What Is N-Acetylcysteine?

This amino acid may help with diabetes, COPD, and infertility

N-Acetylcysteine powder, tablets, and capsules

Verywell / Anastasia Tretiak

N-acetylcysteine (NAC) is the supplement form of the amino acid cysteine. Proponents claim that taking N-acetylcysteine supplements can protect against a plethora of health concerns, including respiratory diseases, liver disease, psychiatric disorders, diabetes, certain cancers, and chemical dependency.

NAC helps facilitate essential biological functions by bonding with two other amino acids—glutamine and glycine—to create glutathione, a powerful antioxidant that plays a key role in regulating numerous cellular activities and helps keep the immune system in check. Of particular note, glutathione helps neutralize free radicals that damage cells and tissues at the molecular level.

Cysteine is both naturally produced in the body and obtained from animal- and plant-based foods. Because of this, cysteine is considered a semi-essential amino acid (unlike essential amino acids that must be obtained externally).

Health Issues N-Acetylcysteine Might Help Treat
Laura Porter / Verywell

What Is N-Acetylcysteine Used For?

In complementary and alternative medicine (CAM), N-acetylcysteine is believed to help a wide range of medical conditions. Because N-acetylcysteine can increase the production of glutathione, some healthcare providers have posited that it not only prevents conditions like cancer and heart disease by maintaining the integrity of cells, but also supports the treatment of certain diseases.

Proponents contend that N-acetylcysteine has the potential to prevent or treat an almost encyclopedic range of health problems, including:

  • Allergic rhinitis (hay fever)
  • Alzheimer's disease
  • Bipolar disorder
  • Bronchitis
  • Carbon dioxide poisoning
  • Chronic kidney disease
  • Chronic obstructive pulmonary disorder (COPD)
  • Cirrhosis
  • Cocaine dependence
  • Colorectal cancer
  • Conjunctivitis
  • Cystic fibrosis
  • Heart disease
  • Hepatitis
  • High cholesterol
  • HIV
  • Infertility
  • Lou Gehrig's disease
  • Lung cancer
  • Lupus
  • Polycystic ovary syndrome (PCOS)
  • Post-traumatic distress syndrome (PTSD)
  • Preterm labor or miscarriage
  • Schizophrenia
  • Unstable angina
  • Upper respiratory infections

The expansive nature of these claims borders on far-fetched. Even those claims for which there is at least some related clinical research typically fall short, either because the studies are small or the evidence doesn't support the often over-reaching conclusions.

With that being said, there have been some positive findings that warrant serious scientific consideration. Here is a look at some of the research investigating the benefits of N-acetylcysteine supplements.


Numerous studies have looked into the benefits of N-acetylcysteine supplements in people with chronic bronchitis and chronic obstructive pulmonary disease (COPD).

A 2015 analysis published in European Respiratory Review, evaluating 13 studies and a total of 4,155 people with COPD, concluded that 1,200 milligrams (mg) of N-acetylcysteine per day reduced the incidence and severity of flares (known as exacerbations) compared to a placebo.


N-acetylcysteine may aid in the prevention and management of diabetes, suggests a 2016 study in the American Journal of Translational Research. The research involved mice that were either fed a high-fat diet (replicating the effects of type 2 diabetes) or had medical-induced diabetes (closely mirroring type 1 diabetes). Each group was further divided into smaller groups based on N-acetylcysteine dose.

  • Doses of 600 to 1,800 milligrams per kilogram per day (mg/kg/day) improved glucose tolerance in mice with medically-induced diabetes.
  • Mice fed high-fat diets had improved glucose at doses of 400 mg/kg/day and also achieved weight loss compared to mice not given N-acetylcysteine.
  • Doses of 1,200 mg/kg/day increased insulin sensitivity.

While the results are preliminary, they do show promise in both the prevention and management of diabetes.

N-acetylcysteine may provide better control of diabetes by increasing a person's sensitivity to insulin. By increasing glucose tolerance, N-acetylcysteine may prevent people with prediabetes from progressing to diabetes.

High Blood Pressure

N-acetylcysteine is often said to reduce the risk of heart disease by reducing the oxidative stress on the heart and cardiovascular system. This is evidenced in part by research in which the daily use of N-acetylcysteine was found to reduce hypertension (high blood pressure), a major factor for atherosclerosis.

According to a 2015 study in the American Journal of Clinical Nutrition, N-acetylcysteine reduces levels of homocysteine in the blood. Homocysteine is an amino acid commonly obtained by eating red meat, and high levels of it are an independent risk factor for heart disease, kidney disease, and even recurrent miscarriage.

The researchers reported that a four-week course of N-acetylcysteine was associated with a significant drop in systolic and diastolic blood pressure irrespective of smoking, weight, or blood lipid values.

Polycystic Ovary Syndrome

N-acetylcysteine may help treat polycystic ovary syndrome (PCOS), according to a 2015 systematic review in Obstetrics and Gynecology International. In evaluating eight studies with a total of 910 women with PCOS, the investigators found that N-acetylcysteine improved ovulation and pregnancy rates compared to a placebo.

The cause for this is not entirely clear. Despite the findings, the researcher reported that N-acetylcysteine did not improve other common symptoms of PCOS, including menstrual irregularities, weight gain, and the development of secondary male traits.

Male Infertility

NAC may also improve fertility in men with infertility due to varicoceles, which are enlarged veins in the scrotum and testicles. Varicoceles are one of the leading causes of male infertility.

According to a 2016 study in the International Journal of Fertility and Sterility, 35 men who underwent surgery to treat varicoceles had higher rates of conception if given N-acetylcysteine prior to and after surgery.

Moreover, the quality of sperm was also seen to improve, both on physical and genetic levels. The researchers believe that the alleviation of oxidative stress resulted in "healthier" sperm and improved fertility following varicoceles surgery.

Bipolar Disorder

There is some evidence that N-acetylcysteine can enhance the effects of psychotropic drugs used to treat bipolar disorder. A 24-week study published in the International Journal of Bipolar Disorder reported that 3,000 grams of NAC a day significantly improved depression scores in people on bipolar medications.

It is believed the antioxidant effects triggered by N-acetylcysteine may be responsible for the response. Most experts agree that an imbalance of oxidants and antioxidants is a central feature of clinical depression.

Some scientists believe that the same benefits may extend to other psychiatric disorders, including substance abuse disorders and early schizophrenia.

Acetaminophen Poisoning

N-acetylcysteine is used to treat Tylenol (acetaminophen) poisoning. Three consecutive intravenous (IV) infusions of NAC are given over 24 hours to prevent liver damage and other symptoms of acetaminophen toxicity.

Note that taking oral N-acetylcysteine in no way prevents or treats symptoms of a Tylenol overdose. Tylenol poisoning is considered a medical emergency: call 911 immediately if you or someone you know may have overdosed on acetaminophen.

Possible Side Effects

N-acetylcysteine is considered safe and well-tolerated if used appropriately. With that said, it may cause side effects in some.

Common side effects are generally mild and typically resolve on their own once treatment is stopped. These may include:

  • Nausea
  • Stomachache
  • Diarrhea

Less commonly, people may experience a runny nose, drowsiness, and fever.

Allergies to N-acetylcysteine are uncommon but can occur. The risk is highest during N-acetylcysteine infusions. In rare cases, an infusion may cause anaphylaxis, a life-threatening allergic reaction.

Allergies to oral N-acetylcysteine tend to be mild, but may cause a runny nose, sneezing, and nasal congestion. Call your healthcare provider if the symptoms persist or worsen, or if you develop a rash or dizziness.

N-acetylcysteine is generally considered safe to use during pregnancy and breastfeeding. Even so, speak with your healthcare provider or OB/GYN to fully understand the risks and benefits of N-acetylcysteine in your case and whether you actually need the supplement or not.


N-acetylcysteine has few known drug interactions. It may intensify the effects of nitroglycerin and isosorbide dinitrate used to treat angina, causing headaches, dizziness, lightheadedness, or fainting.

There is also a theoretical risk of hypoglycemia (low blood sugar) if N-acetylcysteine is taken with diabetes medications. The routine monitoring of blood glucose can help identify any abnormal drops in blood sugar.

Warnings and Contraindications

A safe and effective oral dose of N-acetylcysteine in children has not been established. Unless directed by a healthcare provider, N-acetylcysteine supplements should not be used in children.

N-acetylcysteine can slow blood clotting and should be avoided in people with bleeding disorders, such as hemophilia or Von Willebrand disease.

Caution should be exercised in people with kidney disease. Metabolized NAC is excreted via the kidneys and has been known to cause kidney stones in rare cases—even in people without kidney disease.

N-acetylcysteine tablets
Verywell / Anastasia Tretiak

Dosage and Preparation

Oral N-acetylcysteine supplements are available over the counter in tablet, capsule, softgel, effervescent, and powdered forms. Most are sold in 600-milligram (mg) formulations, although some are as high as 1,000 mg.

There are no universal guidelines on the appropriate use of N-acetylcysteine. Doses of up to 1,200 mg per day (generally taken in divided doses) have been used safely in adults. As a rule of thumb, never take more than the recommended dosage listed on the product label.

Single amino acid supplements, like N-acetylcysteine, are best taken on an empty stomach. The absorption of amino acids can be affected by the foods you take them with and by other amino acids.

N-acetylcysteine supplements can be stored at room temperature in a cool, dry room. Discard any supplements that have expired, are discolored, or are show signs of deterioration.

What to Look For

Dietary supplements are not strictly regulated in the United States and can vary significantly from one brand to the next. To ensure the utmost safety and quality, only buy supplements that have been tested by an independent certifying body like the U.S. Pharmacopeia (USP), ConsumerLab, or NSF International.

Such certification does not mean that the supplement is effective in treating any medical condition; it simply confirms that it contains the ingredients listed on the product label and is a good indication that the ingredients are safe.

You should avoid any supplement that makes claims about curing anything. Under the law, dietary supplement manufacturers are barred from making such statements since they lack the large-scale clinical research to support them.

N-acetylcysteine supplements are manufactured in the lab with synthetic compounds and are vegan- and vegetarian-friendly. If you are strictly vegetarian and prefer softgel caps, only opt for products with "vegan" on the label to avoid animal-based gelatins.

A Word From Verywell

Only minute amounts of N-acetylcysteine are found in food. Still, cysteine deficiency is not very common, although vegetarians and vegans with a low intake of cysteine-rich plant foods may be at risk.

Those working to make sure they have adequate levels of NAC can consider supplementation, but should also be mindful about consuming these foods, which are excellent food sources of the amino acid: poultry, eggs, dairy, red peppers, garlic, onions, broccoli, Brussels sprouts, oats, and wheat germ.

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5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Gaucher C, Boudier A, Bonetti J. Glutathione: Antioxidant Properties Dedicated to Nanotechnologies. Antioxidants (Basel). 2018 May;7(5):62. doi:10.3390/antiox7050062.

  2. Talarowska M, Szemraj J, Berk M, et al. Oxidant/antioxidant imbalance is an inherent feature of depression. BMC Psychiatry. 2015:15:17.doi:10.1186/s12888-015-0454-5.

  3. Tomko RL, Jones JL, Gilmore AK, et al. N-acetylcysteine: A potential treatment for substance use disorders. Curr Psychiatr. 2018 Jun;17(6):30-55.

  4. Conus P, Seidman LJ, Fournier M, et al. N-acetylcysteine in a Double-Blind Randomized Placebo-Controlled Trial: Toward Biomarker-Guided Treatment in Early Psychosis. Schizophr Bull. 2018 Feb;44(2):317-27. doi:10.1093/schbul/sbx093.

  5. Sansone A, Sansone L. Getting a Knack for NAC: N-Acetyl-Cysteine. Innov Clin Neurosci. 2011 Jan;8(1):10-14.

Additional Reading
  • Barekat F, Tavalee M, Deemeh MR, et al. A Preliminary Study: N-acetyl-L-cysteine Improves Semen Quality following Varicocelectomy. Int J Fertil Steril. 2016 Apr-Jun;10(1):120-6. doi:10.22074/ijfs.2016.4777.

  • Cazzola M, Calzetta L, Page C, et al. Influence of N-acetylcysteine on chronic bronchitis or COPD exacerbations: a meta-analysis. Eur Respir Rev. 2015;24:451-61. doi:10.1183/16000617.00002215.

  • Falach-Malik A, Rozenfeld H, Chetborn M, et al. N-Acetyl-L-Cysteine inhibits the development of glucose intolerance and hepatic steatosis in diabetes-prone mice. Am J Transl Res. 2016;8(9):3744-56.

  • Hildebrandt W, Sauer R, Bonaterra G, et al. Oral N-acetylcysteine reduces plasma homocysteine concentrations regardless of lipid or smoking status. Am J Clin Nutr. 2015 Nov;102(5):1014-24. doi:10.3945/ajcn.114.101964.

  • Thakker D, Raval A, Patel I, et al. N-Acetylcysteine for Polycystic Ovary Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Clinical Trials. Obstet Gynecol Int. 2015;2015:817849. doi:10.1155/2015/817849.