Acetylcysteine (NAC): what it is and what to know
Acetylcysteine, also called NAC (N-acetylcysteine), is a form of the amino acid cysteine. Many people know it as a medicine for coughs with thick mucus, but it is also sold as a food supplement.
In this article you will learn how NAC differs from ordinary supplements, what research shows and when it should be used with caution.
In brief. N-acetylcysteine (NAC) is a form of the amino acid cysteine that is attracting growing interest. The body can make glutathione from NAC – one of the most important antioxidants in cells.2 Researchers are studying NAC in a variety of directions, and the effect may differ from person to person.¹ NAC is also used as a medicine. Therefore, if you are taking other medicines, talk to your doctor or pharmacist before you start taking NAC.2
What is NAC?
We get cysteine from protein-rich foods: meat, eggs, dairy products and legumes. NAC is a form of cysteine used in medicines and supplements.2
In the body, glutathione is made from cysteine. This is a substance that takes part in protecting cells and in liver metabolism.2 Because of this connection, NAC is often associated with glutathione.
When is NAC used as a medicine?
- In paracetamol poisoning. In hospital, NAC is given as an antidote.2
- Thick mucus in the airways. NAC thins mucus, so in many countries it is sold as a medicine for coughs with phlegm.2
In a review of studies, mucus-thinning medicines, including NAC, slightly reduced the number of flare-ups in people with chronic bronchitis or chronic obstructive pulmonary disease.3 This is a treatment prescribed by a doctor. Food supplements are not intended to treat diseases.
What this means for you. If a cough has lasted longer than 3 weeks or keeps coming back, see a doctor rather than choosing a supplement on your own.4
What doses are found in supplements?
Supplements most often contain 150–600 mg of NAC per capsule. For medicines, the dose is specified by your doctor or the package leaflet. For a supplement, follow the dose stated by the manufacturer.
Example. If you take a 600 mg NAC capsule and a "liver" or "detox" complex that also contains NAC, add up the amount from both products. In complexes, the amount of NAC is sometimes not even stated.
How to choose a NAC product?
- Pure or complex. In a pure product you can clearly see the amount of NAC. In complexes it is combined with selenium, milk thistle or other substances, so it is important to check the full composition.
- Dose. If you are taking it for the first time, it is more convenient to start with a lower dose and observe how you feel.
- Capsule. Plant-based capsules are suitable for vegans. Gelatine capsules are made from animal-derived raw materials.
Side effects and caution
The most common side effects are nausea, vomiting and diarrhoea.2 NAC capsules may have a distinctive sulphur smell, because cysteine contains sulphur.
Talk to your doctor first if:2
- you take nitroglycerin or other nitrates – headache may become stronger and blood pressure may drop;
- you have asthma;
- you are pregnant or breastfeeding;
- you take activated charcoal – it may reduce the effect of NAC;
- you have surgery coming up or have bleeding disorders.
Selected NAC products
Commercial information. These are products available in our shop. This is not a ranking of effectiveness. Before buying, check the composition and directions for use on the product page.
150 mg of N-acetyl-L-cysteine per capsule, take 1 capsule per day with a meal. The lowest dose of those listed here. The capsule contains gelatine.5
N-Acetyl-L-Cysteine, 600mg - 60 caps - Life Extension
600 mg of N-acetyl-L-cysteine per capsule, plant-based capsule. The manufacturer recommends 1 capsule 1–3 times per day. Discuss higher doses with your doctor.6
NAC with Selenium, 600mg - 100 caps - NOW Foods
Each capsule contains 600 mg of NAC and 25 µg of selenium. Take 1 capsule per day. If you also take other supplements containing selenium, add up the amount.7
NAC Detox, Selenium & Molybdenum - 60 vegan caps - Osavi
A complex: 190 mg of NAC, 125 mg of milk thistle extract, choline, 160 µg of selenium and 150 µg of molybdenum per capsule. The selenium content is high, so do not take other selenium supplements together with it.8
Frequently asked questions
How does NAC differ from a glutathione supplement?
NAC is a substance from which the body makes glutathione itself.2 In glutathione supplements, it is already ready-made. If you are considering which to choose, talk to a pharmacist.
Does NAC help with a cold?
NAC thins mucus, so as a medicine it is sometimes used for a cough with phlegm.2 If a cold has dragged on or you have a fever, see a doctor.
When is the best time to take NAC?
Follow the manufacturer's instructions. When taken with food, nausea occurs less often.
Scientific sources
- Europos Komisija. EU Register of nutrition and health claims made on foods. ec.europa.eu
- MedlinePlus, U.S. National Library of Medicine. N-acetyl cysteine. medlineplus.gov
- Poole P, Sathananthan K, Fortescue R. Mucolytic agents versus placebo for chronic bronchitis or chronic obstructive pulmonary disease. Cochrane Database Syst Rev. 2019;5:CD001287. doi:10.1002/14651858.CD001287.pub6
- NHS. Cough. nhs.uk
- Swanson. NAC, 150 mg, 60 capsules. Product label.
- Life Extension. N-Acetyl-L-Cysteine, 600 mg, 60 capsules. Product label.
- NOW Foods. NAC with Selenium, 600 mg, 100 capsules. Product label.
- Osavi. NAC Detox, Selenium & Molybdenum, 60 capsules. Product label.
Disclaimer. This article is for informational purposes only and does not replace a consultation with a doctor or pharmacist. Food supplements are not intended to treat or prevent diseases and are not a substitute for a varied diet and a healthy lifestyle. Before taking supplements, especially during pregnancy or breastfeeding, if you have a chronic illness or if you are taking medicines, consult a healthcare professional.
