What are N-acetylcysteine’s main drawbacks?

    Written by:
    Bill Willis, Katie Jantz

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    by:

    Nick Milazzo, Dmitri Barvinok
    Last Updated: May 16, 2025

    N-acetylcysteine can cause side effects such as nausea, vomiting, and diarrhea and may have an unpleasant odor due to its sulfur content. Inhalation can lead to cough and bronchospasm, and excessive doses can result in serious health issues, including hemolysis, thrombocytopenia, kidney failure, and potentially death.

    NAC is safe and effective at reasonable doses through oral supplementation. The most common side effects from oral NAC include nausea, vomiting, and diarrhea.[1][2] Due to the sulfur content of NAC, supplements can have an unpleasant rotten-egg odor.[1] When inhaled, NAC may cause cough and bronchospasm (constriction of the airways).[3]

    NAC toxicity mostly occurs in clinical settings, with one case of overdose occurring due to an error in the preparation of an IV solution. An excessive dose of NAC in a short time period can cause red blood cell breakdown (hemolysis), low blood platelet count (thrombocytopenia), kidney failure, and possibly death.[4]