How Much Niacin Causes Flushing? Flushing usually occurs after taking 30 to 50 milligrams (mg) or more of nicotinic acid. When taken in higher doses of 1,000 to 3,000 mg per day, nicotinic acid ...

Taking niacin on an empty stomach increases side effects (such as flushing, upset stomach). Follow all directions on the product package. If your doctor has prescribed this medication, take it as ...