Niacin Side Effects

Medically reviewed by Drugs.com. Last updated on Jul 16, 2024.

Applies to niacin: oral capsule, oral capsule extended release, oral tablet, oral tablet extended release.

Serious side effects of niacin

Along with its needed effects, niacin may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking niacin:

Less common

• darkening of urine
• light gray-colored stools
• loss of appetite
• severe stomach pain
• yellow eyes or skin

Other side effects of niacin

Some side effects of niacin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common

• abdominal or stomach pain
• cough
• diarrhea
• feeling of warmth
• flushing or redness of the skin, especially on the face and neck
• headache
• nausea or vomiting
• rash or itching
• runny nose
• sneezing
• stuffy nose

Incidence not known

• dizziness or faintness
• dryness of the skin
• fever
• frequent urination
• joint pain
• muscle aching or cramping
• side, lower back, or stomach pain
• swelling of the feet or lower legs
• unusual thirst
• unusual tiredness or weakness
• unusually fast, slow, or irregular heartbeat

For healthcare professionals

Applies to niacin: compounding powder, oral capsule, oral capsule extended release, oral liquid, oral tablet, oral tablet extended release.

Cardiovascular

• Very common (10% or more): Flushing (i.e., warmth, redness, itching, and/or tingling) (up to 88%)
• Frequency not reported: Tachycardia, palpitations, atrial fibrillation, other cardiac arrhythmias, syncope, hypotension, postural hypotension^[Ref]

Dermatologic

• Common (1% to 10%): Rash, pruritus
• Frequency not reported: Sweating, skin burning sensation, maculopapular rash, dry skin
• Postmarketing reports: Skin discoloration^[Ref]

Gastrointestinal

• Very common (10% or more): Diarrhea (up to 14%), nausea (up to 11%)
• Common (1% to 10%): Vomiting
• Frequency not reported: Peptic ulcers, eructation, flatulence^[Ref]

Hematologic

• Postmarketing reports: Slight reductions in platelet counts, prothrombin time prolonged^[Ref]

Hypersensitivity

• Postmarketing reports: Hypersensitivity reactions (e.g., anaphylaxis, angioedema, urticaria, flushing, dyspnea, tongue edema, larynx edema, face edema, peripheral edema, laryngismus, vesiculobullous rash)^[Ref]

Hepatic

• Postmarketing reports: Hepatitis, jaundice^[Ref]

Metabolic

• Frequency not reported: Decreased glucose tolerance, gout^[Ref]

Musculoskeletal

• Frequency not reported: Myalgia, myopathy^[Ref]

Nervous system

• Frequency not reported: Dizziness, syncope
• Postmarketing reports: Migraine, asthenia, paresthesia^[Ref]

Ocular

• Postmarketing reports: Blurred vision, macular edema^[Ref]

Psychiatric

• Postmarketing reports: Insomnia, nervousness^[Ref]

Other

• Frequency not reported: Chills, edema^[Ref]

Respiratory

• Common (1% to 10%): Cough increased
• Frequency not reported: Dyspnea^[Ref]

Frequently asked questions

• How long does niacin stay in the human system?

Further information

Niacin side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

Medical Disclaimer