Supplement
N-acetylcysteine is a modified form of the amino acid cysteine that the body uses to build glutathione, a key antioxidant, and it also thins mucus. People mostly look at it for chronic obstructive pulmonary disease (COPD), and a meta-analysis of oral use found bronchitis symptoms improved, though the evidence there is moderate. Another COPD outcome, chronic bronchitis, showed no clear difference, and the studies behind these findings were small.
Sources: PMID 31598901
- Updated
- How we grade
- 34 studies cited
- Best evidence
- Grade B
- Conditions studied
- 31
- Outcomes
- 72
- Graded outcomes
- 0549
Evidence by condition
- Strong
- Moderate
- Limited
- Very limited
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Bronchitis Symptoms Small Improvement | Improves (the measure goes down) | Small effect | 1 study | 968 people | ||
Studies that measured bronchitis symptoms | ||||||
| Chronic Bronchitis No effect | NoneNo effect | 1,564 people | ||||
| COPD Symptoms | Improves (the measure goes down) | 5 studies | 905 people | |||
Studies that measured copd symptoms
| ||||||
| Neutrophil Activity | Improves (the measure goes up) | 1 study | 50 people | |||
Studies that measured neutrophil activity | ||||||
| Glutathione (GSH) | Improves (the measure goes up) | 645 people | ||||
| Lung Function | Improves (the measure goes up) | 50 people | ||||
Acute Bronchitis
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Bronchitis Symptoms Small Improvement | Improves (the measure goes down) | Small effect | 1 study | 968 people | ||
Studies that measured bronchitis symptoms | ||||||
| Chronic Bronchitis | Improves (the measure goes up) | 1,564 people | ||||
Acute Bronchitis
- Bronchitis Symptoms: improves
- Chronic Bronchitis: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Bronchitis Symptoms Small Improvement | Improves (the measure goes down) | Small effect | 1 study | 968 people | ||
Studies that measured bronchitis symptoms | ||||||
| Chronic Bronchitis | Improves (the measure goes up) | 1,564 people | ||||
Autism Spectrum Disorder (ASD)
- Autism Symptoms: improves
- Irritability: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Autism Symptoms Small Improvement | Improves (the measure goes down) | Small effect | 56 people | |||
| Irritability | Improves (the measure goes down) | 2 studies | 56 people | |||
Polycystic Ovary Syndrome (PCOS)
- Blood glucose: improves
- Body Mass Index (BMI): improves
- Testosterone: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Blood glucose Small Improvement | Improves (the measure goes down) | Small effect | 869 people | |||
| Body Mass Index (BMI) | Improves (the measure goes down) | 1 study | 869 people | |||
Studies that measured body mass index (bmi) | ||||||
| Testosterone | Improves (the measure goes up) | 1 study | 725 people | |||
| Endometrial Thickness | Improves (the measure goes up) | 2,663 people | ||||
| Estrogen | Changes; see studies | 2,160 people | ||||
| Follicle-Stimulating Hormone | Improves (the measure goes up) | 610 people | ||||
| High-density lipoprotein (HDL) | Improves (the measure goes up) | 235 people | ||||
| Low-density lipoprotein (LDL) | Improves (the measure goes down) | 235 people | ||||
| Luteinizing Hormone | Improves (the measure goes up) | 990 people | ||||
| Progesterone | Improves (the measure goes up) | 1,842 people | ||||
| Sex Hormone Binding Globulin | Improves (the measure goes up) | 414 people | ||||
| Total cholesterol | Improves (the measure goes down) | 235 people | ||||
| Triglycerides | Improves (the measure goes down) | 235 people | ||||
| Weight | Improves (the measure goes down) | 530 people | ||||
Immune Health
- COPD Symptoms: improves
- Neutrophil Activity: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| COPD Symptoms Small Improvement | Improves (the measure goes down) | Small effect | 5 studies | 20 people | ||
Studies that measured copd symptoms
| ||||||
| Neutrophil Activity | Improves (the measure goes up) | 1 study | 50 people | |||
Studies that measured neutrophil activity | ||||||
Substance Use Disorder
- Cocaine Addiction Symptoms: improves
- Tobacco Addiction Symptoms: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Cocaine Addiction Symptoms Small Improvement | Improves (the measure goes down) | Small effect | 2 studies | 245 people | ||
Studies that measured cocaine addiction symptoms | ||||||
| Tobacco Addiction Symptoms | Improves (the measure goes down) | 1 study | 245 people | |||
Studies that measured tobacco addiction symptoms | ||||||
Metabolic Health
- Anaerobic Capacity: improves
- Mineral Bioaccumulation: improves
- Anti-Oxidant Enzyme Profile: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Anaerobic Capacity Small Improvement | Improves (the measure goes up) | Small effect | 1 study | 12 people | ||
Studies that measured anaerobic capacity | ||||||
| Mineral Bioaccumulation | Improves (the measure goes up) | 1 study | 171 people | |||
Studies that measured mineral bioaccumulation | ||||||
| Anti-Oxidant Enzyme Profile | Improves (the measure goes up) | 171 people | ||||
Soccer Performance
- Anaerobic Capacity: improves
- Power Output: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Anaerobic Capacity Small Improvement | Improves (the measure goes up) | Small effect | 1 study | 12 people | ||
Studies that measured anaerobic capacity | ||||||
| Power Output | Improves (the measure goes up) | 12 people | ||||
Surgical Recovery
- All-Cause Mortality
- Kidney Function: improves
- Length of hospitalization: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| All-Cause Mortality No effect | NoneNo effect | 1 study | 1,737 people | |||
| Kidney Function | Improves (the measure goes up) | 1 study | 1,711 people | |||
| Length of hospitalization | Improves (the measure goes down) | 1 study | 1,512 people | |||
Studies that measured length of hospitalization | ||||||
| Liver Enzymes | Changes; see studies | 1 study | 448 people | |||
| Heart Arrhythmias | Changes; see studies | 886 people | ||||
| Heart Attack Risk | Changes; see studies | 1,178 people | ||||
Chronic pain
- Pain
- Quality of Life: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Pain No effect | NoneNo effect | 1 study | 286 people | |||
| Quality of Life | Improves (the measure goes up) | 198 people | ||||
Acute Liver Failure
- All-Cause Mortality
- Length of hospitalization: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| All-Cause Mortality No effect | NoneNo effect | 1 study | 469 people | |||
| Length of hospitalization | Improves (the measure goes down) | 1 study | 469 people | |||
Studies that measured length of hospitalization | ||||||
Bipolar Disorder
- Anxiety Symptoms
- Depression Symptoms: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Anxiety Symptoms No effect | NoneNo effect | 315 people | ||||
| Depression Symptoms | Improves (the measure goes down) | 4 studies | 335 people |
Depression
- Anxiety Symptoms
- Depression Symptoms: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Anxiety Symptoms No effect | NoneNo effect | 319 people | ||||
| Depression Symptoms | Improves (the measure goes down) | 4 studies | 574 people |
Major Depressive Disorder (MDD)
- Anxiety Symptoms
- Depression Symptoms: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Anxiety Symptoms No effect | NoneNo effect | 315 people | ||||
| Depression Symptoms | Improves (the measure goes down) | 4 studies | 579 people |
Schizophrenia
- Processing Speed
- Schizophrenia symptoms: improves
- Working Memory: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Processing Speed No effect | NoneNo effect | 136 people | ||||
| Schizophrenia symptoms | Improves (the measure goes down) | 1 study | 354 people | |||
| Working Memory | Improves (the measure goes up) | 136 people |
Trichotillomania (Hair Pulling)
- Anxiety Symptoms
- Depression Symptoms: improves
- Trichotillomania Symptoms: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Anxiety Symptoms No effect | NoneNo effect | 50 people | ||||
| Depression Symptoms | Improves (the measure goes down) | 4 studies | 50 people | |||
| Trichotillomania Symptoms | Improves (the measure goes down) | 1 study | 50 people | |||
| Subjective Well-Being | Improves (the measure goes up) | 50 people |
Hearing Loss
- Hearing Loss: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Hearing Loss | Improves (the measure goes up) | 3 studies | 278 people |
Obesity
- Hearing Loss: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Hearing Loss | Improves (the measure goes up) | 3 studies | 278 people |
Overweight
- Hearing Loss: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Hearing Loss | Improves (the measure goes up) | 3 studies | 278 people |
Cocaine Abuse
- Cocaine Addiction Symptoms: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Cocaine Addiction Symptoms | Improves (the measure goes down) | 2 studies | 13 people |
Cannabis Use Disorder
- Marijuana Addiction: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Marijuana Addiction | Improves (the measure goes up) | 1 study | 24 people |
Cardiovascular Disease
- Urinary NOx: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Urinary NOx | Improves (the measure goes up) | 1 study | 8 people |
General Cardiovascular Health
- Urinary NOx: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Urinary NOx | Improves (the measure goes up) | 1 study | 8 people |
General Liver Health
- Liver Enzymes: changes; see studies
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Liver Enzymes | Changes; see studies | 1 study | 448 people |
H. Pylori Infection
- Helicobacter Pylori Infection Signs: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Helicobacter Pylori Infection Signs | Improves (the measure goes up) | 1 study | 1,167 people |
Kidney Health
- Kidney Function: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Kidney Function | Improves (the measure goes up) | 1 study | 21,580 people |
Obsessive-Compulsive disorder (OCD)
- OCD Symptoms: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| OCD Symptoms | Improves (the measure goes down) | 1 study | 48 people |
Tobacco Use Disorder
- Tobacco Addiction Symptoms: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Tobacco Addiction Symptoms | Improves (the measure goes down) | 1 study | 29 people |
H. Pylori Infection
- Helicobacter Pylori Infection Signs: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Helicobacter Pylori Infection Signs | Improves (the measure goes up) | 1 study | 1,167 people |
Acne
- Acne Symptoms: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Acne Symptoms | Improves (the measure goes down) | 56 people |
What the published studies found
3 automated readings
LDL cholesterol
The studies read are too weak to tell whether N-Acetylcysteine changes LDL cholesterol. The evidence is very weak.
2 studies counted of 9 read: 2 trials (134 people in the trials).
- Randomised trial, 2026; 60 people; women with endometriosis undergoing ICSI: no clear difference.
with no significant change in LDL
The Effect of N-Acetyl Cysteine on Serum Lipid Profile and Heavy Metals in Women With Endometriosis Undergoing ICSI: A Randomized Controlled Trial - Randomised trial, 2022; 74 people: no clear difference.
There were no significant changes in morning stiffness, DAS-28, ESR, hs-CRP, MDA, TAC, GPx activity, …
Effects of N-acetylcysteine supplementation on disease activity, oxidative stress, and inflammatory and metabolic parameters in rheumatoid arthritis patients: a randomized double-blind placebo-controlled trial
- Randomised trial, 2026; 60 people; women with endometriosis undergoing ICSI: no clear difference.
Cardiovascular events
Mixed or unclear: two readings of the studies disagreed. One reading found an improvement for cardiovascular events, the other mixed results. The question is open.
6 studies counted of 9 read: 4 reviews and 1 trial (134 people in the trials).
- Meta-analysis, 2024; 19 studies, 3,718 people; patients undergoing coronary catheterization or cardiac surgery: no clear difference (the review the verdict rests on).
occurrence of secondary outcomes was not significantly reduced
N-Acetylcysteine to Reduce Mortality for Patients Requiring Cardiac Catheterization or Cardiac Surgery: A Systematic Review and Meta-analysis - Meta-analysis, 2021; 9 studies, 1,419 people; patients with ST segment elevation myocardial infarction: improves.
occurrence of major adverse cardiovascular events (MACE) [RR = 0.63
The Clinical Efficacy of N-Acetylcysteine in the Treatment of ST Segment Elevation Myocardial Infarction - Meta-analysis, 2021; 15 studies, 768 people; people with chronic kidney disease: improves.
NAC did reduce cardiovascular events among people with CKD
N-acetylcysteine for chronic kidney disease: a systematic review and meta-analysis - Systematic review, 2012; 56 studies: improves. Antioxidant therapy in hemodialysis patients: a systematic review
- Study, 2007: improves. It is important to lower homocysteine in dialysis patients
- Randomised trial, 2003; 134 people; hemodialysis patients with end-stage renal failure: improves.
relative risk, 0.60 [95% CI, 0.38 to 0.95], P=0.03
The antioxidant acetylcysteine reduces cardiovascular events in patients with end-stage renal failure: a randomized, controlled trial
- Meta-analysis, 2024; 19 studies, 3,718 people; patients undergoing coronary catheterization or cardiac surgery: no clear difference (the review the verdict rests on).
Memory
The studies disagree. The best available review (2022, 6 studies) did not settle it for memory, while 3 of the 6 studies read found an improvement. The evidence is very weak.
6 studies counted of 11 read: 3 reviews and 3 trials (117 people in the trials).
- Meta-analysis, 2022; 6 studies; patients with schizophrenia: unclear: evidence too weak to tell (the review the verdict rests on). Antipsychotic Augmentation With N-Acetylcysteine for Patients With Schizophrenia
- Meta-analysis, 2020; 7 studies, 440 people; patients with schizophrenia: improves.
working memory improved with N-acetylcysteine supplementation
Meta-analysis of randomised controlled trials with N-acetylcysteine in the treatment of schizophrenia - Meta-analysis, 2019; 25 studies, 1,951 people; patients with schizophrenia: improves.
N-acetyl cysteine (NAC) had a significant effect on working memory ( P-value for interaction = …
Effect of N-methyl-D-aspartate-receptor-enhancing agents on cognition in patients with schizophrenia: A systematic review and meta-analysis of double-blind randomised controlled trials - Randomised trial, 2026; 59 people; patients with mild cognitive impairment: no clear difference.
no significant differences between N-acetylcysteine and placebo
Efficacy and safety of N-acetylcysteine in patients with mild cognitive impairment undergoing exercise-based cardiac rehabilitation program: a randomized controlled trial - Randomised trial, 2017; 58 people: improves.
significantly higher working memory performance at week 24
Cognitive effects of adjunctive N-acetyl cysteine in psychosis - Randomised trial, 2012: no clear difference.
failed to find changes in cognitive function
Effects of N-acetyl cysteine on cognitive function in bipolar disorder
Key findings
- Bronchitis SymptomsImproves (the measure goes down)
- Autism SymptomsImproves (the measure goes down)
- Blood glucoseImproves (the measure goes down)
Shop the evidence-backed picks
Third-party tested N-Acetylcysteine products, in the forms the graded studies used where we can match them.
- Grade B
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Studies cited
34 studies from PubMed
- Safety and tolerability of N-acetylcysteine in cocaine-dependent individuals
- The administration of N-acetylcysteine reduces oxidative stress and regulates glutathione metabolism in the blood cells of workers exposed to lead
- N-Acetylcysteine Attenuates Fatigue Following Repeated-Bouts of Intermittent Exercise: Practical Implications for Tournament Situations
- N-acetylcysteine, a glutamate modulator, in the treatment of trichotillomania: a double-blind, placebo-controlled study
- New developments in the treatment of COPD: comparing the effects of inhaled corticosteroids and N-acetylcysteine
- Induced sputum of patients with chronic obstructive pulmonary disease (COPD) contains adhesion-promoting, therapy-sensitive factors
- N-acetylcysteine add-on treatment in refractory obsessive-compulsive disorder: a randomized, double-blind, placebo-controlled trial
- Systematic review and meta-analysis of the efficacy of N-acetylcysteine in the treatment of acute exacerbation of chronic obstructive pulmonary disease.
- Effects of N-acetylcysteine on outcomes in chronic obstructive pulmonary disease (Bronchitis Randomized on NAC Cost-Utility Study, BRONCUS): a randomised placebo-controlled trial
- Long-term oral n-acetylcysteine reduces exhaled hydrogen peroxide in stable COPD
- The efficacy of -acetylcysteine in chronic obstructive pulmonary disease patients: a meta-analysis.
- Effect of Orally Administered N-Acetylcysteine on Chronic Bronchitis: A Meta-analysis.
- A randomized controlled pilot trial of oral N-acetylcysteine in children with autism
- A randomized double blind placebo controlled clinical trial of N-Acetylcysteine added to risperidone for treating autistic disorders
- N-Acetylcysteine (NAC) inhibits renal nitrite and nitrate reabsorption in healthy subjects and in patients undergoing cardiac surgery: risk of nitric oxide (NO) bioavailability loss by NAC?
- The role of cystine-glutamate exchange in nicotine dependence in rats and humans
- N-acetylcysteine (NAC) in young marijuana users: an open-label pilot study
- N-Acetylcysteine in depressive symptoms and functionality: a systematic review and meta-analysis.
- N-acetylcysteine in the treatment of craving in substance use disorders: Systematic review and meta-analysis.
- Meta-analysis of randomised controlled trials with -acetylcysteine in the treatment of schizophrenia.
- Meta-analytic Techniques to Assess the Association Between N-acetylcysteine and Acute Kidney Injury After Contrast Administration: A Systematic Review and Meta-analysis.
- The efficacy of adjuvant N acetyl cysteine for the eradication of H pylori infections: A systematic review and meta-analysis of randomized clinical trials.
- N-acetylcysteine in the Donor, Recipient, or Both Donor and Recipient in Liver Transplantation: A Systematic Review With Meta-analysis and Trial Sequential Analysis.
- N-acetylcysteine use among patients undergoing cardiac surgery: A systematic review and meta-analysis of randomized trials.
- The effect of N-acetylcysteine on bipolar depression: a systematic review and meta-analysis of randomized controlled trials.
- N-acetylcysteine as an adjunctive treatment for bipolar depression: A systematic review and meta-analysis of randomized controlled trials.
- N-acetylcysteine as an adjunctive treatment for bipolar depression and major depressive disorder: a systematic review and meta-analysis of double-blind, randomized placebo-controlled trials.
- Efficacy and Safety of N-Acetylcysteine for the Management of Chronic Pain in Adults: A Systematic Review and Meta-Analysis.
- The effects of N-acetylcysteine on ovulation and sex hormones profile in women with polycystic ovary syndrome: a systematic review and meta-analysis
- The effects of N-acetylcysteine supplement on metabolic parameters in women with polycystic ovary syndrome: a systematic review and meta-analysis.
- A systematic review and meta-analysis of the efficacy and safety of N-acetylcysteine in preventing aminoglycoside-induced ototoxicity: implications for the treatment of multidrug-resistant TB.
- Effect of N-acetyl-cysteine in prevention of noise-induced hearing loss: a systematic review and meta-analysis of randomized controlled trials.
- Effect of N-acetyl-cysteine treatment on sensorineural hearing loss: a meta-analysis.
- No Significant Beneficial Effects of Intravenous N-Acetylcysteine on Patient Outcome in Non-Paracetamol Acute Liver Failure: A Meta-Analysis of Randomized Controlled Trials.