Niacin (vitamin B-3) is an essential B-complex vitamin. Flush-free niacin contains inositol hexanicotinate, a form of niacin that consists of six molecules of niacin linked to a single inositol molecule. It is slowly broken down in the body to yield free niacin and inositol. This gradual release of niacin allows for true niacin activity without the characteristic niacin flush that many people cannot tolerate.

Inositol hexanicotinate is a compound formed by combining niacin (nicotinic acid) with inositol, a type of sugar alcohol that is similar to glucose. This combination is often used in dietary supplements as a form of niacin that is less likely to cause the flushing side effect associated with regular niacin supplementation.

Inositol hexanicotinate is believed to release niacin slowly in the body, which may help reduce the intensity or eliminate the flushing response. The theory is that the gradual release of niacin may allow the body to process it more efficiently, decreasing the likelihood of vasodilation (widening of blood vessels) near the skin's surface that leads to flushing.