BMJ Group Medical Reference
Niacin is one of the B vitamins. It is also called nicotinic acid. Niacin is one of the oldest treatments for high cholesterol, but it's not used much now, because it can cause side effects, such as itching, flushing (a red face), and diarrhoea.
But your doctor might suggest you take niacin if you are taking a newer treatment and your cholesterol is still high, or if you can't take other kinds of treatment. Niacin comes as tablets called Niacor.
Some research shows that niacin can lower cholesterol and also triglyceride levels.  But many of the people who took part in this research were also taking a statin to lower their cholesterol. We don't know whether taking niacin helps lower your risk of having a heart attack or a stroke.
The most common side effect of taking niacin is flushing. Taking niacin raised people's average blood sugar, but only very slightly.
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