Niacin and Flushing

Q:  What is it about niacin that causes intense flushing and heat in the body?

A:  Before I answer your question about niacin, let me just briefly touch on its uses. Niacin is a B vitamin which can lower LDL cholesterol (the bad kind) and raise HDL cholesterol (the good kind). It has been shown to lower rates of heart attack and death in people who have coronary artery disease.

To be effective, high doses are required - 2000-6000 mg per day. At these high doses, side effects such as nausea and flushing are common. Niacin can also worsen gout and raise the blood sugar in diabetics.

Flushing is one of the most troublesome effects of niacin. Niacin stimulates prostaglandin (a hormone that affects many different body functions), which causes blood vessels to abruptly dilate and fill with blood - hence the flushing and sometimes even a light-headed feeling. NSAIDs like aspirin and ibuprofen interfere with prostaglandin function, so taking one about 1/2 to one hour before the niacin may help.

Niacin is available over-the-counter in regular and time-release forms. Some patients find that they experience less flushing with the time-release preparation. The latter are more expensive, however, and carry a slightly higher risk of liver toxicity. In addition, many vitamin companies sell "no-flush" niacin (inositol hexanicotinate) that might be appropriate for some people.

"Dear Doctor" is a compilation of patient questions answered by doctors from the Medical College of Wisconsin.