Niacin (Vitamin B3): Nicotinic Acid, Nicotinamide and Niacinamide
Niacin (vitamin B3): nicotinic acid versus nicotinamide (niacinamide), food sources, intake levels by country, pellagra, flushing and liver cautions, and what cholesterol trials found.
Content last updated . This page has not been medically reviewed.
What is Vitamin B3 (niacin) good for?
What the body uses it for, and how strong the evidence is. A normal job in the body is not proof that extra supplements add benefit; each card says which.
Releasing energy from food
Established roleNiacin helps the body release energy from the food we eat.
Supplements: Supplements are not shown to add energy in people who already get enough.
Keeping the nervous system healthy
Established roleNiacin helps the nervous system stay healthy.
Supplements: Supplements correct a lack; no good evidence of extra benefit when intake is adequate.
Keeping skin healthy
Established roleNiacin helps keep skin healthy; a severe lack causes scaly, inflamed skin.
Supplements: Supplements correct a lack; not shown to improve skin otherwise.
Helping the digestive system work
Established roleNiacin helps the digestive system work normally.
Supplements: Supplements correct a lack; no read source shows extra digestive benefit.
Preventing and treating pellagra
Deficiency linkPellagra is the disease of too little niacin, causing digestive problems, skin sores and mental confusion.
Supplements: Niacin treatment is directed by a clinician; rare in the United States.
Changing blood fats at medicine-level doses
Preliminary or mixedLarge doses of nicotinic acid can modestly raise HDL cholesterol and lower triglycerides.
Supplements: Blood-test change only; heart outcome benefit not verified from sources read in this pass. Needs clinician guidance.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Health goals (4)
- Blood Sugar BalanceDocumented risk
Too much niacin can raise blood glucose, so people with diabetes should ask a clinician before high doses.
- Cholesterol BalancePreliminary or mixed
Large medicine-level doses of nicotinic acid can modestly raise HDL and lower triglycerides, but this is a blood-test change; it is not an effect of normal intake, and it often causes flushing. Ask a clinician first.
- Digestive SupportEstablished role
Niacin helps the digestive system work, and a severe lack causes diarrhoea and abdominal pain. This is about getting enough, not about extra supplements.
- Healthy SkinEstablished role
Niacin helps keep skin healthy, and a severe lack causes inflamed, scaly skin (pellagra). Extra supplements have not been shown to improve skin in people who get enough.
Body systems (7)
- Nervous SystemEstablished role
Niacin helps keep the nervous system healthy. Untreated severe deficiency can cause nerve damage and mental confusion.
- Digestive SystemEstablished role
Niacin helps the digestive system work; deficiency causes diarrhoea, abdominal pain and inflamed mucous membranes.
- Hepatic / Liver SystemDocumented risk
Long-term high doses of niacin could damage the liver (NHS; MedlinePlus lists liver damage with too much).
- Integumentary SystemEstablished role
Niacin helps keep skin healthy; deficiency causes scaly sores, mainly on sun-exposed skin.
- Liver & DetoxDocumented risk
Niacin does not detoxify the liver; the documented link is that long-term high doses can harm it.
- Skin, Hair & BeautyEstablished role
Niacin supports skin health (NHS, MedlinePlus). No source read links it to hair, and extra supplements are not shown to improve skin when intake is adequate.
- Energy & FatigueEstablished role
Niacin helps the body release energy from food. That is a normal role, not proof that supplements reduce tiredness in people who get enough.
Body parts (4)
- Nervous SystemEstablished role
Niacin helps keep the nervous system healthy; severe untreated deficiency can damage nerves, particularly in the brain.
- SkinDeficiency link
Pellagra causes inflamed, scaly skin sores mainly on sun-exposed skin; niacin treats it.
- GutDeficiency link
Niacin helps the digestive system work; deficiency causes diarrhoea, abdominal pain and loss of appetite.
- LiverDocumented risk
Long-term high doses could lead to liver damage.
Functional actions (3)
- Digestive SupportEstablished role
Niacin helps the digestive system work normally.
- Energy ProductionEstablished role
Niacin helps the body release energy from food. This is a normal role; supplements are not shown to add energy when intake is adequate.
- Nervous System SupportEstablished role
Niacin helps keep the nervous system healthy.
Root causes (4)
- Nutrient DeficiencyDeficiency link
Too little niacin (or tryptophan) causes pellagra.
- Digestive DysfunctionDeficiency link
Gastrointestinal disease and weight-loss surgery can reduce absorption and lead to pellagra.
- Poor DietDeficiency link
Diets low in niacin or tryptophan, especially heavy in untreated corn, can lead to pellagra.
- Medication Side EffectsDeficiency link
Some medicines (isoniazid, 5-fluorouracil, azathioprine) are listed as possible causes of pellagra. Conversely, high-dose niacin itself can cause side effects.
Habits (1)
- Balanced NutritionDeficiency link
A well-balanced diet prevents pellagra; niacin is found in meat, fish, eggs, milk, cereals, legumes and peanuts.
Biomarkers (3)
- Blood GlucoseDocumented risk
Too much niacin can raise blood glucose.
- HDL CholesterolPreliminary or mixed
Large doses can modestly raise HDL. This is a lab-value change, not proof of health benefit.
- TriglyceridesPreliminary or mixed
Large doses can lower blood triglycerides. This is a lab-value change, not proof of health benefit.
Conditions & symptoms (8)
- FlushingDocumented risk
High-dose nicotinic acid commonly causes skin flushing.
- Drug-Induced Liver DiseaseDocumented risk
Long-term high doses of niacin could lead to liver damage.
- HyperglycemiaDocumented risk
Too much niacin can raise blood glucose.
- Alcohol Use DisorderDeficiency link
Heavy alcohol use is listed as a risk factor for pellagra.
- Anorexia NervosaDeficiency link
Anorexia is listed as a risk factor for pellagra.
- HyperlipidemiaPreliminary or mixed
Niacin is given at high doses to treat high cholesterol and can modestly change HDL and triglycerides; this is a clinician-led treatment, and benefit for heart outcomes was not verified here.
- Malignant Carcinoid SyndromeDeficiency link
Carcinoid syndrome is listed as a risk factor for pellagra.
- Peptic UlcerDocumented risk
Too much niacin can cause peptic ulcers.
Documented risks and interactions (2)
- Flushing at high doses. High-dose nicotinic acid can cause warmth, redness, itching or tingling of the face, neck, arms or chest.
- Liver, blood sugar and stomach risks at high doses. Too much niacin can damage the liver, raise blood glucose, and cause peptic ulcers and skin rashes.
Overview
Niacin is vitamin B3. The NHS says it helps the body release energy from food and keeps the nervous system and skin healthy. [1] MedlinePlus says it helps the digestive system, skin and nerves work and is important for changing food to energy. [2] Like the other B vitamins it is water soluble and not stored in the body in large amounts. [2]High-dose niacin is a medicine-level decision. It can cause flushing and, over time, liver damage, and large trials of niacin for heart disease did not show a benefit. Do not start high-dose niacin without talking to a clinician or pharmacist. [1][3]
Forms: nicotinic acid and nicotinamide
The NHS says there are 2 forms of niacin, nicotinic acid and nicotinamide, and that both are found in food. [1] MedlinePlus uses the names nicotinamide and niacinamide together when it describes the supplement form that did not appear to cause side effects. [2] The two forms are treated differently at high intakes: the NHS and EFSA each give separate supplement limits for them (see the table). [1][4] Niacinamide is also used in some skin products; those are outside this page, see vitamins for skin, hair and nails. For the side-by-side, see niacin vs niacinamide vs nicotinic acid.Food sources
The NHS lists meat, fish, wheat flour and eggs. [1] MedlinePlus lists milk, eggs, enriched breads and cereals, rice, fish, lean meats, legumes, peanuts and poultry. [2] See foods high in biotin, thiamin, riboflavin, niacin, B6 and pantothenic acid.Official intake levels
Published levels for the groups named, not personal advice. Units differ between sources, so do not compare figures across rows without checking the unit. See RDA, AI, DV and UL.| Body, country and year | Group | Level |
|---|---|---|
| NHS, UK, page reviewed 2020 | Adults, men / women | About 16.5 mg / 13.2 mg a day [1] |
| US Dietary Reference Intakes, as listed by MedlinePlus (review 2025) | Males 14 and older / females 14 and older | RDA 16 mg / 14 mg a day; females 18 mg in pregnancy and 17 mg in lactation [2] |
| Health Canada, table dated 2025 | Adults 19 to 30, males / females | RDA 16 / 14 mg niacin equivalents (NE) a day; upper level 35 mg a day for preformed niacin (nicotinic acid and nicotinamide) from supplements and fortified foods [5] |
| EFSA, EU, overview version 2025 (limits set by the Scientific Committee on Food, 2002) | Adults | Upper level 10 mg a day for nicotinic acid and 900 mg a day for nicotinamide [4] |
| NHS, UK, 2020 | Supplement guidance for adults | 17 mg or less a day of nicotinic acid, or 500 mg or less of nicotinamide, is unlikely to cause harm [1] |
| Daily Value on US labels (FDA, 2024) | Label reference only | 16 mg NE [6] |
The upper levels apply to supplements and fortified foods, not to niacin in ordinary food. [5]
Deficiency: pellagra
Established. A lack of niacin causes pellagra, with digestive problems, inflamed skin and poor mental function. [2] MedlinePlus says pellagra comes from too little niacin or tryptophan (an amino acid) in the diet or from poor absorption, and can follow gastrointestinal disease, weight-loss surgery, anorexia, excessive alcohol use or certain medicines. It is rare in the United States. Untreated, it can cause nerve damage and death. [7]Treatment is led by a clinician, who may check urine and blood and prescribe niacin and treat the underlying cause. [7] Do not self-diagnose from skin or digestive symptoms.
What research shows for specific uses
| Question | What the source found | Label |
|---|---|---|
| Raising HDL or lowering triglycerides at large doses | MedlinePlus says large doses can modestly raise HDL cholesterol and lower triglycerides and tells readers to talk to their provider first. [2] | Biomarker change only |
| Preventing heart attacks, strokes or death | A 2017 Cochrane review of 23 trials (39,195 people; median niacin dose 2 g a day) found no reduction in mortality, heart attacks or strokes and more stopping due to side effects. [3] | No good evidence of benefit |
| Niacin added to statin therapy | The AIM-HIGH trial (3,414 people with heart disease, extended-release niacin 1,500 to 2,000 mg a day) was stopped for lack of efficacy: no extra clinical benefit despite better HDL and triglyceride levels. [8] | No good evidence of benefit |
| Safety in a very large trial | HPS2-THRIVE (25,673 adults, 2 g extended-release niacin with laropiprant) found no significant reduction in major vascular events, and more serious problems with diabetes control, the gut, muscles, skin, infection and bleeding. [9] | Evidence of harm at these amounts |
These are study amounts in people with vascular disease or at risk, and the 2 g-a-day amounts are far above the intake levels above. They do not apply to niacin from food.
Testing
Doctors may test urine and blood when pellagra is suspected. [7] Proper evidence not found for a routine niacin test for healthy people. See deficiency testing and its limits.Related
All vitamins · Understanding vitamins · B-complex productsFrequently asked questions
What is the difference between niacin and niacinamide?
Niacin is the group name; the two forms are nicotinic acid and nicotinamide. Nicotinic acid causes flushing at high doses. [1][2]
Does niacin lower cholesterol?
Large doses change HDL and triglycerides, but trials found no reduction in heart attacks, strokes or deaths. [2][3]
What causes niacin flush?
High doses of nicotinic acid can cause skin flushing. [1]
Can niacin damage the liver?
The NHS says high doses taken for a long time could. [1] Talk to a clinician before high-dose products.
What is pellagra?
The deficiency disease from too little niacin or tryptophan; it is rare in the United States and is treated by a clinician. [7]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
How to read the evidence labels
Labels used on this page: established nutritional role / deficiency treatment, no good evidence of benefit, evidence of harm and marketing claim. "Proper evidence not found" means we searched the sources named and found nothing usable.
Safety and precautions
- Flushing: the NHS says high doses of nicotinic acid can cause skin flushes. [1] MedlinePlus describes flushing as warmth, redness, itching or tingling of the face, neck, arms or upper chest. [2] Detail: niacin flush, high-dose niacin and liver safety.
- Liver: the NHS says high doses taken for a long time could lead to liver damage. [1] MedlinePlus also lists raised blood sugar, peptic ulcers and skin rashes with too much niacin. [2] People with liver disease, diabetes or stomach ulcers should ask a clinician first. See vitamins and kidney or liver disease.
- Nicotinamide: the NHS says there is not enough evidence on high daily doses, while MedlinePlus says nicotinamide or niacinamide supplements do not appear to cause side effects. The sources differ, so treat high amounts with caution. [1][2]
- Medicines: niacin is often used alongside statins in trials, but Proper evidence not found in the pages we read for a complete interaction list (NIH Office of Dietary Supplements pages were blocked). See medication interactions; tell your pharmacist about every supplement.
- Pregnancy and children: the US RDA is higher in pregnancy and lactation and lower for children. [2] Ask your care team before supplements.
- Before surgery: Proper evidence not found specific to niacin; see vitamins before surgery.
- Quality: see quality testing and certifications.
References
- NHS (UK). B vitamins and folic acid. Page last reviewed 3 August 2020. Read 2026-10-23.
- MedlinePlus Medical Encyclopedia (US National Library of Medicine). Niacin. Review date 1/21/2025. Read 2026-10-23.
- Schandelmaier S, Briel M, Saccilotto R, et al. Niacin for primary and secondary prevention of cardiovascular events. Cochrane Database Syst Rev 2017;6:CD009744. Read 2026-10-23.
- European Food Safety Authority. Overview on Tolerable Upper Intake Levels as derived by the Scientific Committee on Food (SCF) and the EFSA NDA Panel, version 1, August 2025. Read 2026-10-23 (text extracted from the PDF; table layout reconstructed).
- Health Canada. Dietary reference intakes tables: Reference values for vitamins. Page dated 2025-11-19. Read 2026-10-23 through a web-fetch tool, which returned the tables as a text summary; direct download was blocked.
- US Food and Drug Administration. Daily Value on the Nutrition and Supplement Facts Labels. Content current as of 03/05/2024. Read 2026-10-23.
- MedlinePlus Medical Encyclopedia (US National Library of Medicine). Pellagra. Review date 10/27/2024. 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. 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. Read 2026-10-23.