Niacin toxicity presents mainly with which symptom?

• A. Nausea
• B. Flushing
• C. Hair loss
• D. Dizziness

Answer: (B)

Niacin toxicity is classically marked by cutaneous flushing. This occurs because high-dose niacin triggers prostaglandin release that dilates small skin vessels, causing a warm, red, sometimes itchy face and upper body within minutes to an hour after taking the dose. It’s the symptom most people associate with niacin toxicity, especially at the doses used to treat high cholesterol. Strategies to lessen flushing include taking it with food, using slower-release formulations, or taking an aspirin before the dose to inhibit prostaglandin production.

Other symptoms like nausea, hair loss, or dizziness can occur, but they are not the hallmark features of niacin toxicity and are less specific. Long-term, high-dose use can also raise blood glucose and uric acid or risk hepatotoxicity, but the immediate, characteristic sign is flushing.