Although the RDA for niacin (vitamin B3) is based on caloric intake, an intake of at least 18 milligrams per day is recommended by most authorities. However, additional niacin has been shown to exert a favorable effect on many health conditions. Supplemental niacin is available as either nicotinic acid or niacinamide. Each form has different applications. In the nicotinic acid form, niacin is an effective agent for lowering blood cholesterol levels, while in the niacinamide form, niacin is useful in treating arthritis. In the field of orthomolecular psychiatry, large doses of niacin, in the form of nicotinic acid or niacinamide, are often utilized in the treatment of schizophrenia. Doses in excess of 50 milligrams of niacin as nicotinic acid produce a transient flushing of the skin. However, high doses - two to six grams per day - of either nicotinic acid or niacinamide should be monitored by a physician as they may result in liver disorders, peptic ulcers, and glucose intolerance.