DESC: Niacin [Circulatory, Nervous]. Niacin is important to both the circulatory and nervous systems. The body's energy system also requires niacin for proper function. Each tablet contains 250 mg of non flushing niacin, which is 1,250 percent of the Daily Value. It is combined in a base of hops flowers and feverfew herb. For best results, take niacin in conjunction with other B vitamins.