Natural Medicines Comprehensive Database 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. The effectiveness ratings for NIACIN are as follows:

Likely effective for…

  • Abnormal levels of cholesterol or blood fats (dyslipidemia). Some niacin products are approved by the U.S. Food and Drug Administration (FDA) as prescription products for treating abnormal levels of blood fats. These prescription products typically come in high strengths of 500 mg or higher. Dietary supplement forms usually come in strengths of 250 mg or less. Since very high doses are required for improving cholesterol levels, dietary supplement niacin usually isn’t appropriate. Niacin may be combined with other cholesterol-lowering drugs when diet and single-drug therapy is not enough. It improves cholesterol levels, but does not improve cardiovascular outcomes such as heart attacks and strokes.
  • A disease caused by niacin deficiency (pellagra). Niacin is approved by the U.S. Food and Drug Administration (FDA) for this use. However, it can cause “flushing” (redness, itching, and tingling). So another product, called niacinamide, is sometimes preferred because it doesn’t cause this side effect.

Possibly effective for…

  • Abnormal levels of blood fats in people with HIV/AIDS. Taking it seems to improve levels of cholesterol and blood fats called triglycerides in patients with this condition.
  • A grouping of symptoms that increase the risk of diabetes, heart disease, and stroke (metabolic syndrome). Taking niacin 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. Taking it along with a prescription omega-3 fatty acid seems to work even better.

Ineffective for…

  • Heart disease. High-quality research shows that it does not prevent heart attack or stroke in people who take niacin to prevent or treat heart disease. Niacin has also not been shown to reduce the risk of death. It should not be taken to treat or prevent heart disease.

Insufficient evidence to rate effectiveness for…

  • Hardening of the arteries (atherosclerosis). Taking it by mouth along with medicines called bile acid sequestrants might reduce hardening of the arteries in men with this condition. It seems to work best in men with high levels of blood fats called triglycerides. But taking niacin does not seem to reduce the hardening of the arteries in patients with a condition called peripheral arterial disease (PAD). Also, it does not prevent cardiovascular events such as a heart attack or stroke.
  • Alzheimer disease. People who consume higher amounts from food and multivitamins seem to have a lower risk of getting Alzheimer’s disease than people who consume less niacin. But there is no evidence that taking a niacin supplement helps to prevent Alzheimer’s disease.
  • Cataracts. People who eat a diet high in niacin might have a reduced chance of developing nuclear cataracts. Nuclear cataract is the most common type of cataract. The effect of taking niacin supplementation is unknown.
  • An infection of the intestines that causes diarrhea (cholera). Taking niacin by mouth seems to reduce diarrhea in people with cholera.
  • Erectile dysfunction (ED). Taking extended-release niacin at bedtime for 12 weeks seems to help men who have ED and high lipid levels maintain an erection during sexual intercourse.
  • High levels of phosphate in the blood (hyperphosphatemia). People with kidney failure might have high blood levels of phosphate. Some early research shows that taking niacin can reduce blood levels of phosphate in people with end-stage kidney disease and high levels of blood phosphate. But other research shows that taking niacin does not lower blood phosphate levels in people who are also taking medications used to lower blood phosphate levels.
  • Blockage of the vein in the eye (retinal vein occlusion): Early research shows that taking niacin might improve eyesight in people with this condition.
  • Sickle cell disease: Early research shows that taking niacin does not improve the levels of blood fats in people with sickle cell disease.
  • Acne.
  • Alcohol use disorder.
  • Athletic performance.
  • Attention deficit-hyperactivity disorder (ADHD).
  • Depression.
  • Dizziness.
  • Drug-induced hallucinations.
  • Migraine.
  • Motion sickness.
  • Schizophrenia.
  • Other conditions.

More evidence is needed to rate niacin for these uses.

Side Effects Of Niacin

  • When taken by mouth: Niacin is LIKELY SAFE for most people when taken 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 mcg daily.
  • A common side effect is a flushing reaction. This might cause burning, tingling, itching, and redness of the face, arms, and chest, as well as headaches. Starting with small doses of niacin and taking 325 mg of aspirin before each dose of niacin will help reduce the flushing reaction. Usually, this reaction goes away as the body gets used to the medication. Alcohol can make the flushing reaction worse. Avoid large amounts of alcohol while taking niacin.
  • Other minor side effects are stomach upset, intestinal gas, dizziness, pain in the mouth, and other problems.
  • When doses of over 3 grams per day are taken, more serious side effects can happen. These include liver problems, gout, ulcers of the digestive tract, loss of vision, high blood sugar, irregular heartbeat, and other serious problems.

Warnings & Precautions

  • Pregnancy and breast-feeding: Niacin is LIKELY SAFE for pregnant and breastfeeding women when taken by mouth in the recommended amounts. The maximum recommended amount for pregnant or breast-feeding women is 30 mg per day for women under 18 years of age, and 35 mg for women over 18.
  • Children: Niacin is LIKELY SAFE when taken by mouth in the recommended amounts for each age group. But children should avoid taking doses above the daily upper limits, which are 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, the chemical responsible for allergic symptoms, to be released.
  • Heart disease/unstable angina: Large amounts can increase the risk of irregular heartbeat. Use with caution.
  • Crohn disease: People with Crohn disease might have low levels and require supplementation during flare-ups.
  • 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 might bring on gout.
  • Kidney disease: Niacin might accumulate in people with kidney disease. This might cause harm.
  • Liver disease: Niacin might increase liver damage. Don’t use large amounts if you have liver disease.
  • Stomach or intestinal ulcers: Niacin might make ulcers worse. Don’t use large amounts if you have ulcers.
  • Very low blood pressure: Niacin might lower blood pressure and worsen this condition.
  • Surgery: Niacin might interfere with blood sugar control during and after surgery. Stop taking it at least 2 weeks 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 the symptoms of certain thyroid disorders.

Dosage Of Niacin

The following doses have been studied in scientific research:



  • General: Some dietary supplement products list niacin on the label in niacin equivalents (NE). 1 mg of niacin is the same as 1 mg NE. When niacin is listed on a label as NE, it might include other forms of niacin as well, including niacinamide, inositol nicotinate, and tryptophan. The daily recommended dietary allowances (RDAs) for niacin in adults are 16 mg NE for men, 14 mg NE for women, 18 mg NE for pregnant women, and 17 mg NE for lactating women.
  • For high cholesterol: The effects of niacin are dose-dependent. Doses of niacin as low as 50 mg and as high as 12 grams each day have been used. However, the biggest increases in HDL and decreases in triglycerides occur at 1200 to 1500 mg/day. Niacin’s greatest effects on LDL occur at 2000 to 3000 mg/day. Niacin is often used with other medications for improving cholesterol levels.
  • For preventing and treating vitamin B3 deficiency and related conditions such as pellagra: 300-1000 mg daily in divided doses.
  • For treating hardening of the arteries: Doses have been as high as 12 grams daily. However, a dose of about 1 to 4 grams daily, alone or along with statins or bile acid sequestrants (a cholesterol-lowering medicine), has been used for up to 6.2 years.
  • For reducing fluid loss caused by cholera toxin: 2 grams daily has been used.
  • For abnormal blood fat levels due to treatment for HIV/AIDS: Up to 2 grams daily has been used.
  • For metabolic syndrome: 2 grams has been taken daily for 16 weeks. In some cases, niacin 2 grams daily, alone or at this dosage, is taken along with 4 grams of prescription omega-3 ethyl esters (Lovaza, GlaxoSmithKline Pharmaceuticals).


  • For preventing and treating vitamin B3 deficiency and related conditions such as pellagra: 60 mg of niacin has been used.


  • For preventing and treating vitamin B3 deficiency and related conditions such as pellagra: 60 mg has been used.



  • General: The daily recommended dietary allowances (RDAs) in children are 2 mg NE for infants 0-6 months of age, 4 mg NE for infants 7-12 months of age, 6 mg NE for children 1-3 years of age, 8 mg NE for children 4-8 years of age, 12 mg NE for children 9-13 years of age, 16 mg NE for boys 14-18 years of age, and 14 mg NE for girls 14-18 years of age.

For preventing and treating vitamin B3 deficiency and related conditions such as pellagra: 100-300 mg per day, given in divided doses.


Consult your doctor or pharmacist.


All information has been provided courtesy of MedLinePlus from the National Library of Medicine and from the FDA.