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Niacinamide Side Effects

For the Consumer

Applies to niacinamide: oral tablet

What are some side effects that I need to call my doctor about right away?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Not able to eat.
  • A heartbeat that does not feel normal.
  • Black, tarry, or bloody stools.
  • Change in eyesight.
  • Not able to pass urine or change in how much urine is passed.
  • Yellow skin or eyes.
  • Muscle pain or weakness.
  • Swelling in the arms or legs.
  • Very bad numbness and tingling.
  • Very bad flushing.
  • Very upset stomach or throwing up.
  • Throwing up blood or throw up that looks like coffee grounds.

What are some other side effects of this drug?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

  • Headache.
  • Itching.
  • Loose stools (diarrhea).
  • Upset stomach.
  • Dizziness.
  • Feeling of warmth.
  • Flushing. Taking aspirin 30 minutes before taking this drug may help. If you wake up at night with flushing, get up slowly if you feel like passing out or you are dizzy.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-FDA-1088. You may also report side effects at

For Healthcare Professionals

Applies to niacinamide: compounding powder, oral tablet


Cardiovascular side effects are rare and mild and have included tachycardia.[Ref]


Metabolic side effects have included hyperglycemia and hyperuricemia.[Ref]

Nervous system

Nervous system side effects have included headache.[Ref]


Gastrointestinal side effects have included bloating, flatulence, diarrhea, stomach upset, and nausea.[Ref]


Dermatologic side effects have included increased sebaceous gland activity, dry skin, itching, and rash.[Ref]


1. Baumgartner TG, ed. "Clinical Guide to Parenteral Micronutrition." Gainsville, FL: Fujisawa (1991):

2. Sugar AM, Liu XP "Efficacy of voriconazole in treatment of murine pulmonary blastomycosis." Antimicrob Agents Chemother 45 (2001): 601-4

Some side effects of niacinamide may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

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