Orally, niacin is used for hyperlipidemia. It is also used in conjunction with other therapies for peripheral vascular disease, vascular spasm, migraine headache, Meniere's syndrome, vertigo, and to reduce the diarrhea associated with cholera. Orally, niacin or niacinamide is also used for preventing vitamin B3 deficiency, treating pellagra, schizophrenia, drug-induced hallucinations, Alzheimer's disease and age-related cognitive decline, chronic brain syndrome, hyperkinesis, depression, motion sickness, alcohol dependence, vasculitis associated with skin lesions, and edema. Niacin or niacinamide is also used for acne, leprosy, attention deficit-hyperactivity disorder (ADHD), preventing premenstrual headache, improving digestion, for protection from toxins and pollutants, for reducing the effects of aging, memory loss, arthritis, lowering blood pressure, improving circulation, promoting relaxation, improving orgasm, and preventing cataracts. Niaicn is also used for preventing positive urine drug screens in people who take illicit drugs. Niacinamide is also used orally treating diabetes, and the skin conditions bullous pemphigoid and granuloma annulare.

Topically, niacinamide is used for treating inflammatory acne vulgaris.

via NIACIN AND NIACINAMIDE (VITAMIN B3) Monograph: Natural Medicines Comprehensive Database.