The Health Benefits of N-Acetylcysteine

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

In This Article

N-acetylcysteine (NAC) is the supplement form of the amino acid cysteine. The supplement helps facilitate essential biological functions by bonding with two other amino acids—glutamine and glycine—to create a powerful antioxidant known as glutathione.

Glutathione plays a key role in regulating numerous cellular activities and helps keep the immune system in check. As an antioxidant, glutathione helps neutralize free radicals that damage cells and tissues at the molecular level.

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.

Health Benefits

In complementary and alternative medicine, N-acetylcysteine is believed to help a wide range of medical conditions. Because N-acetylcysteine can increase the production of glutathione, some practitioners have posited that it not only prevents conditions like cancer and heart disease by maintaining the integrity of cells but also support 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
  • Hypercholesterolemia (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 occasionally borders on the far-fetched. Even those claims that have benefited from clinical research typically fall short, either because the studies are small or the evidence doesn't support the often far-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 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 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. Among the findings:

  • 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 both in the prevention and management of diabetes.

N-acetylcysteine may provide better control of diabetes by increasing a person's sensitivity to insulin. On the flip side, 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 can 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 an amino acid you commonly get from eating red meat. High levels 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 showed that N-acetylcysteine improved ovulation and pregnancy rates compared to a placebo.

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

Male Infertility

While N-acetylcysteine may improve fertility in with PCOS, it is unclear whether it can do the same with men with infertility due to varicoceles. Varicoceles are one of the leading causes of male infertility, resulting from the formation of varicose veins in the scrotum.

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 the physical and genetic level. 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 N-acetylcysteine 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.

Tylenol Poisoning

One of the medical indications of N-acetylcysteine is Tylenol (acetaminophen) poisoning. The procedure involves three consecutive intravenous (IV) infusions given over 24 hours to prevent liver damage and other symptoms of acetaminophen toxicity.

Tylenol poisoning is considered a medical emergency. Taking oral N-acetylcysteine in no way prevents or treats symptoms of a Tylenol overdose.

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, stomach ache, and 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 potentially life-threatening allergy characterized by severe rash, hives, clamminess, shortness of breath, rapid heart rate, and the swelling of the face, throat, and tongue.

Allergies to oral N-acetylcysteine tend to be mild and may cause a runny nose, sneezing, and nasal congestion. Call your doctor 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 doctor or OB/GYN to fully understand the risks and benefits of N-acetylcysteine 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, and 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

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

Caution should also be exercised in people with kidney disease. The metabolized drug is excreted via the kidneys and has been known in rare cases to cause kidney stones even in people without kidney disease.

Dosage and Preparation

Oral N-acetylcysteine supplements are available over the counter in tablet, capsule, soft gel, effervescent, and powdered form. 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.

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

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 of any supplements that have expired, are discolored or 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.

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 cures. Under the law, dietary supplement manufacturers are barred from doing so as they lack the large-scale clinical research to support such claims.

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


Only minute amounts of N-acetylcysteine are found in food. By contrast, 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).

Excellent food sources of cysteine include:

  • Poultry
  • Red meat (especially pork)
  • Eggs
  • Dairy
  • Red peppers
  • Garlic
  • Onions
  • Broccoli
  • Brussels sprouts
  • Oats
  • Wheat germ

Cysteine deficiency is not very common, although vegetarians and vegans with a low intake of cysteine-rich plant foods may be at risk.

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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.