Niacin
Niacin

Background

Niacin is a form of vitamin B3 made in the body from tryptophan. It's found in many foods including meat, fish, milk, eggs, green vegetables, and cereals.

Niacin is required for the proper function of fats and sugars in the body and to maintain healthy cells. At high doses, niacin might help people with heart disease because of its effects on blood clotting. It might also improve levels of fats called triglycerides in the blood.

Prescription forms of niacin are approved by the US FDA for abnormal cholesterol levels and for preventing vitamin B3 deficiency and related conditions such as pellagra. People use niacin supplements for metabolic syndrome, heart disease, cataracts, high blood pressure, and many other conditions, but there is no good scientific evidence to support most of these other uses.

Do not confuse niacin with NADH, niacinamide, inositol nicotinate, IP-6, or tryptophan. These are not the same.
When taken by mouth: Niacin is likely safe for most people when used appropriately. Prescription products containing niacin are safe when taken as directed. Niacin-containing foods or niacin supplements are safe when taken in doses lower than 35 mg daily.

A common side effect of niacin is a flushing reaction. This might cause burning, itching, and redness of the face, arms, and chest, as well as headaches. Starting with small doses and taking 325 mg of aspirin before each dose of niacin may help. This reaction usually goes away as the body gets used to niacin.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Niacin is likely safe when taken by mouth while pregnant and breast-feeding. The maximum recommended amount of niacin while pregnant or breast-feeding is 30 mg daily in those under 18 years of age, and 35 mg daily for those 19 years and older.

Children: Niacin is likely safe when taken by mouth in doses below the tolerable upper intake level (UL) by age. The UL is 10 mg for children 1-3 years of age, 15 mg for children 4-8 years of age, 20 mg for children 9-13 years of age, and 30 mg for children 14-18 years of age.

Allergies: Niacin might worsen allergies by causing histamine to be released. Histamine is the chemical responsible for allergic symptoms.

Chest pain (angina): Niacin should be used cautiously in people with angina.

Diabetes: Niacin might increase blood sugar. People with diabetes who take niacin should check their blood sugar carefully.

Gallbladder disease: Niacin might make gallbladder disease worse.

Gout: Large amounts of niacin might increase the risk for gout.

Kidney disease: Niacin might accumulate in people with kidney disease. This might cause harm.

Liver disease: Taking high doses of niacin might increase liver damage. Don't use large amounts if you have liver disease.

Low blood pressure: Taking niacin in high doses might lower blood pressure and worsen this condition.

Stomach or intestinal ulcers: Niacin might make ulcers worse. Don't use large amounts if you have ulcers.

Surgery: Niacin might interfere with blood sugar control during and after surgery. Speak with your healthcare provider about whether you should stop taking niacin before a scheduled surgery.

Fatty deposits around tendons (tendon xanthomas): Niacin might increase the risk of infections in xanthomas.

Thyroid disorders: Thyroxine is a hormone produced by the thyroid gland. Niacin might lower blood levels of thyroxine. This might worsen symptoms of certain thyroid disorders.

Effectiveness

Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
Likely effective Effectiveness definitions
  • Abnormal levels of cholesterol or blood fats (dyslipidemia). Taking niacin prescription products by mouth in doses of 500 mg or more improves cholesterol levels in people with abnormal cholesterol. Dietary supplement forms of niacin usually come in lower doses and don't seem to improve blood fat levels.
  • A disease caused by niacin deficiency (pellagra). Niacin prescription products are US FDA approved for preventing and treating pellagra.
Possibly effective Effectiveness definitions
  • Abnormal levels of blood fats in people with HIV/AIDS. Taking prescription niacin products by mouth seems to improve levels of cholesterol and blood fats called triglycerides in people with this condition. It is unclear if niacin supplements are helpful.
  • A grouping of symptoms that increase the risk of diabetes, heart disease, and stroke (metabolic syndrome). Taking prescription niacin products by mouth seems to increase levels of high-density lipoprotein (HDL or "good") cholesterol and reduce levels of blood fats called triglycerides in people with metabolic syndrome. It is unclear if niacin supplements are helpful.
Likely ineffective Effectiveness definitions
Possibly ineffective Effectiveness definitions
  • Heart disease. Taking niacin by mouth does not prevent heart attack or stroke in people with or without heart disease.
There is interest in using niacin for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.
Insufficient evidence Effectiveness definitions

Dosing & administration

In supplements, niacin is listed on the label in niacin equivalents (NE). 1 mg of niacin is the same as 1 mg NE. When niacin is listed as NE, it might include other forms of niacin, including niacinamide, inositol nicotinate, and tryptophan.

Niacin is also found in many foods, including meat, fish, milk, eggs, vegetables, and cereals. The amount that should be consumed on a daily basis is called the recommended dietary allowance (RDA). In males 14 years and older, the RDA is 16 mg NE. In females 14 years and older, the RDA is 14 mg NE. While pregnant, the RDA is 18 mg NE. While breast-feeding, the RDA is 17 mg NE. In children, the RDA depends on age. Speak with a healthcare provider to find out what dose might be best for a specific condition.

Interactions with pharmaceuticals

Alcohol (Ethanol)

Interaction Rating=Moderate Be cautious with this combination.

Niacin can cause flushing and itchiness. Consuming alcohol along with niacin might make the flushing and itching worse. There is also some concern that consuming alcohol with niacin might increase the chance of having liver damage.

Allopurinol (Zyloprim)

Interaction Rating=Moderate Be cautious with this combination.

Allopurinol is used to treat gout. Taking large doses of niacin might worsen gout and decrease the effects of allopurinol.

Aspirin

Interaction Rating=Minor Be watchful with this combination.

Aspirin is often used to reduce the flushing caused by niacin. These low doses of aspirin don't seem to cause any issues when taken with niacin. But taking higher doses of aspirin, such as 1 gram daily, might decrease how fast the body gets rid of niacin. This could cause there to be too much niacin in the body and possibly lead to side effects. Stick with lower doses of aspirin, such as 325 mg or less.

Gemfibrozil (Lopid)

Interaction Rating=Moderate Be cautious with this combination.

Taking niacin along with gemfibrozil might increase the risk for muscle damage in some people. Use with caution.

Medications for diabetes (Antidiabetes drugs)

Interaction Rating=Moderate Be cautious with this combination.

High doses of niacin might increase blood sugar levels. Taking niacin along with diabetes medications might reduce the effects of these medications. Monitor your blood sugar closely.

Medications for high blood pressure (Antihypertensive drugs)

Interaction Rating=Moderate Be cautious with this combination.

Niacin might lower blood pressure. Taking niacin along with medications that lower blood pressure might cause blood pressure to go too low. Monitor your blood pressure closely.

Medications that can harm the liver (Hepatotoxic drugs)

Interaction Rating=Moderate Be cautious with this combination.

Niacin might harm the liver. Some medications can also harm the liver. Taking niacin along with a medication that can harm the liver might increase the risk of liver damage.

Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs)

Interaction Rating=Moderate Be cautious with this combination.

Niacin might slow blood clotting. Taking niacin along with medications that also slow blood clotting might increase the risk of bruising and bleeding.

Medications used for lowering cholesterol (Bile acid sequestrants)

Interaction Rating=Moderate Be cautious with this combination.

Some medications called bile acid sequestrants can decrease how much niacin the body absorbs. This might reduce the effects of niacin. Take niacin and these medications at least 4-6 hours apart.

Medications used for lowering cholesterol (Statins)

Interaction Rating=Moderate Be cautious with this combination.

Taking niacin along with statins might increase the risk for muscle damage in some people. Use with caution.

Nicotine patch (Nicoderm)

Interaction Rating=Moderate Be cautious with this combination.

Niacin can sometimes cause flushing and dizziness. Nicotine patches can also cause flushing and dizziness. Taking niacin and using a nicotine patch may increase the risk of flushing and dizziness.

Probenecid (Benemid)

Interaction Rating=Moderate Be cautious with this combination.

Probenecid is used to treat gout. Taking large doses of niacin might worsen gout and decrease the effects of probenecid.

Sulfinpyrazone (Anturane)

Interaction Rating=Moderate Be cautious with this combination.

Sulfinpyrazone is used to treat gout. Taking large doses of niacin might worsen gout and decrease the effects of sulfinpyrazone.

Thyroid hormone

Interaction Rating=Moderate Be cautious with this combination.

The body naturally produces thyroid hormones. Niacin might decrease thyroid hormone levels. Taking niacin with thyroid hormone pills might decrease the effects of thyroid hormone.

Interactions with herbs & supplements

Beta-carotene: Taking niacin along with antioxidants, including beta-carotene, might reduce the beneficial effects that niacin has on cholesterol levels.
Chromium: Taking niacin and chromium together might lower blood sugar. If you have diabetes and take chromium and niacin supplements together, monitor your blood sugar to make sure it doesn't get too low.
Herbs and supplements that might harm the liver: Niacin might harm the liver. Taking it with other supplements that can also harm the liver might increase the risk of liver damage. Examples of supplements with this effect include garcinia, greater celandine, green tea extract, kava, and kratom.
Herbs and supplements that might lower blood pressure: Niacin might lower blood pressure. Taking it with other supplements that have the same effect might cause blood pressure to drop too much. Examples of supplements with this effect include andrographis, casein peptides, L-arginine, niacin, and stinging nettle.
Herbs and supplements that might slow blood clotting: Niacin might slow blood clotting and increase the risk of bleeding. Taking it with other supplements with similar effects might increase the risk of bleeding in some people. Examples of supplements with this effect include garlic, ginger, ginkgo, nattokinase, and Panax ginseng.
Selenium: Taking niacin along with antioxidants, including selenium, might reduce the beneficial effects that niacin has on cholesterol levels.
Vitamin C: Taking niacin along with antioxidants, including vitamin C, might reduce the beneficial effects that niacin has on cholesterol levels.
Vitamin E: Taking niacin along with antioxidants, including vitamin E, might reduce the beneficial effects that niacin has on cholesterol levels.
Zinc: People who are malnourished and have niacin deficiency, such as those with alcohol use disorder, make extra niacin if they take zinc. There might be an increased risk of niacin-related side effects such as flushing and itching if niacin and zinc are taken together.

Interactions with foods

Drinking alcohol or hot drinks can make the flushing reaction associated with niacin worse. Avoid drinking large amounts of alcohol or hot drinks while taking niacin.
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This monograph was last reviewed on 20/04/2022 22:12:45 and last updated on 17/10/2020 02:13:07. Monographs are reviewed and/or updated multiple times per month and at least once per year.
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