What is niacin?

Niacin (nicotinic acid) is a B vitamin that's used by your body to turn food into energy. Niacin also helps keep your nervous system, digestive system and skin healthy. That's why niacin is often a part of a daily multivitamin, though most people get enough niacin from the food they eat.

When it's used as a treatment to increase your HDL cholesterol or correct a vitamin deficiency, niacin is sold in higher doses that are prescribed by your doctor. Prescription-strength niacin includes such drugs as Niacor and Niaspan.

Niacin is also available as an over-the-counter supplement. Supplements sold over-the-counter are not regulated like prescription medications. The ingredients, formulations and effects of over-the-counter niacin can vary widely.

Don't take niacin without discussing it with your doctor first because niacin can cause serious side effects when taken in high doses.