Niacin overdose: What are the symptoms?

I take niacin to treat my high cholesterol, but I've heard that if you take too much it can be harmful. Should I be concerned?

- No name / No state given

Mayo Clinic cardiologist Gerald Gau, M.D., and colleagues answer select questions from readers.

Answer

Niacin overdose is unlikely if you take niacin only in the amount prescribed by your doctor. In recommended doses, niacin is an effective treatment for high cholesterol, high blood fats (lipids) and niacin deficiency.

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

Signs and symptoms of a niacin overdose include:

Rapid heartbeat
Skin flushing
Itching
Nausea and vomiting
Abdominal pain
Severe liver damage (hepatoxicity)

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