Get emergency medical help if you have signs of an allergic reaction to niacin: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
a light-headed feeling, like you might pass out;
irregular heartbeats;
severe warmth or redness under your skin;
vision problems; or
jaundice (yellowing of the skin or eyes).
Common niacin side effects may include:
flushing (sudden warmth, redness, or tingly feeling);
upset stomach, vomiting, diarrhea;
abnormal liver function tests;
itching, dry skin;
cough;
skin discoloration; or
headache.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Niacin side effects (more detail)
