Niacin, also known as vitamin B3, is a water-soluble vitamin essential for the synthesis of NAD and NADP, coenzymes involved in cellular metabolism and energy production. Clinically, niacin is important for preventing pellagra, a condition characterised by dermatitis, diarrhoea, and dementia due to deficiency. Additionally, pharmacological doses of niacin are used to manage dyslipidaemia by lowering LDL cholesterol and raising HDL cholesterol, though they may cause flushing as a common side effect.