Summary
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What is N-Acetyl Cysteine (NAC)?
NAC is a synthetic compound that is converted to glutathione in the body (see What It Is). -
Do NAC supplements work?
NAC has a wide variety of uses — although not all are well-proven. As a prescription drug it is used to treat acetaminophen poisoning (to protect the liver), but general claims of "liver protection" are not well established. It has also been used in inhaled form to loosen mucus in people with cystic fibrosis, and orally it may help with symptoms of flu, chronic bronchitis and COPD symptoms, but evidence is weak for its purported ability to thin mucus during a cold and general claims of "immune support." (See What It Does). -
What did CL's tests of NAC find?
ConsumerLab found the cost to obtain 600 mg of NAC ranged over 15-fold from just 4 cents to as much as 63 cents. A single dose of NAC ranged from 500 to 1,000 mg. Quality-wise, all products contained their claimed amounts of NAC, although one also contained a significant amount of sodium. (See What CL Found and use the Results table to compare the amounts of NAC and sodium in products). 
Best NAC Supplement?
ConsumerLab selected Top Picks for NAC as a powder, capsule, and tablet based on quality, value, and other features.-
What to look for in NAC supplements?
NAC is always in the "free form" so if you see this on a label, it's nothing you should pay more for. Just choose a product that provides the dose you want at a low cost -- generally 4 to 15 cents per 600 mg. (See ConsumerTips™). -
How much NAC should I take and when?
The dose of NAC used in clinical trials has ranged from about 600 mg to 3,000 mg per day, typically divided into two or three servings. See the What It Does section for the dosage for specific uses. -
Why are some retailers no longer selling NAC?
The FDA made it clear in 2020 that it considers NAC to be a drug and not a dietary supplement, so, for legal reasons, some companies have stopped selling it (See a href="#" data-toggle="modal" data-target="#review-modal">ConsumerTips™ for details). -
Safety and side effects of NAC:
NAC can cause headache and gastrointestinal side effects. It can also worsen asthma. For details, see Concerns and Cautions.
