NAC Evidence: Lung Conditions, Psychiatric Research, Fertility and Liver
What reviews and trials report for NAC in chronic bronchitis and COPD, OCD and other psychiatric conditions, PCOS, male fertility and liver failure, rated by strength of evidence.
Content last updated . This page has not been medically reviewed.
Read this first
NAC is not a replacement for treatment from your clinician. If you have a lung condition, a mental health condition, fertility concerns or liver disease, do not stop or change a prescribed medicine to try NAC. If you are in crisis or thinking of harming yourself, call or text 988 (US) or call 911. For acetaminophen overdose, the only safe path is emergency care; see NAC: FDA Status and Acetaminophen Overdose.The short answer
NAC (N-acetylcysteine, an acetylated form of the amino acid cysteine; see Cysteine, Cystine and Glutathione Precursor Claims) has been studied in many conditions. The most consistent signal we read is for fewer flare-ups of chronic bronchitis and COPD. Results for psychiatric conditions are mixed, fertility results are mostly lab measures, and a review of non-acetaminophen liver failure did not show a survival benefit. Amounts below are study amounts, not advice.Evidence labels used here
"Promising but limited" means trials suggest a benefit but they are few, small or short. "Mixed" means trials disagree. "No good evidence of benefit" means a review found no clear effect on the main outcome. A lab measure (for example hormones or sperm counts) is not the same as a pregnancy or live birth.What the research found
| Condition | What the source found | Strength of evidence |
|---|---|---|
| Chronic bronchitis and COPD flare-ups | A 2024 meta-analysis of 20 studies found fewer exacerbations than placebo in COPD (rate ratio 0.76). [1] A 2015 meta-analysis of 13 studies (4,155 people) found relative risk 0.75. [2] | Promising but limited |
| OCD, added to usual medicine | A 2024 meta-analysis of 6 trials (195 people) found a benefit in a five-to-eight-week window (p = 0.05) but not for shorter or longer periods. [3] A 16-week trial in 40 adults with treatment-resistant OCD (3,000 mg daily, study amount) found no difference from placebo. [4] | Mixed |
| Skin-picking disorder | One trial of 66 adults (1,200 to 3,000 mg a day for 12 weeks, study amounts) reported significant improvement. [5] | Promising but limited (single trial) |
| Alcohol use disorder and PTSD | A 2026 review of 7 trials (566 people) did not find consistent benefit over placebo in broad groups. [6] | Mixed |
| PCOS | A 2025 meta-analysis of 22 studies (follicle growth, endometrial thickness and hormones) reported higher progesterone, but no difference in estradiol, SHBG or FSH. [7] A 2023 meta-analysis of 11 trials (869 women) found lower fasting blood glucose than metformin or placebo. [8] | Promising but limited; lab measures only |
| Male infertility (semen quality) | A 2025 meta-analysis of seven trials (three tested NAC against placebo) reported better sperm motility, concentration and shape. [9] A second meta-analysis of 5 studies reported no side effects in the included studies. [10] | Promising but limited; lab measures only |
| Non-acetaminophen acute liver failure | A 2024 meta-analysis of 4 trials of intravenous NAC could not show better survival. [11] | No good evidence of benefit |
What these results do not tell you
- Lung conditions: neither review is a guide to choosing a product or an amount. Talk to your clinician about COPD care.
- Psychiatric research: the OCD review authors call for more multi-center trials over longer periods. [3]
- PCOS: these studies measured hormones, glucose and follicle markers, not pregnancy or live birth. Two authors of the 2025 review were employed by a wellness company. [7] A 2015 trial of NAC added to metformin and clomiphene for ovulation induction in PCOS has been retracted; the PubMed record we read gives no reason. [12]
- Fertility: the abstracts we read report semen measurements. Proper evidence not found for pregnancy or live-birth outcomes (we searched PubMed for NAC infertility reviews and trials).
- Liver: acetaminophen overdose, where NAC is an established hospital antidote, is different from other causes of liver failure. [13]
Related pages
See N-Acetylcysteine (NAC), Glycine and N-Acetylcysteine (GlyNAC) in Aging Research, Antioxidant Evidence by Use and Polycystic Ovary Syndrome (PCOS).Frequently asked questions
Does NAC help COPD?
Two meta-analyses reported fewer flare-ups than placebo. [1] [2] It does not replace COPD treatment from your clinician.
Does NAC help OCD?
Results are mixed: a meta-analysis found a benefit in one time window [3], while a 16-week trial found no difference. [4]
Does NAC help PCOS or fertility?
Meta-analyses report changes in hormones, glucose and semen measures. [7] [8] [9] Pregnancy outcomes were not shown in the abstracts we read.
Does NAC help liver disease?
For non-acetaminophen acute liver failure, a meta-analysis could not show a survival benefit. [11]
Is NAC safe?
A meta-analysis of COPD trials described it as well tolerated [2], but abdominal pain was more common than placebo in one trial. [4] Ask a clinician if you are pregnant or have a health condition.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety and who should ask first
NAC can cause side effects such as abdominal pain in some trials [4]; see the safety section of the NAC FDA-status page. Talk to a clinician or pharmacist before use if you are pregnant or breastfeeding, have asthma, liver or kidney disease, take psychiatric or other regular medicines, or have surgery planned. For children, NAC should only be used under a clinician's direction. See Medication Interactions and Quality Testing and Certifications.
References
- Papi A, et al. N-acetylcysteine Treatment in Chronic Obstructive Pulmonary Disease (COPD) and Chronic Bronchitis/Pre-COPD: distinct meta-analyses. Arch Bronconeumol 2024. PubMed record PMID 38555190. Read 2026-10-23.
- Cazzola M, et al. Influence of N-acetylcysteine on chronic bronchitis or COPD exacerbations: a meta-analysis. Eur Respir Rev 2015. PubMed record PMID 26324807. Read 2026-10-23.
- Eghdami S, et al. 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. Front Psychiatry 2024. PubMed record PMID 39376972. Read 2026-10-23.
- Costa DLC, et al. Randomized, double-blind, placebo-controlled trial of N-acetylcysteine augmentation for treatment-resistant obsessive-compulsive disorder. J Clin Psychiatry 2017. PubMed record PMID 28617566. Read 2026-10-23.
- Grant JE, et al. N-Acetylcysteine in the Treatment of Excoriation Disorder: a randomized clinical trial. JAMA Psychiatry 2016. PubMed record PMID 27007062. Read 2026-10-23.
- Ahmed MAE, et al. N-acetylcysteine for patients with alcohol use disorder, post-traumatic stress disorder, and their co-occurrence: a systematic review of placebo-controlled randomized trials. BMC Psychiatry 2026. PubMed record PMID 42115982. Read 2026-10-23.
- Viña I, et al. Efficacy of N-Acetylcysteine in Polycystic Ovary Syndrome: systematic review and meta-analysis. Nutrients 2025. PubMed record PMID 39861414. Read 2026-10-23.
- Liu J, et al. The effects of N-acetylcysteine supplement on metabolic parameters in women with polycystic ovary syndrome: a systematic review and meta-analysis. Front Nutr 2023. PubMed record PMID 37841396. Read 2026-10-23.
- Ma X, et al. Meta-analysis of the efficacy and safety of L-carnitine and N-acetylcysteine monotherapy for male idiopathic infertility. Rev Int Androl 2025. PubMed record PMID 40350672. Read 2026-10-23.
- Syarif S, et al. NAC to improve seminal parameters and analysis of its safety: a systematic review and meta-analysis of randomized controlled trials. Arch Ital Urol Androl 2025. PubMed record PMID 40126496. Read 2026-10-23.
- Orban C, et al. No Significant Beneficial Effects of Intravenous N-Acetylcysteine on Patient Outcome in Non-Paracetamol Acute Liver Failure: a meta-analysis of randomized controlled trials. Biomedicines 2024. PubMed record PMID 39062036. Read 2026-10-23.
- Statement of Retraction: The adjuvant effect of metformin and N-acetylcysteine to clomiphene citrate in induction of ovulation in patients with Polycystic Ovary Syndrome. Gynecol Endocrinol 2025. PubMed record PMID 41391099. Read 2026-10-23.
- MedlinePlus Medical Encyclopedia: Acetaminophen overdose (U.S. National Library of Medicine), review date 8 January 2025. Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.