Niacin, also known as nicotinic acid, is an essential water-soluble B vitamin (B3) that serves as a precursor to the coenzymes NAD and NADP, critical for cellular energy metabolism, DNA repair, and redox reactions. It occurs naturally in foods like meat, fish, and grains and is used therapeutically to treat dyslipidemia by lowering LDL cholesterol and triglycerides while raising HDL. Chemically, it is a pyridine derivative with a carboxylic acid group at the 3-position. It exhibits good stability under heat and light but can cause flushing at high doses due to prostaglandin-mediated vasodilation. Niacin is approved as a dietary supplement and food additive with GRAS status by the FDA.