N-Acetyl Cysteine (NAC)


N-acetyl cysteine is an amino acid that serves as a precursor for the synthesis of glutathione, a detoxifying agent in the body. NAC also functions as an antioxidant that has been used to combat viruses. It may also help the liver detoxify a wide range of pollutants such as cigarette smoke, auto exhaust, certain herbicides, and some toxic metals.

NAC may also reduce the viscous mucous associated with respiratory diseases like chronic bronchitis. It is also used as an antidote for acetaminophen poisoning. (1)

N-acetyl cysteine does not occur in foods. Its precursor, L-cysteine, occurs in most high-protein foods.

Dosage Info

Dosage Range

250 to 2,000mg daily. However, doses of 20 grams per day may be used to treat acetaminophen poisoning.

Most Common Dosage

500mg, 2 times daily.

Dosage Forms

Capsules, tablets, powder, and solution.

Interactions and Depletions


Reported Uses

Acetaminophen overdose results in more calls to poison control centers in the U.S. than an overdose from any other pharmaceutical substance. N-acetyl cysteine remains the therapy of choice in the treatment of acetaminophen poisoning. In such cases, it prevents depletion of an important protective antioxidant, glutathione, which protects the liver from damage. (2)

NAC’s protective properties may also extend to the treatment of heavy metal poisoning. It can potentially neutralize such harmful metals as mercury, arsenic, chromium, and boron while protecting the liver and kidneys from their damaging effects. (3) , (4) As part of its role in protecting the liver, NAC may help the body fight hepatitis and enhance the performance of pharmaceutical hepatitis treatments. (5)

NAC may support the health of the respiratory system and help reduce the production of excess mucous associated with respiratory illnesses. When added to asthma medications, for example, NAC may reduce mucous secretions without side effects. (6)

NAC may also offer treatment for chronic bronchitis by lowering the recurrence of the infections and, again, by reducing mucous secretion. (7) This benefit, combined with its role as an antioxidant may also make NAC beneficial in the treatment of chronic obstructive pulmonary disease (COPD).

NAC may reduce factors that can place one at higher risk of cardiovascular diseases like atherosclerosis and thrombosis (clogging of the arteries). (8) Additionally, because NAC is a precursor for the antioxidant glutathione, it may be useful for AIDS and HIV patients, who are commonly deficient in glutathione. (9) NAC may also stimulate immune response in HIV-infected patients. (10)

NAC may help lower the toxicity of some chemotherapy treatments, thereby reducing cardiovascular damage, nausea, and other symptoms. (11) , (12) Finally, NAC may help inhibit the development of retinopathy in individuals with diabetes, as demonstrated in some animal experiments. (13)

Toxicities & Precautions


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This dietary supplement is considered safe when used in accordance with proper dosing guidelines.

Do not attempt to use NAC to treat acetaminophen poisoning. Call a poison control center immediately.

Side Effects

Occasional side effects reported with the use of this dietary supplement include varying degrees of nausea, vomiting, headache, dry mouth, dizziness, or abdominal pain. (14) Tell your doctor if these side effects become severe or do not go away.

Pregnancy / Breast Feeding

To date, the medical literature has not reported any adverse effects related to fetal development during pregnancy or to infants who are breast-fed. Yet little is known about the use of this dietary supplement while pregnant or breast-feeding. Therefore, it is recommended that you inform your healthcare practitioner of any dietary supplements you are using while pregnant or breast-feeding.

Age Limitations

To date, the medical literature has not reported any adverse effects specifically related to the use of this dietary supplement in children. Since young children may have undiagnosed allergies or medical conditions, this dietary supplement should not be used in children under 10 years of age unless recommended by a physician.


  1. View Abstract: Koivusalo AM, Yildirim Y, Vakkuri A, Lindgren L, Hockerstedt K, Isoniemi H. Experience with albumin dialysis in five patients with severe overdoses of paracetamol. Acta Anaesthesiol Scand. Oct2003;47(9):1145-50.
  2. View Abstract: Zed PJ, Krenzelok EP. Treatment of acetaminophen overdose. Am J Health Syst Pharm. Jun1999;56(11):1081-91.
  3. View Abstract: Ballatori N, et al. N-acetylcysteine as an antidote in methylmercury poisoning. Environ Health Perspect. May1998;106(5):267-71.
  4. View Abstract: Flora SJ, et al. Arsenic-induced oxidative stress and its reversibility following combined administration of N-acetylcysteine and meso 2,3-dimercaptosuccinic acid in rats. Clin Exp Pharmacol Physiol. Nov1999;26(11):865-9.
  5. View Abstract: Beloqui O, et al. N-acetyl cysteine enhances the response to interferon-alpha in chronic hepatitis C: a pilot study. J Interferon Res. Aug1993;13(4):279-82.
  6. View Abstract: Millman M, et al. Use of acetylcysteine in bronchial asthma--another look. Ann Allergy. Apr1985;54(4):294-6.
  7. View Abstract: Riise GC, et al. The intrabronchial microbial flora in chronic bronchitis patients: a target for N-acetylcysteine therapy? Eur Respir J. Jan1994;7(1):94-101.
  8. View Abstract: Gavish D, et al. Lipoprotein (a) Reduction by N-Acetylcysteine. Lancet. Jan1991;337:203-204.
  9. View Abstract: Roberts RL, et al. N-acetylcysteine enhances antibody-dependent cellular cytotoxicity in neutrophils and mononuclear cells from healthy adults and human immunodeficiency virus-infected patients. J Infect Dis. Dec1995;172(6):1492-502.
  10. View Abstract: Breikrutz R, et al. Improvement of immune functions in HIV infection by sulfur supplementation: two randomized trials. J Mol Med. 2000;78(1):55-62.
  11. View Abstract: DeFlora S, et al. Synergism between N-acetylcysteine and doxorubicin in the prevention of tumorigenicity and metastasis in murine models. Int J Cancer. Sep1996;67(6):842-8.
  12. de Blasio R, et al. N-acetylcysteine (NAC) in preventing nausea and vomiting induced by chemotherapy in patients suffering from inoperable non-small cell lung cancer (NSCLC). Chest. 1996;110(4,Suppl):103S.
  13. Kowluru RA, Tang J, Kern TS. Abnormalities of retinal metabolism in diabetes and experimental galactosemia. VII. Effect of long-term administration of antioxidants on the development of retinopathy. Diabetes. Aug2001;50(8):1938-42.
  14. View Abstract: Tattersall AB, et al. Acetylcysteine (Fabrol) in chronic bronchitis--a study in general practice. J Int Med Res. 1983;11(5):279-84.