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Niacinamide Side Effects

Medically reviewed by Last updated on Sep 17, 2023.

Applies to niacinamide: oral tablet extended release.

Serious side effects of Niacinamide

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, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Signs of high blood sugar like confusion, feeling sleepy, more thirst, more hungry, passing urine more often, flushing, fast breathing, or breath that smells like fruit.
  • Signs of liver problems like dark urine, feeling tired, not hungry, upset stomach or stomach pain, light-colored stools, throwing up, or yellow skin or eyes.
  • Muscle pain or weakness.
  • Chest pain or pressure.
  • Dizziness or passing out.
  • Shortness of breath.
  • Sweating a lot.

Other side effects of Niacinamide

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:

  • 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.
  • Itching.
  • Diarrhea.
  • Upset stomach or throwing up.
  • Cough.

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 1-800-332-1088. You may also report side effects at

For Healthcare Professionals

Applies to niacinamide: compounding powder, oral tablet.


Frequency not reported: Decrease in blood pressure, severe hypotension (increased fall risk)[Ref]


Frequency not reported: Impaired glucose tolerance, insulin resistance[Ref]

Nervous system

Frequency not reported: Headache, dizziness[Ref]


Frequency not reported: Nausea, heartburn, abdominal pain[Ref]


Frequency not reported: Skin flushing (with burning, tingling, and itching), rash[Ref]


Frequency not reported: Blurred or impaired vision, macular edema[Ref]


Liver toxicity occurred at intakes of 3000 mg/day.[Ref]

Frequency not reported: Liver toxicity[Ref]


Frequency not reported: Fatigue[Ref]


1. National Institutes of Health. Niacin. Fact Sheet for Health Professionals. 2020.

Further information

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.