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Printed from https://bottledhope.co/supplements/n-acetylcysteine/. Last reviewed 2026-09-25. Check the site for the latest version.

N-acetylcysteine (NAC)

A derivative of the amino acid cysteine, sold as a supplement and also approved as a drug. It has been studied for COPD, substance cravings and mental health.

Explained simply · Last reviewed

What it is

N-acetylcysteine, usually shortened to NAC, is a derivative of the amino acid cysteine. NIH’s Office of Dietary Supplements (ODS) describes it as an antioxidant that raises levels of glutathione inside cells. ODS notes that products containing NAC are sold as dietary supplements. The reviews on this page studied it in COPD, in cravings for alcohol, tobacco and other drugs, and in several mental health conditions.

More about N-acetylcysteine (NAC)

NIH’s Office of Dietary Supplements (ODS) describes it as an antioxidant that raises levels of glutathione inside cells. ODS notes that products containing NAC are sold as dietary supplements. The reviews on this page studied it in COPD, in cravings for alcohol, tobacco and other drugs, and in several mental health conditions.

It is also a medicine. According to ODS, an inhaled liquid form is classified in the United States as a drug, not a dietary supplement, and is approved by FDA as a mucolytic, a medicine that loosens mucus. ODS adds that NAC given by mouth or into a vein has FDA approval as a drug to treat acetaminophen (paracetamol) poisoning. These are medical uses of prescription products, not supplement uses. The safety section explains how FDA treats NAC sold as a supplement.

GlyNAC, a combination of glycine and NAC, is a different product, and none of the research on this page is about it.

Also known as: NAC, acetylcysteine, N-acetyl cysteine, N-acetyl-L-cysteine

At a glance

Safety: known risks, 3 groups who should avoid it or take extra care and 3 documented interactions. See Safety ↓

Claims made about N-acetylcysteine (NAC), and how strong the evidence is for each:

Each rating follows our published rules and the sources cited for it. We don’t add our own medical judgment. How we rate

Safety

Read this before the ratings below.

Risks

  • NAC taken by mouth: ODS lists nausea, vomiting, abdominal pain, diarrhea, indigestion and discomfort in the upper stomach as reported side effects. It also states: "No safety concerns have been reported for products labeled as dietary supplements that contain NAC."
  • In trials of NAC for substance use disorders, a 2024 meta-analysis reports stomach upset (such as cramps, discomfort, diarrhea and nausea) and headache as the most common non-serious side effects. Of 16 serious adverse events in the groups given NAC, the authors judged one, a fainting episode, to be possibly related to NAC.
  • Meta-analyses of placebo-controlled trials in COPD (2023 and 2026), OCD (2024) and substance use disorders (2024) found no statistically significant difference in adverse events between NAC and placebo. A result that is not statistically significant is too little evidence to rule out a difference; it does not show that there is none.
  • Inhaled acetylcysteine, a prescription mucolytic: the label of one acetylcysteine solution warns: "Asthmatics under treatment with acetylcysteine should be watched carefully." It adds: "If bronchospasm progresses, this medication should be discontinued immediately." Bronchospasm is a tightening of the airways. The label lists stomatitis (mouth sores), nausea, vomiting, fever, runny nose, drowsiness, clamminess, chest tightness and bronchoconstriction among adverse effects.
  • Intravenous acetylcysteine, a prescription antidote for acetaminophen overdose: the FDA-approved label for Acetadote warns that "serious acute hypersensitivity reactions; including fatal or life-threatening anaphylaxis, rash, hypotension, wheezing, and/or shortness of breath; have been observed in patients receiving intravenous acetylcysteine for acetaminophen overdose", and that patients with asthma should be closely monitored during treatment.
  • Young children: a 2013 Cochrane review of acetylcysteine and carbocysteine, another mucolytic, for acute respiratory tract infections in children states that its results "have to be interpreted with caution because they are based on a limited number of participants included in studies whose methodological quality is questionable". It concludes that both drugs "appear to be safe in children older than two years". It also notes that "very few children under two years of age were involved in the studies", and reports strong safety concerns in that age group.
  • The 2013 Cochrane review of mucolytics in children cites French pharmacovigilance data on 59 respiratory reactions in children younger than six between 1989 and 2008 (28 after acetylcysteine, 30 after carbocysteine and one after both). The reactions included increased bronchial secretions and worsening breathing difficulty, and 51 of the children needed hospital care or a longer stay.
  • The 2013 Cochrane review reports that the outcome of those reactions was favorable in all but two cases: one child developed pleuropneumonia, and a one-year-old girl died of pulmonary edema (fluid in the lungs) "that was considered secondary to mucous vomiting according to the reporting physician". The review does not say which of the two drugs either child had received. It states that these reactions led France and Italy to withdraw the license for both drugs in children younger than two in April 2010.
  • United States regulatory status: in guidance dated August 2022, FDA states that NAC "was approved as a new drug under section 505 of the FD&C Act on September 14, 1963", and that it has determined NAC is excluded from the definition of a dietary supplement "because NAC was approved as a new drug before it was marketed as a dietary supplement or as a food." It records that its joint final response of 31 March 2022 to two citizen petitions denied the requests to find NAC not excluded, and that it was still considering a request to allow NAC in supplements by regulation.
  • The 2022 FDA guidance states FDA’s "intent to exercise enforcement discretion" over the sale of certain NAC products labeled as dietary supplements: those "that would be lawfully marketed dietary supplements if NAC were not excluded". The policy does not apply to products intended to diagnose, cure, mitigate, treat or prevent disease. FDA says that, unless it identifies safety-related concerns, it intends to keep this policy until it either completes rulemaking to allow NAC in supplements ("should we move forward with such proceedings") or denies that request.
  • The 2022 FDA guidance also states that FDA’s "initial review has not revealed safety concerns" with NAC used in or as a dietary supplement, while its "full safety review of NAC remains ongoing". On 29 November 2023, FDA said it had completed its review of safety information on NAC and that the review would go through peer review. As of September 2026, that is the latest FDA statement on NAC this page found.

Who should avoid it or take extra care

  • People with asthma: the labels for both inhaled and intravenous acetylcysteine call for patients with asthma to be watched or monitored closely during that treatment. No cited source addresses asthma and NAC taken by mouth as a supplement.
  • Children younger than two: the 2013 Cochrane review states that, "given strong concerns about safety", acetylcysteine and carbocysteine "should only be used for acute upper and lower RTIs in the context of a RCT with regards to children younger than two years." RTIs are respiratory tract infections, and an RCT is a randomized controlled trial.
  • People taking nitroglycerin, blood thinners or blood pressure medicines: see the interactions below.

Documented interactions

  • Nitroglycerin (used to treat angina): ODS states that the combination of NAC and nitroglycerin "can cause hypotension and severe headaches." Hypotension is low blood pressure. Source [1]
  • Anticoagulants (blood thinners): ODS states that NAC "might have anticoagulant effects", so it could have additive effects if taken with anticoagulants. Source [1]
  • Blood pressure medicines (antihypertensives): ODS states that NAC might reduce blood pressure, so it could have additive effects if taken with antihypertensive medications. Source [1]

Safety sources: Source [1]Source [2]Source [3]Source [4]Source [5]Source [6]Source [7]Source [8]Source [9]Source [10]

What the evidence says

Each claim is rated on its own evidence. Ratings follow the scale on our methodology page.

  • Reduces flare-ups (exacerbations) of COPD, taken regularly by mouth Evidence rating: Limited

    People with COPD take it hoping to have fewer flare-ups of their breathing.

    A 2026 review found fewer people with flare-ups on NAC, a 2023 review found no significant difference, and a Cochrane review found a benefit only at lower doses.

    The reviews disagree, so this page shows the lower rating. A 2026 meta-analysis pooled 11 placebo-controlled trials of NAC taken by mouth in stable COPD. It found that fewer people on NAC had at least one flare-up, and concludes that NAC "may reduce the risk of acute exacerbations".

    The same 2026 review ran a trial sequential analysis, which found that the evidence has not yet reached the amount needed for a firm conclusion. It found no significant improvement in lung function, quality-of-life scores or glutathione levels.

    A 2023 meta-analysis limited to trials published since 2000 found no statistically significant difference in the six trials that reported flare-ups. Its authors conclude that NAC "did not reduce the risk of acute exacerbation".

    A 2019 Cochrane review of all mucolytics taken by mouth states that "when subgrouped by dose or type of mucolytic, we did not observe a consistent effect". It reports significant benefits over placebo for lower doses of NAC, while its subgroups of NAC trials at higher daily doses showed no significant difference. It notes that more recent trials show less benefit than earlier ones. The review graded its evidence only for all mucolytics pooled, not for NAC on its own.

    Sources: Source [1]Source [2]Source [3]

  • Reduces cravings in substance use disorders Evidence rating: Limited

    People trying to stop drinking, smoking or using drugs take it hoping it will quiet their cravings.

    Two 2024 reviews of small trials disagree: one found lower craving ratings with NAC but calls the evidence weak, and the other found no significant difference from placebo.

    Two 2024 meta-analyses of small placebo-controlled trials disagree. The trials covered several substances, including alcohol, tobacco, cocaine and amphetamines.

    One, of 11 trials with 446 people, found lower craving ratings with NAC. It rated the certainty of the evidence, meaning how sure the reviewers can be, as low. It concludes that NAC seems to reduce craving "but evidence is weak". It found no significant difference in withdrawal symptoms.

    The other, of nine trials with 623 people, found that NAC "did not significantly outperform placebo in reducing symptoms of craving". Leaving out one trial would have made that result significant. The authors report signs of publication bias and very high variation between trials, so they ask for cautious interpretation. They conclude: "Overall, our findings are contrary to those of prior meta-analyses, suggesting a limited impact of NAC on substance craving."

    Sources: Source [1]Source [2]

  • Reduces obsessive-compulsive disorder (OCD) symptoms when added to usual treatment Evidence rating: Limited

    People with OCD take it alongside their usual treatment, hoping for fewer obsessions and compulsions.

    Two reviews found some benefit with NAC, but one only at five to eight weeks, and the other found no significant difference in how many people responded to treatment.

    The evidence is small and mixed. A 2024 meta-analysis pooled six trials in people with moderate to severe OCD, in which NAC was added to existing treatment. It found a benefit on the main OCD rating scale only in the two trials that measured it at five to eight weeks. It found no significant difference at four weeks or less, at 12 weeks or more, or on the separate obsession and compulsion scores.

    The 2024 review describes its participants as adults, but in one of the six trials their average age was about 16. Its authors conclude that NAC "may serve as an effective adjunct treatment", but that whether the effect lasts with longer use remains unclear.

    A 2022 meta-analysis pooled ten NAC trials across OCD and related conditions, including hair-pulling and skin-picking disorders and trials in children. It found greater improvement in overall symptoms than with placebo. It found no significant difference in how many people responded to treatment, and warns that small-study effects might have influenced the result.

    Sources: Source [1]Source [2]

  • Reduces hair-pulling in trichotillomania Evidence rating: Limited

    People with trichotillomania, an urge to pull out their own hair, take it hoping to pull less.

    One trial in 50 adults found more responders with NAC, at moderate certainty, and one in 39 children found little to no difference; Cochrane found too little evidence to confirm or refute it.

    This rests on two small trials. A 2021 Cochrane review found one trial of NAC in 50 adults. After 12 weeks, 56% responded to NAC and 16% to placebo. The review rates this as moderate-certainty evidence of "probably greater treatment response".

    One trial in 39 children and adolescents found little to no difference (low certainty). The review concludes that there is "insufficient evidence from meta-analysis to confirm or refute the efficacy of any agent". It describes the adult result as preliminary evidence of a possible benefit.

    Sources: Source [1]

  • Improves schizophrenia symptoms when added to antipsychotic medication Evidence rating: Limited

    People with schizophrenia take it alongside antipsychotic medicine, hoping for fewer symptoms.

    Two reviews report a benefit for NAC added to antipsychotics, but both qualify it: two trials at low risk of bias conflict, and results vary widely between trials.

    Both cited reviews report a benefit for NAC added to antipsychotics, and both qualify it. A 2023 umbrella review by an international expert panel made a provisional recommendation for NAC added to antipsychotics, for negative symptoms and general symptoms. It found the most robust results in the longer trials.

    The 2023 panel also states that "two RCTs with low risk of bias have provided conflicting results", and that its results "should be interpreted with caution". It reports that positive results for negative symptoms were more frequent in trials from upper-middle-income countries than from high-income countries.

    A 2026 meta-analysis of six trials found greater symptom improvement with NAC than with placebo, with high variation between trials. Across all the anti-inflammatory treatments it studied, it concludes that current evidence "does not robustly support routine clinical use of these agents outside of research settings".

    Sources: Source [1]Source [2]

  • Improves depression in bipolar disorder when added to usual treatment Evidence rating: Limited

    People with bipolar disorder take it alongside their usual treatment, hoping it will lift their depression.

    A 2021 Cochrane review of three trials found no significant difference in response, and depression scores may have improved more with placebo, at very low certainty.

    Too little evidence, and it does not show a benefit. A 2021 Cochrane review found three trials that added NAC to ongoing treatment for 16 to 20 weeks. At three months, the number of people who responded did not differ significantly (two trials, 69 people). Depression scores may have improved more with placebo than with NAC (two trials, 58 people).

    The review’s abstract calls this evidence very low certainty, while its summary-of-findings table rates it low; this page records the lower.

    Sources: Source [1]

  • Supports immune function Evidence rating: Insufficient

    People take it hoping it will strengthen their immune system.

    ODS says NAC might improve immune function but that human research is very limited; in the trials it describes, in people with HIV, immune results were mixed.

    Too little human research to say. ODS states that NAC "might improve immune system function and suppress viral replication". In its section on HIV, it states that "clinical research on the effects of NAC supplementation on the immune system in humans is very limited".

    The trials ODS describes were in people with HIV. NAC increased the activity of natural killer cells, a type of immune cell, but did not affect CD4 or CD8 T-cell counts. Its effects on viral load were inconsistent.

    Sources: Source [1]

Which form the evidence used

Supplements are sold in several forms. This is what the sources on this page say about them — which form the research used, and any comparison those sources themselves made. Where they made none, this page does not rank the forms.

  • NAC taken by mouth, What the sources supportDetails

    The two NAC-only COPD meta-analyses cited below included only trials that gave NAC by mouth, and the Cochrane review of mucolytics in COPD included only oral treatment. No cited source compares brands, or capsules with tablets or powders. Source [1]Source [2]Source [3]

  • Inhaled or intravenous acetylcysteine (prescription drugs), Details

    NIH’s Office of Dietary Supplements (ODS) states that the inhaled, liquid form "is classified as a drug in the United States, not a dietary supplement" and is approved by FDA as a mucolytic, a medicine that loosens mucus. ODS adds that NAC given by mouth or into a vein also has FDA approval as a drug to treat acetaminophen (paracetamol) poisoning. These are medical uses under a doctor’s care, and none of the ratings below rests on them. Source [1]

Also documented elsewhere on this site

Other supplements we cover that document an interaction with the same thing. This is a pointer to what those pages say, not a statement about taking them together — we have no source reviewing these in combination.

Sources

  1. The efficacy of N-acetylcysteine in the management of chronic obstructive pulmonary disease: a systematic review and meta-analysis
    PeerJ, 2026 · Meta-analysis · Primary source
  2. The efficacy of N-acetylcysteine in chronic obstructive pulmonary disease patients: a meta-analysis
    Therapeutic Advances in Respiratory Disease, 2023 · Meta-analysis · Primary source
  3. Mucolytic agents versus placebo for chronic bronchitis or chronic obstructive pulmonary disease
    Cochrane Database of Systematic Reviews, 2019 · Systematic review · Primary source
  4. Effect of N-acetylcysteine on craving in substance use disorders (SUD): a meta-analysis of randomized controlled trials
    Frontiers in Pharmacology, 2024 · Meta-analysis · Primary source · Certainty: low
  5. N-acetylcysteine as a treatment for substance use cravings: A meta-analysis
    Addiction Biology, 2024 · Meta-analysis · Primary source
  6. The safety and efficacy of N-acetylcysteine as an augmentation in the treatment of obsessive-compulsive disorder in adults: a systematic review and meta-analysis of randomized clinical trials
    Frontiers in Psychiatry, 2024 · Meta-analysis · Primary source
  7. Mitochondrial modulators for obsessive-compulsive and related disorders: a systematic review and meta-analysis
    Translational Psychiatry, 2022 · Meta-analysis · Primary source
    Some of its authors disclose ties to industry.
  8. Pharmacotherapy for trichotillomania
    Cochrane Database of Systematic Reviews, 2021 · Systematic review · Primary source · Certainty: low
    Some of its authors disclose ties to industry.
  9. Adjunctive agents to antipsychotics in schizophrenia: a systematic umbrella review and recommendations for amino acids, hormonal therapies and anti-inflammatory drugs
    BMJ Mental Health, 2023 · Systematic review · Primary source
  10. Efficacy and safety of anti-inflammatory drug-assisted treatment of symptoms in patients with schizophrenia: a meta-analysis
    BMC Psychiatry, 2026 · Meta-analysis · Primary source
  11. Ketamine and other glutamate receptor modulators for depression in adults with bipolar disorder
    Cochrane Database of Systematic Reviews, 2021 · Systematic review · Primary source · Certainty: very low
    Some of its authors disclose ties to industry.
  12. Dietary Supplements for Immune Function and Infectious Diseases: Fact Sheet for Health Professionals
    NIH Office of Dietary Supplements, 2025 · Health authority summary · Primary source
  13. Acetylcysteine Solution, USP 10% and 20% (Hospira): prescribing information
    DailyMed, U.S. National Library of Medicine, 2018 · Health authority summary · Primary source
  14. Acetadote (acetylcysteine) injection, for intravenous use: prescribing information
    U.S. Food and Drug Administration (Drugs@FDA, NDA 021539), 2025 · Health authority summary · Primary source
  15. Acetylcysteine and carbocysteine for acute upper and lower respiratory tract infections in paediatric patients without chronic broncho-pulmonary disease
    Cochrane Database of Systematic Reviews, 2013 · Systematic review · Primary source
  16. Guidance for Industry: Policy Regarding N-acetyl-L-cysteine
    U.S. Food and Drug Administration, 2022 · Health authority summary · Primary source
  17. FDA Releases Final Guidance on Enforcement Discretion for Certain NAC Products
    U.S. Food and Drug Administration, Human Foods Program, 2023 · Health authority summary · Primary source

Page history

Show all 3 changes to this page
  • — Rewritten to the content style guideline; ratings and sources unchanged.
  • — Published. The claims, the FDA regulatory history, the safety section and every source passed the site's source and wording reviews over two revision rounds. The owner's funding and disclosure decisions are recorded in docs/08-open-decisions.md.
  • — First drafted. COPD flare-ups, substance use cravings, OCD, trichotillomania, schizophrenia and bipolar depression rated limited; immune function rated insufficient. US regulatory status added to the safety section from FDA’s own documents.