|December 7, 2023

NAC Benefits: What To Know About N-Acetyl Cysteine

By Spencer Brooks
Reviewed by Emily Gonzalez, ND for Scientific Accuracy

NAC Benefits: What To Know About N-Acetyl Cysteine

  • N-acetyl cysteine, also known as NAC, is a dietary supplement associated with immune support, detoxification and more. It can also help increase your body’s levels of glutathione.
  • Glutathione is a powerful antioxidant that can help reduce oxidative stress and free radical damage—to both support a healthy inflammation response and slow down the effects of aging.
  • Here’s everything you need to know about NAC benefits and supplementation.

N-acetyl cysteine, or NAC, is a dietary supplement that may help your body produce an important antioxidant called glutathione, which in turn can help protect against free radicals.[1] Read on to learn all about NAC benefits, how NAC supplements can help support glutathione and how best to take NAC.

What is NAC?

Also called N-acetyl-L-cysteine, NAC is the supplement version of an essential amino acid called cysteine.[2] Amino acids are the building blocks of proteins. Cysteine is one of three amino acids (along with glycine and glutamine) that make up glutathione, an important antioxidant found in nearly all of your body’s cells.

In this way, NAC helps your body produce glutathione. Glutathione is known as the “master antioxidant” because of its prevalence throughout the body and ability to support other antioxidants.[3] The problem is that glutathione tends to decline with age. It can also be reduced by factors like poor nutrition, stress and environmental contaminants.

Taking NAC supplements may help replenish your glutathione levels.

NAC benefits

NAC is used as a medicine that can treat conditions ranging from liver damage to asthma to acetaminophen overdose. It has been well-studied by medical researchers and has an array of potential health benefits. Generally considered to be a safe and well-tolerated supplement, NAC is also relatively inexpensive.[4]

If you’re thinking of supplementing with NAC, know that it can help with:


One of the benefits of NAC is that it has been found to correct naturally occurring glutathione deficiency, which happens as humans age.[5] Glutathione can help make you more resistant to oxidative stress, slowing down aging at a cellular level.[6]


NAC helps protect cells from toxicity caused by environmental pollutants, including pesticides[7], heavy metals like lead[8] and gasoline and diesel fumes.[9] [10]

It’s also a standard treatment at hospitals for acetaminophen overdoses and poisons that cause damage through extreme oxidative stress.


NAC has been found to improve egg quality and increase pregnancy rates in women with polycystic ovary syndrome (PCOS).[11]

NAC may even help reverse weight gain and prediabetes, two common symptoms of PCOS.[12] In men, NAC improves sperm quality and, in some cases, even reverses infertility.[13] Researchers think this happens because NAC is so adept at protecting cells from oxidative damage. Increasing antioxidant status may help keep sperm healthier.


Clinical trials have found that NAC can help support a healthy inflammatory response in the body, which is helpful for relieving symptoms of respiratory conditions like chronic obstructive pulmonary disease (COPD) and improving insulin resistance.[14] [15]

Immune function

NAC has been used as a mucolytic drug in some European countries, though there’s little new research on its effects.[16]

How and when to take NAC, morning or night

Most studies use a dose of between 1200-2400 mg, taken in 600 mg doses throughout the day.[17][18][19][20] If you’re wondering when to take NAC, morning or night, know that it doesn’t matter exactly when you take it. However, you’ll absorb oral N-acetylcysteine supplements best if you take them on an empty stomach, at least an hour away from eating.

Some oral N-acetylcysteine supplements have a strong odor that might not be pleasant to take before sleep. As with any dietary supplement, be sure to check in with your doctor or healthcare provider before you begin taking NAC.

Keep in mind that NAC can result in side effects in some people, especially when taken at high levels. Common side effects of high doses of NAC can include diarrhea, nausea, vomiting and constipation.

How long does it take for NAC to work?

Pills on blue background

One of the biggest questions you’ll have before starting to supplement with NAC is: How long does it take for NAC to work?

A 2015 double-blind, placebo controlled study of middle-aged men found reduced signs of oxidative stress after four weeks of taking NAC, including improvements in blood pressure and cardiovascular health.[21]

Want to learn more about how glutathione can help support your overall health and wellness? Read our comprehensive guide to glutathione.

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This article has been updated with new content.