Niacin Flush, High-Dose Niacin for Cholesterol and Liver Safety
Why high-amount niacin causes flushing, what large trials found when it was added to statins for cholesterol, liver risks, official upper limits and who should ask a clinician.
Content last updated . This page has not been medically reviewed.
Urgent first
If a child has swallowed a large amount of any vitamin, call Poison Help at 1-800-222-1222 (US) or 911 if they are unwell; other countries are listed at poison help by country. If you take high-amount niacin and develop symptoms that worry you, contact a clinician; see liver safety.The short answer
Niacin (vitamin B3) at the small amounts found in food and ordinary vitamins is a normal nutrient. At the much higher amounts once used as a cholesterol medicine, it causes flushing and can harm the liver, and large trials did not show it prevents heart attacks or strokes when added to statins. This page is information only. Please do not start, stop or change niacin or a statin because of it.Evidence labels used: established nutritional role, no good evidence of benefit, evidence of harm. Amounts from trials are study amounts, not advice.
Terms
Niacin is two compounds, nicotinic acid and nicotinamide (also called niacinamide), and both are found in food. [1] They behave differently at high amounts, which is why upper limits are set separately. [2] More on the differences: niacin, niacinamide and nicotinic acid compared and the niacin profile.Why the flush happens
The NHS says high doses of nicotinic acid supplements can cause skin flushes. [1] MedlinePlus describes flushing as warmth, redness, itching or tingling of the face, neck, arms or upper chest, seen when niacin is given as a treatment for high cholesterol. [3] A review explains that niacin activates receptors in skin cells, which raises prostaglandins and widens small blood vessels. [4] The same review reports that flushing is reduced with slower-release formulations, and that tolerance to flushing develops rapidly. [4]Nicotinamide does not produce the flush, according to EFSA (EU, 2002). [2] EFSA used the flush as the basis for the European upper limit because of concerns about brief drops in blood pressure, especially in older people. [2]
"No-flush" niacin. A 2013 trial of 120 adults with mildly to moderately raised cholesterol compared a wax-matrix extended-release niacin and "no-flush" inositol hexanicotinate at 1,500 mg a day for 6 weeks. Inositol hexanicotinate was well tolerated but did no better than placebo on blood lipids, and in a small substudy of five people it showed no evidence of bioavailability. [5] Other "no-flush" products: Proper evidence not found; we searched PubMed for trials of inositol hexanicotinate and found only this comparison.
Liver safety
The NHS says taking high doses of nicotinic acid for a long time could lead to liver damage. [1] MedlinePlus lists liver damage, raised blood sugar, peptic ulcers and skin rashes among effects of too much niacin. [3] EFSA says the more severe forms of nicotinic acid toxicity occur principally above 500 mg a day, and that liver toxicity occurs at doses about ten times higher than those that cause flushing. [2]Formulation matters. A pharmacy review describes three forms of niacin: immediate-release, sustained-release and extended-release. It says flushing is most often seen with immediate-release products and liver toxicity with sustained-release ones, and links both to how fast niacin is absorbed. [6] We tried to read the NCBI LiverTox entry on niacin, but the page was behind a browser check, which we did not bypass. A regulator statement comparing over-the-counter niacin supplements with prescription niacin: Proper evidence not found in the pages we could read. Read the label and ask a pharmacist which form a product contains.
Niacin for cholesterol: what trials found
MedlinePlus says large doses of niacin can modestly raise "good" HDL cholesterol and lower triglycerides, and to talk to a clinician before starting any supplement. [3] The key question is whether that changes heart attacks and strokes.| Study | What it tested | What it found |
|---|---|---|
| AIM-HIGH (2011) | 3,414 people with heart disease and well-controlled LDL: extended-release niacin 1,500 to 2,000 mg a day or placebo, all on simvastatin. | Stopped after about 3 years for lack of efficacy. Events: 16.4% niacin vs 16.2% placebo. HDL rose and triglycerides fell. [7] |
| HPS2-THRIVE (2014) | 25,673 adults with vascular disease: 2 g extended-release niacin with laropiprant, or placebo, on statin-based therapy. | No significant reduction in major vascular events (13.2% vs 13.7%). More serious side effects, including disturbed diabetes control, stomach and gut problems, infection and bleeding. [8] |
| Cochrane review (2017) | 23 trials, 39,195 people; median niacin dose 2 g a day. | Moderate- to high-quality evidence that niacin does not reduce death, heart attacks or strokes. People on niacin were more likely to stop because of side effects. [9] |
Biomarker change (HDL, triglycerides) did not translate into fewer events in these trials. These results apply to people with existing vascular disease on statins and to doses far above vitamin amounts. They do not tell us about niacin for people without heart disease: Proper evidence not found in the trials above. See vitamin supplements and heart disease evidence.
Official intake levels
| Body and year | Population and form | Amount |
|---|---|---|
| US RDA via MedlinePlus (reviewed 2025) | Males 14 and older / females 14 and older | 16 / 14 mg a day; pregnancy 18 mg; lactation 17 mg [3] |
| NHS, UK (2020) | Adults | About 16.5 mg men, 13.2 mg women a day [1] |
| NHS, UK (2020): supplements unlikely to cause harm | Nicotinic acid / nicotinamide | 17 mg or less / 500 mg or less a day [1] |
| EFSA, EU (2002 opinion) | Adults, nicotinic acid | Upper limit 10 mg a day; not applicable in pregnancy or breastfeeding because of inadequate data [2] |
| EFSA, EU (2002 opinion) | Adults, nicotinamide | Upper limit about 900 mg a day; not applicable in pregnancy or breastfeeding [2] |
| Health Canada DRI table (page dated 2025) | Adults 19 to 50, synthetic forms from supplements and fortified foods | Upper limit 35 mg a day (niacin equivalents) [10] |
EFSA's nicotinic-acid limits for children by age are 2 mg (1 to 3 years), 3 mg (4 to 6), 4 mg (7 to 10), 6 mg (11 to 14) and 8 mg (15 to 17) a day. [2] The cholesterol-treatment amounts in the trials above are far higher than any of these figures. See RDA, AI, DV and UL.
Precautions
- Prescription niacin: if a clinician prescribed it, please keep taking it as directed and ask them about any questions. Do not stop or change it on your own.
- Statins and other medicines: the large trials above gave niacin together with statins. See medication interactions. The NHS and MedlinePlus niacin pages we read do not list niacin-medicine interactions, so ask a pharmacist.
- Diabetes and blood sugar: MedlinePlus lists raised blood sugar as an effect of too much niacin, and HPS2-THRIVE found more serious diabetes-control problems. [3] [8]
- Liver disease or heavy alcohol use: talk to your clinician before any high-amount niacin; see liver safety. MedlinePlus advises avoiding hot drinks and alcohol with niacin to reduce flushing. [3]
- Pregnancy and breastfeeding: no EFSA upper limit applies because data are inadequate. [2] Ask your midwife or doctor: pregnancy and breastfeeding.
- Before surgery: tell the surgical team about all supplements: surgery and procedures.
- Product quality: see quality testing and certifications.
Related
Niacin profile · NAD precursors · The eight B vitaminsFrequently asked questions
Is the niacin flush dangerous?
EFSA described flushing as a minor health effect but used it to set the European limit because of concerns about brief blood-pressure drops, especially in elderly people. [2] Ask a clinician if flushing is severe or you feel faint.
Does niacin lower the risk of heart attack?
Not when added to statins in large trials. A Cochrane review found it did not reduce heart attacks or deaths. [9] HDL and triglycerides improved in AIM-HIGH, but events did not fall. [7]
Can niacin hurt the liver?
Yes, at high amounts. The NHS and MedlinePlus both list liver damage with high intakes. [1] [3] Sustained-release products have been linked to liver toxicity in a pharmacy review. [6]
Is niacinamide the same as niacin?
It is a different form of vitamin B3. EFSA says nicotinamide does not cause the flushing response. [2] See the comparison page.
Is "no-flush" niacin as good as niacin?
For cholesterol, one trial found inositol hexanicotinate no better than placebo. [5] Proper evidence not found for other "no-flush" products.
References
- NHS (UK). Vitamins and minerals: B vitamins and folic acid. Page last reviewed 3 August 2020. Read 2026-10-23.
- European Food Safety Authority. Tolerable Upper Intake Levels for Vitamins and Minerals, February 2006 (Scientific Committee on Food opinions: vitamin B6 expressed 19 October 2000; niacin 17 April 2002). Read 2026-10-23.
- MedlinePlus Medical Encyclopedia (US National Library of Medicine). Niacin. Review date 1/21/2025. Read 2026-10-23.
- Kamanna VS, Ganji SH, Kashyap ML. The mechanism and mitigation of niacin-induced flushing. Int J Clin Pract 2009;63(9):1369-77. PMID 19691622. Read 2026-10-23.
- Keenan JM. Wax-matrix extended-release niacin vs inositol hexanicotinate: a comparison of wax-matrix, extended-release niacin to inositol hexanicotinate "no-flush" niacin in persons with mild to moderate dyslipidemia. J Clin Lipidol 2013;7(1):14-23. PMID 23351578. Read 2026-10-23.
- Pieper JA. Understanding niacin formulations. Am J Manag Care 2002;8(12 Suppl):S308-14. PMID 12240702. Read 2026-10-23.
- AIM-HIGH Investigators. Niacin in patients with low HDL cholesterol levels receiving intensive statin therapy. N Engl J Med 2011;365(24):2255-67. PMID 22085343. Read 2026-10-23.
- HPS2-THRIVE Collaborative Group. Effects of extended-release niacin with laropiprant in high-risk patients. N Engl J Med 2014;371(3):203-12. PMID 25014686. Read 2026-10-23.
- Schandelmaier S, et al. Niacin for primary and secondary prevention of cardiovascular events (Cochrane review). Cochrane Database Syst Rev 2017;6:CD009744. PMID 28616955. Read 2026-10-23.
- Health Canada. Dietary reference intakes tables: Reference values for vitamins. Page dated 2025-11-19. Read 2026-10-23 through a web-fetch tool.