N-Acetylcysteine: Benefits, Side Effects, Dosage, Interactions


N-acetylcysteine (NAC) is an additional form of the amino acid cysteine . Proponents argue that taking N-acetylcysteine supplements can protect against a host of health problems, including respiratory disease, liver disease, mental illness, diabetes, certain cancers, and chemical addiction.

NAC helps facilitate important biological functions by joining 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 control the immune system . Notably, glutathione helps neutralize free radicals that damage cells and tissues at the molecular level .

Cysteine occurs naturally in the body and comes from plant and animal foods. Because of this, cysteine is considered a semi-essential amino acid (unlike essential amino acids, which must be obtained from the outside).

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What is N-acetylcysteine used for?

In complementary and alternative medicine (CAM) , N-acetylcysteine is believed to help with a wide variety of diseases. Since N-acetylcysteine can increase glutathione production, some health professionals claim that it not only prevents conditions like cancer and heart disease by maintaining cell integrity, but also supports the treatment of certain diseases.

Proponents argue that N-acetylcysteine can prevent or treat a near-encyclopedic variety of health problems, including:

  • Allergic rhinitis (hay fever)
  • Alzheimer disease
  • Bipolar disorder
  • Bronchitis
  • Carbon dioxide poisoning
  • Chronic kidney disease
  • Chronic Obstructive Pulmonary Disease (COPD)
  • Cirrhosis
  • Cocaine addiction
  • Colon-rectal cancer
  • Conjunctivitis
  • Cystic fibrosis
  • Heart disease
  • Hepatitis
  • High cholesterol
  • HIV
  • Sterility
  • Lou Gehrig's disease
  • Lung cancer
  • Lupus
  • Polycystic Ovarian Syndrome (PCOS)
  • Post-traumatic distress syndrome (PTSD)
  • Premature delivery or miscarriage
  • Schizophrenia
  • Unstable angina
  • Upper respiratory tract infections

The broad nature of these claims borders on the implausible. Even the claims for which at least some related clinical studies exist are generally not true, either because the studies are small or because the evidence does not support the often wide-ranging conclusions.

At the same time, some positive results were obtained that deserve serious scientific consideration. These are some of the studies examining the benefits of N-acetylcysteine supplementation.


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

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


N-acetylcysteine may help prevent and treat diabetes, according to a 2016 study published in the American Journal of Translational Research. The study involved mice that were fed a high-fat diet (which mimics the effects of type 2 diabetes ) or drug-induced diabetes (which accurately mimics type 1 diabetes). Each group was subdivided into smaller groups according to the dose of N-acetylcysteine.

  • Doses of 600 to 1800 milligrams per kilogram per day (mg / kg / day) improved glucose tolerance in diabetic mice.
  • Mice fed the high-fat diet improved glucose levels at doses of 400 mg / kg / day and also achieved weight loss compared to mice given no N-acetylcysteine.
  • Doses of 1200 mg / kg / day increased insulin sensitivity.

While the results are preliminary, in fact they show promise for both the prevention and treatment of diabetes.

N-Acetylcysteine can provide better diabetes control by increasing a person's insulin sensitivity. By increasing glucose tolerance, N-acetylcysteine can 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 oxidative stress on the heart and cardiovascular system. This is supported in part by studies that found that taking daily N-acetylcysteine reduced hypertension (high blood pressure), one of the main contributors to atherosclerosis.

According to a 2015 study published in the American Journal of Clinical Nutrition, N-acetylcysteine reduces homocysteine levels in the blood. Homocysteine is an amino acid commonly obtained from 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 significant drops in systolic and diastolic blood pressure regardless of smoking, weight, or blood lipid levels.

Polycystic ovary syndrome

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

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

Male infertility

NAC can also improve fertility in men with infertility due to varicocele, which are the enlarged veins in the scrotum and testicles. Varicocele is one of the main causes of male infertility.

According to a 2016 study published in the International Journal of Fertility and Infertility, 35 men who underwent surgery to treat varicocele had higher fertility rates if they were given N-acetylcysteine before and after surgery.

In addition, the quality of the sperm has improved both physically and genetically. Researchers believe that the reduction in oxidative stress led to "healthier" sperm and improved fertility after varicocele surgery.

Bipolar disorder

There is some evidence that N-acetylcysteine may potentiate the effects of psychotropic drugs used to treat bipolar disorder. A 24-week study published in the International Journal of Bipolar Disorder found that 3,000 grams of NAC per day significantly improved depression rates in people taking bipolar medications.

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

Some scientists believe that the same benefits may extend to other mental disorders, including substance use 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 oral administration of N-acetylcysteine does not prevent or treat the symptoms of a Tylenol overdose in any way. Tylenol poisoning is considered a medical emergency – call 911 right away if you or someone you know may have overdosed on acetaminophen.

Possible side effects.

N-Acetylcysteine is considered safe and well tolerated when used correctly. That said, it can cause side effects for some.

Common side effects are usually mild and usually go away on their own after stopping treatment. They may include:

  • Nausea
  • Abdominal pain
  • Diarrhea

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

N-acetylcysteine allergy is rare, but can occur. The risk is higher during N-acetylcysteine infusions. In rare cases, the infusion can cause anaphylaxis , a life-threatening allergic reaction.

Allergies to oral N-acetylcysteine are usually mild, but can cause a runny nose, sneezing, and nasal congestion. Call your doctor if symptoms persist or worsen, or if you develop a rash or dizziness.

N-Acetylcysteine is generally considered safe to use during pregnancy and while breastfeeding. However, talk to your doctor or OB / GYN to fully understand the risks and benefits of N-acetylcysteine in your case and whether or not you really need a supplement.


N-Acetylcysteine has several known drug interactions. This can enhance the action of nitroglycerin and isosorbide dinitrate used to treat angina , causing headaches, dizziness, dizziness, or fainting.

There is also a theoretical risk of hypoglycemia (low blood sugar) if N-acetylcysteine is taken with diabetes medications. Regular monitoring of blood glucose levels can help detect any abnormal drop in blood sugar.

Warnings and contraindications.

A safe and effective oral dose of N-acetylcysteine for children has not been established. N-acetylcysteine supplements should not be used in children unless directed by a doctor.

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

Caution should be exercised in people with kidney disease. The metabolized NAC is excreted through the kidneys and is known to rarely cause kidney stones , even in people without kidney disease .

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Dosage and preparation

Oral N-acetylcysteine supplements are available over the counter in tablets, capsules, softgels, effervescent, and powders. Most are sold in 600 milligram (mg) forms, although some go as high as 1,000 mg.

There are no universal recommendations for the correct use of N-acetylcysteine. Doses of up to 1200 mg per day (usually in divided doses) have been used safely in adults. As a general rule, never take more than the recommended dose indicated on the product label.

Single amino acid supplements, such as N-acetylcysteine, are best taken on an empty stomach. Amino acid absorption can be affected by the foods you eat them with and other amino acids.

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

What to look for

Nutritional supplements are not strictly regulated in the United States and can vary significantly from brand to brand. To ensure maximum safety and quality, buy only supplements that have been tested by an independent certification body such as the United States 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 indicator that the ingredients are safe.

You should avoid any supplement that claims to cure anything. Supplement manufacturers are prohibited by law from making such claims because they lack large-scale clinical studies to back them up.

N-Acetylcysteine supplements are made in the laboratory from synthetic compounds and are suitable for vegans and vegetarians. If you are vegan and prefer softgel capsules, choose foods that say 'vegan' on the label to avoid animal gelatin.

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Food contains only a small amount of N-acetylcysteine. However, cysteine deficiency is not very common, although vegetarians and vegans with a low intake of plant foods rich in cysteine may be at risk.

Those working to ensure adequate NAC levels may consider supplementation, but also consider consuming these foods, which are excellent sources of amino acids: poultry, eggs, dairy, red bell peppers, garlic, onions, broccoli, and tea. D Brussels sprouts, oats, and wheat germ.

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