No-flush niacin is often inositol hexanicotinate. Each molecule of it breaks down slowly into six molecules of niacin. Niacin is Vitamin B3. It's hard to imagine a vitamin could be dangerous but I suppose anything taken in excess can be toxic. Using no-flush suggests you might need a lower dose to achieve its cholesterol-lowering effect. I'm taking it now, along with pantothenic acid. Eventually I'll have the cholesterol rechecked. If the levels have come down, I'll lower to amount of both medications.