What to Know About NAC Supplements

NAC is both a medication and a supplement. As a medication it has proven benefits for preventing liver damage from acetaminophen poisoning. As a supplement it has many possible benefits, but no proven benefits.

NAC supplements that may have benefits

Don’t ignore the powerful NAC benefits to be had from this form of the amino acid L-cysteine.

NAC, the acronym for N-acetylcysteine, is used as both a prescription medication and an over-the-counter supplement. As a medication, NAC has proven benefits for preventing liver damage caused by an overdose of acetaminophen (Tylenol). It is also used as a medication to break up mucous in the lungs, although the evidence for this benefit is not as strong. [1,2]

By far, the most common use of NAC is as a supplement. NAC is a naturally occurring amino acid. In the body, NAC is turned into glutathione, a powerful antioxidant. NAC and other antioxidants are popular supplements because of their potential to prevent cell damage. [2,3]

When you exercise, convert food into energy, or you are exposed to sunlight or toxins, free radicals are produced. Free radicals are unstable molecules that can cause cell damage. This damage is called oxidative stress. Antioxidants prevent oxidative stress. [4]

Possible Benefits of Antioxidant Supplements

According to the National Center for Complementary and Integrative Health, there is good evidence for benefits from antioxidants in fruits and vegetables. The evidence of antioxidant benefits from supplements is not as good. In well controlled studies of over 100,000 people, no consistent evidence was found that antioxidant supplements prevent chronic disease, cancer, or heart disease. [4]

Who Should Take NAC

NAC supplements are popular and are taken for many reasons. The benefits have been studied in cell and animal studies, and less frequently in human studies. Here are the most common uses:

  • Depression, though studies on NAC for depression have mixed results. There is no evidence that NAC can be used as a treatment for depression. [2]
  • Cancer; however, there is no evidence that NAC prevents cancer, but some evidence that it may reduce side effects from cancer treatments. [2]
  • Substance abuse. Some human studies have found that NAC may reduce drug abuse, but other studies have not found any benefits. [2]
  • Athletic performance. Some human studies have found benefits for NAC to improve exercise and athletic performance. [3]
  • Anti-aging. Claims for these benefits are based mainly on animal studies showing improvement in age related loss of brain functions, called neurodegeneration. In human studies, NAC has shown some improvement in brain function (cognition) and in chronic fatigue syndrome. [3]

How to take NAC

NAC is available in supplements. There is no established dose. In studies, dose ranges varied widely from just over one gram to 20 grams. Since the Food and Drug Administration does not regulate supplements, and the dose changes with how the supplements are made, there is no way to know the best dose. The best option is to follow the directions on the supplement label. [3]

Risks of Taking NAC Supplements

NAC may interfere with certain medications, including nitroglycerin (a heart medicine) and carbamazepine (an anti-seizure medication). Side effects may include:

  • Nausea
  • Vomiting
  • Diarrhea
  • Fatigue
  • Eye irritation
  • Skin rash [1,2]

Less common side effects are headache, low blood pressure, allergy, or asthma attack. [2] Although NAC is usually safe in most supplement doses, higher doses for use as an athletic enhancer, or long-term dosing have not been studied. Because antioxidants may protect cancer cells as well as normal cells, high-dose antioxidants have been linked to lung cancer in smokers and prostate cancer. [3]

Memorial Sloan Kettering Cancer Center says that some cancer drugs may create free radicals to kill cancer cells. Taking NAC may interfere with these drugs. If you are taking a chemotherapy drug for cancer, check with your doctor before taking NAC. [2]

The Bottom Line on NAC

According to a 2019 review of NAC supplement benefits published in the journal Antioxidants, the most promising benefits so far in humans are for neurodegeneration. Future studies in humans will probably tell us more about benefits, safety, and the most effective doses for various uses. [3] For now, there is not enough evidence to recommend NAC as a treatment or prevention for any condition. Talk to your doctor if you would like to try this or any other antioxidant supplement. [2,3,4]


  1. Mayo Clinic, Acetylcysteine (Inhalation Route) Description and Brand Names – Mayo Clinic
  2. Memorial Sloan Kettering Cancer Center, N-Acetylcysteine | Memorial Sloan Kettering Cancer Center (mskcc.org)
  3. Antioxidants, Medical and Dietary Uses of N-Acetylcysteine (nih.gov)
  4. National Center for Complementary and Integrative Health, Antioxidants: In Depth, Antioxidants: In Depth | NCCIH (nih.gov)

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Chris Iliades, MD

Chris Iliades has an MD degree and 15 years of experience as a freelance writer. Based in Boothbay Harbor, Maine, his byline has appeared regularly on many health and medicine … Read More

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  • This is an amazing article on what sounds to be an amazing supplement. Thank you!
    One question, how does it compare to an oxaloacetate supplement,or are they the same? Thanks again.

  • Appreciate this update as there were studies on mice that seemed less than positive. Should I get a cold of flu, I will try NAC which I’ve purchased and will report back here on its effectiveness.

  • I have suffered acute bronchitis for many years, and coupled with colds and flu, have been rendered physically wrecked. In the last 12 months, i have taken n.a.c faithfully, and to date have not had any recurring bronchitis, or colds or flu for that matter. Day one of taking this supplement, i awoke the next day and my sinuses cleared completely. I have noticed an increase in physical stamina, well being, and mood. I have been a heavy smoker for decades, and was diagnosed with borderline copd. friends and relatives have remarked on how well i look, and i really do believe in the power of this amazing antioxidant, and am doing my best to extol its virtues to anyone i meet who appears to be suffering some malaise or other. I also consume 12mg of Boron daily, and i no longer suffer with stiff joints and mild arthiritis. There have been a couple of friends that reported no difference to their health at all. I have read that this may be because they already have sufficient levels of glutathione in their system!

  • NAC is the supplement that helped both my husband and me with watery/dry eye symptoms. My eyes watered, his were dry…we started taking NAC and our respective problems cleared up. (Both are due to the same thing: inflammation of eye duct). We take NAC for other things as well but we were elated that it cleared up these small but super annoying problems.

  • I have been on before, but because of tummy aches stopped, but am so concerned with lack of deep breathing efforts am retrying it……I pray it helps me, I have COPD, Histo and Fibro….am a mess but hopeful…………any comments appreciated….

  • Been taking NAC (along with vitamin C) for several years now. It has really helped with the mucin (NOT the same as mucus) so many hypothyroid patients have, myself included.

  • After my 3rd pulmonary embolism in 2003, I was diagnosed with pulmonary fibrosis and I read that people usually die within 5 years. My specialist has me on blood thinners, prednisone and other steroids that I inhale daily. October 2006 I decided to go with natural treatment and was introduced to Green House Herbal Clinic natural organic idiopathic pulmonary fibrosis Herbal formula, i had a total decline of symptoms with this pulmonary fibrosis Herbal formula treatment. The infections, shortness of breath, fatigue, dry cough and other symptoms has subsided. Somehow, the herbs managed to keep me alive for 13 years.Visit Green House Herbal Clinic official website w ww.greenhouseherbalclinic .com or email herbs@ greenhouseherbalclinic. com. I have had great improvement with my over all respiration with this product and i breath very much easier, i can never be thankful enough to nature

  • After my 3rd pulmonary embolism in 2003, I was diagnosed with pulmonary fibrosis and I read that people usually die within 5 years. My specialist has me on blood thinners, prednisone and other steroids that I inhale daily. October 2006 I decided to go with natural treatment and was introduced to Green House Herbal Clinic natural organic idiopathic pulmonary fibrosis Herbal formula, i had a total decline of symptoms with this pulmonary fibrosis Herbal formula treatment. The infections, shortness of breath, fatigue, dry cough and other symptoms has subsided. Somehow, the herbs managed to keep me alive for 13 years.Visit Green House Herbal Clinic official website I have had great improvement with my over all respiration with this product and i breath very much easier, i can never be thankful enough to nature

  • I have had extreme joint (back and knees) for 30 years I have OCD I have struggled with gambling depression anxiety I have been taking 600 mg of NAC for two weeks all conditions have gone away It’s a miracle my blood pressure is back to 117/69 from a high norm of 148/90 I’m happy I feel 20 years younger I can do full knee squats I now have a true disbelief in conventional doctors and medicine also no side effects at all love it take it change my life it will change your life!!

  • My Husband was diagnosed with Idiopathic pulmonary fibrosis 5 years ago and was on minimum daily dosage prednisone (7.5 mg), azathioprine and N-Acetyl. They put him on 6 liters of oxygen and steroids to slow down progression. His symptoms have always been shortness of breath, and coughing badly. the prednisone wasn’t really working and he could not tolerate them for long due to severe side effects, There has been little if any progress in finding a cure or reliable treatment. So this year his primary physician suggested we started him on Natural Herbal Gardens Idiopathic Pulmonary Fibrosis Herbal formula which eased his anxiety a bit,, We ordered their IPF herbal treatment after reading alot of positive reviews, i am happy to report with the help of Natural Herbal Garden natural herbs we have been able to reverse my husband symptoms using herbs, his symptoms totally declined over a 9 weeks use of the Natural Herbal Gardens IPF natural herbal formula. His Idiopathic pulmonary fibrosis is totally reversed! Their official web page is naturalherbalgardens . c o m After the herbal treatment he also finally was able to give up smoking after 20 years. We are thankful to nature, herbs are truly gift from God

  • About 4 years ago, no risk factors, out of the blue, I was diagnosed with TB. I had a bad cough, was losing weight. It wasnt until I could not breathe, that I went to the Dr. So six months of quarantine and a year of antibiotics later, I was told I had 20 percent of my lung function remaining and would need inhalers, steriods, respirators to aid me during my downhill slide. I never. Took any of those, was doing ok, but began suffering periodic bouts of pnuemonia. I did some research and put myself on a regiment of medicinal mushrooms (cordyceps, reishi, chaga) a tea I make with ginger, tumuric and raw honey and 600 mg of NAC twice a day. Now I should be on oxygen, I’m not running any marathons, but as a rustic artist/carpenter, I work hard, hike evey day the weather permits, generally exibit a higher level of health then others my age (51) And I hate to admit, but I still smoke. I’m not sure which of my supplements has the greatest effect, but I did run out of NAC for a week once and noticed greater congestion. I am completely med free and living normally.

  • I’ve been taking NAC for about a week now and noticed that I’m actually coughing more right after taking. I take 500 mg in the morning and immediately it feels like I have a dry cough. Is this normal?

  • I wanted to quit tobacco for the last 10yrs and I could not with any of those suggested methods, and now just by taking this once daily….The Craving is gone! I mean. So low that you can handle it, and I quit! along with that, it feels far better altogether. I wake up and feel fresh, and have far more energy. It feels like I have a new body again… I was missing this NAC in my body all my life… I mean since like the age of 25! Honestly, there is nothing negative about this. I also lost weight as well! (the cravings of all kinds have gone away such as eating too much, drinking too much, smoking too much!). Healthy levels in the blood, blood pressure, and really mentally better. It’s really insane that I didn’t know about this all my life.

  • I actually discovered NAC on my own research, by constantly digging for information through my Amazon account I was reading other people’s comments about different things one thing led to another thing I kept reading all these ups and downs good and bad comments about different supplements and I decided from my own conclusion that I would try NAC and L-CITRULLINE, I purchased the ingredients from bulk supplements this product was pure Crystal powder form uncut unblemished. I have COPD and other health issues kidney problems and I could not get any relief from any doctor that I went to the prescription medications not working for me and I took these prescriptions for about 24 years. It was about 4 years ago that I noticed, that every time I would eat watermelon I could breathe better so I started asking different doctors that I went to, why, I ask the doctors why is it everytime I eat watermelon I can breathe better and my sinuses are open my lungs feel like I’m getting enough air and every doctor that I asked would say I have no idea, never heard of it. Anyway l-citrulline is a product that comes from watermelon so along with l-citrulline and The NAC supplements I have been taking them approximately six months now and how about the first month I started taking them is when I quit taking my prescription inhalers I don’t even use them anymore I am so glad that I found something that is actually curing not just masking but actually curing my COPD along with the chronic bronchitis the phlegm the mucus I’m a happy person now and I’m 65 years old an ex-smoker. After doing some further research I’m fixing to add two more supplements 2 my supplements that I am now taking and those are L-Carnitine and magnesium glycine there are many different types of magnesium. If there is anyone out there that would like to discuss this further with me you can email me my email address is,,,rayzone.rt@gmail.com

  • I have been taking N-A-C for a couple of weeks. Yes, my depressive symptoms are down, I do not obsessed as much as I did before. I have more energy – but I have a hard time sleeping,feeling so energetic. My nose is stuffed and I have a hard time blowing it – the mucus is so thick.

  • Have Hashimotos with neuropathy in hands. Have tried NAC 3 times as it really helps with tingling but my stomach can’t tolerate it. Makes my stomach tight and I have no appetite. Will have to move on to something else

  • Thanks for this helpful info about NAC.
    I started taking it back in 2014 as part of s healing protocol that involved different supplements at different times and then intestinal cleansing on and off.
    One of the health coaches I met early on said if he could only take one supplement it would be NAC. He said it was because of the powerful way it helped heal the liver, which is the body’s filter and is usually stressed when people are ill. Make that – the liver is often stressed long before people show symptoms of illness.
    Over the years I have taken NAC (on and off) in low amounts and recently tried a new brand (a brand I love for their b-right complex) and wear taking 600 mg once time a day – this article helped tremendously because within a few days of taking it I noticed I was clearing my lungs a lot (expectorant qualities here) and felt a few other things you noted here. So I cut my dose in half to help adjust my use of it.
    People should keep in mind that sometimes we have a healing crisis (herx reaction) when we start healing the body – this means we need to go slow or back off from a supplement – but it does not mean to abandon it. Especially if our body needs it – we might feel
    Blah for a little while.
    Also – going slow with healing is ideal.
    After finally realizing the powerful impact of NAC my goal is to work up to two 600 my doses a day – and also take my other supplements as many things work synergistically –
    I noticed that my liver formulas have had NAC in them too and this wonderful supplement is an elixir for the liver. And even if we have not taken tylenol or alcohol – many people have a stressed liver (like high fructose corn syrup can scar the liver) and so it is just a good idea to support this vital organ!
    Another one
    Of my health mentors will not work with anyone with healing packages until they have supported their liver for two months – and NAC is part of that.
    Thanks again for this informative article

  • I have been taking for several weeks and my coughing is gone. My eyes are really white and my nose is clear.
    I think it is important that folks know they need to drink lots of water taking NAC and need to add a supplement of minerals a few hours after taking or a few hours before because NAC may keep you from obsorbing them. There is a great article about NAC in “Science Daily” Good Luck

  • This is w/reference to use of NAC….I came across it while ordering the cytokine suppress which helps with my psoriasis along w/CBD oil for that and remission of hand arthritis/trigger fingers…but wanted a supplement w/aid to the bronchial cough w/some mucus. Had stopped smoking over a year and half….and w/our hot air heat on, starting using a small humidifier in bedroom but wasn’t clearing. Rec’d the NAC (taking for several days) and I read your articles on this site…have noticed a big decrease in the coughing/mucus/and slight wheeze……I’m 73 (been a smoker for several decades)…am going to increase from 1…600 mg. to twice a day w/lots more water…..glad to have read so many successful reports from others….will stop back in a month or so…..thank you!

  • NAC is great unless you have mercury in your system. It can chelate it out to fast and can be redeposited in other body parts – ie brain. Does help with respiratory system. I love it but its not for everyone.

  • I am the grandparent of a child with Cri du Chat Syndrome. Parents on the support boards are reporting high doses (up to 2600mg)are helping with behavioral issues – especially skin picking and OCD-like behaviors are greatly reduced.

  • I started taking NAC somewhat by accident as it was in an Omega supplement I ordered. I’ve always had allergies…I can breathe more clearly than at any point in my life. It’s really wonderful. Not sure about all the brain stuff – but when you can breath you notice it right away!

  • i have been taking 600mg a day for couple years.my breathing a lot better.sometimes i up the dose to 2x day if sick.

  • tried to get my brother to take since he diagnosed with copd,but he would rather listen to his doctor who said it wouldnt help.oh well

  • I saw a show on the Dr. Oz show about 3 or 4 years ago about the pulmonary benefits of taking NAC. I had bad allergies towards dust, molds, animal fur and pollutants mainly. I was clearing my throat constantly and prone to some sinus infections at times. I had a hard time talking without sounding like I had a frog in my throat all the time. My mom even commented how I had a bad habit by clearing my throat all the time. I knew then it was bad and it wasn’t a habit. I started to taking 600mg. 3 times a day because I was so severe with post nasal drip almost choking on it often. It was the best supplement I have ever taken. It changed my life. I was also seeing a Holistic dr that would recommend herbal medicine for me. It didn’t seem to help me or not much if any. I called her to ask her if it’s ok for me to take NAC? Would I develop an allergy towards it someday? She said it was fine for me and I should be fine with it. I sure hope so because it changed my life entirely for years now. I am even able to own 4 cats now for almost 4 years. So I must of be on it for 5 years then. I rarely ever get the flu or sinus infection anymore. I have never had a cold since I started taking it. I felt improvement within a week and I kept on improving over the years. I am so thankful I saw his show when I did. I probably wouldn’t have been able to hold down the job I have working with the public. I have to talk a lot and sell products. I believe it gave me great quality of life. I buy the good quality ones called Pure Encapsulations. It doesn’t have cheap fillers so it absorbs well into the system. Over the years I have had to eat something now or it gives me heart burn. As long as I do I am fine.

  • I had Lyme disease and take NAC regularly. I didn’t believe that it worked so two years ago I asked my doctor to run a flu titer after a season when my kids all had it. Turns out I had the flu and never knew it. I just recently stopped taking it as I thought I was in the clear for the winter season and what do you know I have some kind of upper respiratory infection I caught from my kiddo.

  • I picked itchy sores on my scalp for 10 years. They were horrible and I was ashamed. I went to many doctors who told me to stop scratching or they would never heal. I tried about 75 different suggestions but nothing worked. I read a research paper about NAC, 1,000 mg in am, 2,000 mg before bed. OMG, it worked. I no longer have sores on my scalp to puck at. I will never stop being grateful for this research.

  • I have been taking NAC for the last week and already notice a difference! I have inherited asthma from my grandfather and mother and was diagnosed with COPD, although I think the COPD diagnosis is bunk.
    I have been able to get mucus out of my system and my chest doesn’t feel as tight from the asthma as it did before. I’m hoping that with prolonged use, it will go away entirely!
    I take 500 mg in the morning and 500 mg in the evening. I’m not sure if I should increase my dosage or not but I might try. Maybe using NAC will get me off the medications altogether. Here’s hoping!
    Has anyone ever had a reaction to NAC? I am experiencing a couple of things. Dry mouth and the odd dizzy spell. These could be from anything but I’ve noticed them since starting NAC.

  • I have had a problem with pathological skin picking for many, many years, if not my whole life. In the last year during which I suffered severe depression and anxiety, my skin picking became dire. I was also unable to hide it anymore given it was really bad on my face (in addition to my left thigh, my right arm and sometimes, my chest and/or buttocks). I tried many methods to try to stop, but was unable to. My doctors were unable to help. I started researching online and found various sources recommending NAC. As I was desperate, rather than capsules/tablets I bought the powdered form despite reports of its significant unpalatability (they were right, it’s awful). I managed to take a single dose of between 2g to 3g daily by dissolving it in pure blueberry or cherry juice. Within a couple of weeks, I’d finally stopped picking and my sores are well on the way to healing. Hopefully the scars will also fade. Given I started on a very high dose, it’s not surprising I also experienced typical side-effects: diarrhoea and nightly waves of skin itches (very different to the skin picking issue, and did not result in injuries from scratching). I believe the itching was a sign of the detoxifying effects of NAC. I also began taking MCT oil at the same time, so the diarrhoea could be related to that or both supplements? I was amazed at the cessation of skin picking and have taken every opportunity to let my doctors and friends know of this. It seems to me that there are many years of research supporting the use of NAC in various settings eg. pulmonary problems, OCD behaviours like mine & treating addictions – given it is cheap and relatively benign (unlike other current treatments) it makes me frustrated and angry that NAC is not prescribed more often. Is it because there is no profit in it for pharmaceutical companies??? As a side result, I’ve had excessive mucus in the lungs since a very bad infection in my teens. Since taking NAC, the mucus has significantly lessened. I also suffer from chronic fatigue and although that’s still a feature of my days, it’s not as bad as it was. I feel the NAC has helped reset my doses of Modafinil, which had lost efficacy over the years. I stopped taking Modafinil/Nuvigil and when I occasionally feel I really need its help, it works better than it has in a long time (did NAC detox me of Modafinil build-up so new doses of the drug could work again?). I’m now trying a tablet form of NAC and hope this will continue to work (the juice was too much sugar on a daily basis and affecting my weight). I am a big fan of NAC and hope to see more mainstream doctors, particularly those in general practice, aware of it and willing to prescribe it. Thanks for your work on this website.

  • I truly developed pneumonia last month of May and nothing, I mean nothing would help me get rid of the excess mucus. My Dr didn’t know what else to do as he had prescribed antibiotics, predisdone, more steroids and more steroids even a nebulizer. Nothing was working and I was still coughing non stop . I took this int my own hands and began taking NAC and guess what it’s all gone, no wheezing either.

  • Im trying to figure out why NAC worked so well for me and the stopped working after a week?! Desperate to find out why! Histamine reaction? Vitamin deficiency? Upped dose to quick? (3 caps)I corrected these things still not working taking for myxedema mucin/fluid through the body from low thyroid function anyone have any info? Ty

  • 1st Phychologist appt today, I have the above to take twice a day in powder form mixed with water. 60g. I want to believe her but am scared. I have addiction, anxiety, depression and OCD. Maybe it won’t hurt to try?

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