Niacin is a form of vitamin B3 made in the body from tryptophan. It's found in many foods including meat, fish, milk, eggs, green vegetables, and cereals.

Niacin is required for the proper function of fats and sugars in the body and to maintain healthy cells. At high doses, niacin might help people with heart disease because of its effects on blood clotting. It might also improve levels of fats called triglycerides in the blood.

People use niacin supplements for metabolic syndrome, heart disease, cataracts, high blood pressure, abnormal cholesterol levels, vitamin B3 deficiency, pellagra and many other conditions.