N-acetylcysteine
N-acetylcysteine 600 mg capsules or effervescent tablets, pharmaceutical grade. In Mexico it is sold as a drug (Fluimucil and generics), which is the preferable supply route.
Moderate
Some good studies, not many repeats
Moderate-certainty Cochrane evidence (38 trials, 10,377 people) but in a clinical population only, and the Cochrane authors flag that newer trials show smaller effects than older ones — consistent with publication bias. The 2024 Nature Communications RCT in mild-to-moderate COPD missed its primary endpoint. NOT a supplement for a healthy Umbral user whose resp_rate_bpm or breathing_disturbance_index has drifted: that pattern is a reason to see a doctor about sleep apnoea or asthma, not to take a mucolytic.
For people with chronic bronchitis or COPD it means fewer flare-ups and fewer sick days. In milder cases a large two-year study found no benefit. This is a long-term treatment for a diagnosed condition, not a response to a wearable reading.
In chronic bronchitis/COPD, mucolytics made people more likely to stay exacerbation-free (Peto OR 1.73, 95% CI 1.56-1.91; NNT ~8 over 9 months) and cut 0.43 disability days per person per month (95% CI -0.56 to -0.30) — but in mild-to-moderate COPD a 968-person 2-year trial was null on total exacerbations (RR 0.90, 95% CI 0.80-1.02).
Cleaves disulphide bonds in mucus glycoproteins, lowering sputum viscosity, and replenishes the glutathione precursor pool in the airway epithelium.
People with a diagnosis of chronic bronchitis or COPD with chronic sputum production, not on inhaled corticosteroids. Healthy users with a normal spirometry have no trial evidence at all.
What to buy
- ✓N-acetylcysteine 600 mg capsules or effervescent tablets, pharmaceutical grade. In Mexico it is sold as a drug (Fluimucil and generics), which is the preferable supply route.
- ✓600 mg twice daily (1200 mg/day) is the dose used in the large COPD trials. Lower 'antioxidant' doses have no respiratory outcome data.
- ✓Third-party tested (USP, NSF, Informed Sport)
- ✕Proprietary blends that hide the dose per ingredient
- ✕Unstandardised extracts with no active-compound percentage
- · Nausea, vomiting and diarrhoea are the most common oral adverse effects.
- · Can trigger bronchospasm in some people with asthma or hyperreactive airways.
- · Rare anaphylactoid/hypersensitivity reactions, mainly with intravenous use.
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600 mg is the unit every trial used, twice a day. The most-bought NAC on Amazon and the cheapest per gram.
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Twenty-one thousand ratings, the most-reviewed NAC here. The selenium and molybdenum support the same detox pathway rather than muddying the test.
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The highest-rated of the three and hypoallergenic. In Mexico NAC is sold as a drug (Fluimucil and generics), which is the better supply route if you are there.
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See all on AmazonEvery result, next to the line that means no effect
Each diamond is a study's best estimate. The thin line shows how sure the study was: the shorter the line, the more certain the result.
- Staying exacerbation-free (COPD/chronic bronchitis)Peto odds ratio · Poole 2019, Cochrane CD001287.pub6+1.73+1.56 … +1.91
- Days of disabilitydays per person per month · Poole 2019, Cochrane CD001287.pub6−0.43−0.56 … −0.30
- Total exacerbation rate, mild-moderate COPDrate ratio (null) · Nature Communications 2024 RCT+0.90+0.80 … +1.02
- Moderate-severe exacerbations, mild-moderate COPDrate ratio · Nature Communications 2024 RCT (secondary endpoint)+0.76+0.64 … +0.90
Each unit gets its own scale, so numbers are never mixed on one line. When a study gave no range, we leave it blank instead of inventing one.
3 studies over 10 years
The studies
- 1.Mucolytic agents versus placebo for chronic bronchitis or chronic obstructive pulmonary diseaseCochrane Database of Systematic Reviews · 2019 · meta-analysis · 38 experiments · n = 10,377
Moderate-certainty evidence for fewer exacerbations (Peto OR 1.73, 95% CI 1.56-1.91) and 0.43 fewer disability days/person/month, with no excess adverse events (OR 0.84, 95% CI 0.74-0.94); authors caution newer trials show smaller effects.
- 2.Effect of high-dose N-acetylcysteine on exacerbations and lung function in patients with mild-to-moderate COPD: a double-blind, parallel group, multicentre randomised clinical trialNature Communications · 2024 · rct · 1 experiments · n = 968
600 mg twice daily for 2 years did not reduce total exacerbations (0.65 vs 0.72/patient-year; RR 0.90, 95% CI 0.80-1.02) or improve FEV1 (16 mL, 95% CI -69 to 100).
- 3.Twice daily N-acetylcysteine 600 mg for exacerbations of chronic obstructive pulmonary disease (PANTHEON): a randomised, double-blind placebo-controlled trialThe Lancet Respiratory Medicine · 2014 · rct · 1 experiments · n = 1,006
The pivotal Chinese multicentre trial that established 1200 mg/day NAC for exacerbation reduction in moderate-to-severe COPD; note the population is clinical, not healthy adults.
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