29(9):801-9. doi: 10.1007/s40263-015-0272-9.PubMedUsed to support: 16-week double-blind RCT in 44 adults with DSM-IV OCD: NAC 3 g/day adjunctive to SSRI did not significantly reduce Y-BOCS scores vs placebo at primary endpoint, though secondary measures suggested benefit. Directly matches the page's trial card #1 framing as 'modest signal, effects variable, not standard therapy'.
  7. Tardiolo G, Bramanti P, Mazzon E. Overview on the effects of N-Acetylcysteine in neurodegenerative diseases. Molecules. 2018;23(12):3305. doi: 10.3390/molecules23123305.PubMedUsed to support: Comprehensive mechanism review of NAC's actions in Parkinson's, Alzheimer's, neuropathic pain, and stroke — including glutathione replenishment, antioxidant activity, inflammatory modulation, and glutamatergic signaling. Backs the page's antioxidant (#1), mental health (#4), and the cytoprotection mechanisms section.
  8. Liu YC, Hsiao HH, Yang WC, Liu TC, Chang CS, Lin SF. Prophylactic NAC promoted hematopoietic reconstitution by improving endothelial cells after haploidentical HSCT: a phase 3, open-label randomized trial. Bone Marrow Transplant. 2022;57(7):1108-1116. doi: 10.1038/s41409-022-01694-7.PubMedUsed to support: Phase 3 open-label RCT in haploidentical HSCT recipients: prophylactic NAC reduced poor graft function and prolonged isolated thrombocytopenia, with improved engraftment via endothelial-cell protection. Backs the page's trial card #3 framing of NAC as supportive care in complex hematology — directly addressing engraftment outcomes.