N-Acetyl Cysteine (NAC)

Medically Reviewed by Melinda Ratini, MS, DO on March 31, 2022
2 min read

N-acetyl cysteine (NAC) is used by the body to build antioxidants. Antioxidants are vitamins, minerals, and other nutrients that protect and repair cells from damage.

You can get NAC as a supplement or a prescription drug.

As a prescription drug, doctors use NAC to treat acetaminophen overdose. It may also help break up mucus in people with some lung diseases, like chronic bronchitis.

As a supplement, some people use NAC to try to protect the liver. There's evidence it can help prevent kidney or neurologic damage caused by some drugs.

NAC might help prevent colon cancer in people with some types of colon polyps, but more research is needed to be sure. NAC does not seem to reduce the risk of lung cancer or head and neck cancer.

There's mixed evidence about whether NAC helps with other conditions, like infertility, the flu, cystic fibrosis, liver disease, angina, HIV, high cholesterol, and some eye conditions. More research is needed.

Optimal doses of NAC as a supplement have not been set for any condition. Quality and active ingredients in supplements may vary widely from maker to maker. This makes it very hard to set a standard dose.

There are standard doses for prescription uses of NAC. These depend on the condition that is being treated. Ask your doctor for advice.

NAC cannot be found in foods.

Tell your doctor about any supplements you're taking, even if they're natural. That way, your doctor can check on any potential side effects or interactions with medications.

Side effects. Some of the side effects that may be caused by NAC include:

Risks. If you have asthma or bleeding problems, your doctor may tell you to avoid NAC.  You will likely be told to stop NAC 2 weeks before any elective surgery.

If you're pregnant or breastfeeding, you must check with a doctor before using NAC supplements.

Interactions. If you take any medicines regularly, talk to your doctor before you start using NAC supplements. They could interact with nitroglycerin, blood thinners, and certain blood pressure medicines.

Dietary supplements are not regulated by the FDA in the same way that drugs are.  The FDA does not review these supplements for safety or efficacy before they hit the market.