Mayo Clinic Health Library

Question

Niacin overdose: What are the symptoms?

I take niacin to treat my high cholesterol. Should I be concerned about a potential niacin overdose?

Updated: 07-08-2011

Answer

Niacin overdose is unlikely if you take niacin only in the amount prescribed by your doctor. In recommended doses, prescription-strength niacin is an effective treatment for high total cholesterol, high blood fats (lipids) and niacin deficiency. While it's not possible to overdose on niacin simply by eating too many niacin-rich foods, taking too much over-the-counter or prescription niacin can be dangerous.

You may have heard that too much niacin can be harmful because of Internet rumors. The rumors falsely state that by taking a large amount of niacin, people can flush the chemicals that show they've used marijuana out of their bodies before they take a drug test. No studies have shown that niacin can do this, and this can be very dangerous because it may lead to niacin overdose.

Niacin overdose symptoms include:

  • Severe skin flushing combined with dizziness
  • Rapid heartbeat
  • Itching
  • Nausea and vomiting
  • Abdominal pain
  • Diarrhea
  • Severe liver damage (hepatoxicity)

If you're concerned about a potential niacin overdose, talk to your doctor to make sure you're taking the correct amount. If you think you may have overdosed, seek medical attention immediately.