The "best" niacin supplement depends entirely on why you are taking it: Niacin vs. Nicotinamide vs. Niacinamide - Purovitalis

If you’re looking to buy Vitamin B3 (niacin), it’s vital to understand that "niacin" is an umbrella term for several distinct chemical forms, each serving a different health purpose. Choosing the wrong one can lead to an uncomfortable (though usually harmless) skin reaction or, more importantly, failing to achieve your specific health goals. Choosing the Right Form