What is Vitamin B3 (niacin) and what does it do?

Vitamin B3 includes nicotinic acid and niacinamide. It helps the body make NAD and NADP, which are essential for energy metabolism, DNA repair, and many cellular reactions.

What are the symptoms of niacin deficiency?

Severe deficiency can cause pellagra, classically associated with dermatitis, diarrhea, and cognitive or neurological changes. Deficiency is uncommon with a varied diet but can occur with poor intake or malabsorption.

How much niacin do adults need per day?

Typical recommended intakes for adults are about 14–16 mg per day, depending on sex and life stage. Needs may differ during pregnancy, breastfeeding, or certain medical conditions.

Is niacin used to manage cholesterol?

High-dose nicotinic acid can affect blood lipids, including raising HDL and lowering triglycerides. Because side effects and interactions are possible, lipid use should be done under medical supervision.

What are common side effects of niacin supplements?

Nicotinic acid can cause flushing, warmth, itching, and stomach upset, especially at higher doses. High doses can also affect liver function and blood sugar, so monitoring may be needed.

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Vitamin B

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Vitamin B3
(Niacin)

Strong study situation·10/10

A higher score indicates better study conditions, but not necessarily effectiveness.

Vitamin B3 (niacin) is an essential water-soluble vitamin critical for metabolism, skin, and nerve health, and is used at high doses for lipid management under medical supervision.

Cognitive Enhancement Essential Nutrient Skin Health Neuroprotective Cholesterol Management

dose range

14–16 mg

Once daily with food

Consumption

Take with meals to improve absorption and minimize flushing; therapeutic doses only under medical supervision.

Not fat-soluble.

Best time

Divide high doses for lipid treatment as directed by a doctor; routine intake is typically at breakfast or the first meal.

Description

Vitamin B3, or niacin, includes nicotinic acid and niacinamide forms. It is vital for energy metabolism, DNA repair, and cellular health, and prevents the deficiency disease pellagra. While commonly obtained from diet, niacin’s high-dose form is sometimes used as a cholesterol-lowering agent under supervision.

benefits

Main effects with level of evidence

Strong

Note on evidence

Niacin’s essential role in metabolism and pellagra prevention is well established; pharmacological benefits for lipids are recognized but must be weighed against risk in high doses.

Prevents Pellagra

Strong

Adequate niacin prevents pellagra, a potentially fatal deficiency disease marked by dermatitis, diarrhea, and dementia.

Particularly relevant for: General · At-risk populations (malnutrition, alcoholism)

6 · NIH Office of Dietary Supplements – Niacin Fact Sheet 4 · Harvard T.H. Chan – Niacin (Vitamin B3)8 · EFSA Scientific Opinion on Dietary Reference Values for Niacin

Supports Energy Metabolism

Strong

Niacin is a precursor to NAD and NADP, coenzymes needed for hundreds of reactions in energy production and cellular repair.

Particularly relevant for: General population · Older adults

6 · NIH Office of Dietary Supplements – Niacin Fact Sheet 4 · Harvard T.H. Chan – Niacin (Vitamin B3)8 · EFSA Scientific Opinion on Dietary Reference Values for Niacin

Cholesterol Management (Prescription, High Dose)

Moderate

Nicotinic acid, when prescribed in high doses, can increase HDL cholesterol, lower LDL cholesterol, and decrease triglycerides, though use is limited by side effects and requires medical oversight.

Particularly relevant for: Adults with dyslipidemia (under doctor care)

1 · Mayo Clinic – Niacin (Vitamin B3)6 · NIH Office of Dietary Supplements – Niacin Fact Sheet 7 · Cochrane Review: Niacin for Primary and Secondary Prevention of Cardiovascular Events

Skin Health

Moderate

Niacinamide (a form of B3) helps maintain the skin barrier, reduces inflammation, and may improve acne and rosacea.

Particularly relevant for: General · Individuals with skin conditions

2 · Healthline – Niacin: Benefits, Side Effects, Dosage, and Interactions 3 · WebMD – Niacin and Niacinamide (Vitamin B3)4 · Harvard T.H. Chan – Niacin (Vitamin B3)

Supports Nervous System and Cognitive Function

Limited

Niacin is essential for normal nervous system function; deficiency can cause neurological symptoms. Adequate intake supports cognitive health, though benefits of supplementation in non-deficient adults are less clear.

Particularly relevant for: General · Older adults

4 · Harvard T.H. Chan – Niacin (Vitamin B3)6 · NIH Office of Dietary Supplements – Niacin Fact Sheet

Safety & Information

Important safety information & known risks

For educational purposes only • not medical advice

Niacin is safe at recommended dietary intakes but can cause flushing and, at high doses, serious side effects including liver toxicity, GI symptoms, and worsened gout or peptic ulcer disease.

warning notices

Flushing (especially with nicotinic acid), GI upset, and, at high doses, potential liver toxicity and hyperglycemia.
Niacinamide is generally better tolerated and does not cause flushing.
Therapeutic high-dose use should be guided by a physician.
Avoid high-dose niacin (500 mg or more daily) unless prescribed, as it can cause severe flushing, liver injury, and worsen peptic ulcers or gout.
Use caution and monitor liver enzymes when using high-dose niacin or niacinamide supplements long-term.
Niacin can interact with statins and other cholesterol-lowering drugs, increasing the risk of side effects.
People with liver disease or active peptic ulcers should not use high-dose niacin.

Known interactions with medications

Statins
Antihypertensive drugs
Diabetes/insulin medications

Contraindications / special precautions

Active liver disease
Severe peptic ulcer disease
Gout

interactions

Important interactions between active ingredient ↔ supplement / medication / food

Niacin can interact with specific drugs and nutrients, especially at supplemental or pharmacological doses.

Niacin combined with statin drugs may increase risk of muscle and liver toxicity.

drug · Statins

CautionModerate

Why

Both agents can affect liver and muscle enzymes; risk of side effects is higher when used together for cholesterol lowering.

recommendation

Combination use should be closely monitored by a healthcare provider, with periodic liver enzyme tests.

1 · Mayo Clinic – Niacin (Vitamin B3)5 · MedlinePlus – Niacin 7 · Cochrane Review: Niacin for Primary and Secondary Prevention of Cardiovascular Events

Niacin may enhance the blood pressure–lowering effect of some medications.

drug · Blood pressure medications

MonitorLimited

Why

High-dose niacin can cause vasodilation, leading to additional blood pressure reduction with antihypertensives.

recommendation

Monitor blood pressure when combining niacin with antihypertensive drugs.

1 · Mayo Clinic – Niacin (Vitamin B3)5 · MedlinePlus – Niacin

High-dose niacin can raise blood sugar, affecting diabetes medication needs.

drug · Diabetes medications/insulin

MonitorLimited

Why

Niacin at high doses may cause or worsen hyperglycemia.

recommendation

Monitor blood sugar closely if taking niacin with diabetes medications; dose adjustments may be needed.

6 · NIH Office of Dietary Supplements – Niacin Fact Sheet 5 · MedlinePlus – Niacin

mechanisms of action

Brief explanations of how it works

NAD/NADP Coenzyme Synthesis

Niacin provides the precursor for NAD and NADP, which are essential for hundreds of metabolic reactions including energy production, DNA repair, and cell signaling.

6 · NIH Office of Dietary Supplements – Niacin Fact Sheet 4 · Harvard T.H. Chan – Niacin (Vitamin B3)8 · EFSA Scientific Opinion on Dietary Reference Values for Niacin

Lipid Modification (High-dose Nicotinic Acid)

At pharmacological doses, nicotinic acid reduces hepatic synthesis of very-low-density lipoprotein (VLDL), thereby lowering LDL and triglycerides and raising HDL.

7 · Cochrane Review: Niacin for Primary and Secondary Prevention of Cardiovascular Events 1 · Mayo Clinic – Niacin (Vitamin B3)6 · NIH Office of Dietary Supplements – Niacin Fact Sheet