Is niacin okay for people with diabetes?

Whenever I diagnose a patient with a new health problem, I make sure to ask him or her about the medications he or she is currently using—prescription, over-the-counter, and herbal. As the below question and answer, first published in the Harvard Heart Letter, outlines, a change in health status is a good time to review whether your medications need to change, too. 

Q. I have been taking niacin for several years, and it has helped keep my good and bad cholesterol in their healthy ranges. Now I have been diagnosed with diabetes, and my doctor forbids me from taking niacin any more. What's the reasoning behind this?

A. Niacin is one of the oldest drugs for treating cholesterol problems. Not only does it lower LDL (bad) cholesterol and triglycerides, but it is also the best medication for increasing HDL (good) cholesterol.

In the mid-1980s, a few small studies showed that high doses of niacin increased blood sugar levels among people with diabetes or prediabetes. This work prompted the American Diabetes Association to recommend that the drug be used cautiously, at doses under 2 grams a day, and with frequent blood sugar monitoring. Many doctors took this to mean that niacin shouldn't be used by people with diabetes.

Since then, two large trials have shown that niacin has only small, if any, effects on either blood sugar or hemoglobin A_1C, a kind of time-lapse test that gauges blood sugar levels over the previous three months. One of these trials used over-the-counter crystallized niacin; the other, a once a day prescription version.

As your doctor probably told you, being diagnosed with diabetes vaults you up a notch when it comes to cardiovascular risk. In fact, we now consider diabetes to be on a par with angina or other forms of heart disease when it comes to calculating the risk of having a heart attack. Since there is overwhelming evidence that statins lower not only LDL but the chances of having a heart attack or dying from heart disease, they are the first choice for cholesterol problems among people with diabetes.

But high LDL isn't the only problem for many people with diabetes or prediabetes — they often have the constellation of high LDL, low HDL, and high triglycerides. For those who continue to have low HDL and/or high triglycerides after starting a statin, adding niacin is a good option. There is some preliminary evidence that adding niacin to a statin offers additional cardiovascular benefits; this is being tested in a large study. People who can't tolerate a statin because of side effects can use niacin alone.

Some people have trouble taking niacin because of the uncomfortable flushing the drug often causes. A once a day, extended-release preparation available by prescription only (Niaspan) helps limit this side effect. Research is also underway on a pill that combines niacin with a drug called MK-0524A that blocks the release of prostaglandin D₂, the substance largely responsible for the flushing effect.

Whenever I prescribe niacin for one of my patients with diabetes, I monitor his or her blood sugar and hemoglobin A_1C carefully for several months, just to be on the safe side. A small increase in blood sugar can usually be controlled by changing the dose of insulin or other medications. If not, or if there is a significant jump in blood sugar, niacin can be replaced with a fibrate or other medications.

Ask your doctor to rethink his or her stance on niacin. The American Diabetes Association now recommends its use by people who have low HDL. With a little extra attention to blood sugar, this drug may help people with diabetes improve their cholesterol levels and help prevent an all too common consequence of diabetes — heart disease

— Om P. Ganda, MD
Associate Clinical Professor of Medicine
Joslin Diabetes Center
Harvard Medical School

Julie K. Silver, M.D., is an assistant professor in the Department of Physical Medicine and Rehabilitation at Harvard Medical School. She is also the Chief Editor of Books for Harvard Health Publications.

Heart Letter
The Harvard Heart Letter provides eight pages of monthly heart news, directly from the more than 8,000 doctors and researchers at Harvard Medical School. It's a source of expert advice for people who may already suffer from heart disease (or their family members) and for people concerned about their risk who wish to take steps towards positive change.

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