Niacin (Vitamin B3): Dose Limits, Flushing and What the NIH Says
What niacin does
Niacin, also called vitamin B3, helps cells convert food into energy and is a building block of NAD+, a coenzyme involved in hundreds of reactions. The NIH Office of Dietary Supplements fact sheet on niacin covers foods, needs and safety.
Food versus supplement
Most adults get enough niacin from meat, fish, poultry, grains and fortified cereals. Deficiency is rare in developed countries. Supplemental niacin is sold in several forms, and the effects differ by form and dose.
The flushing effect
The nicotinic acid form of niacin can dilate small blood vessels in the skin, causing warmth, redness and tingling that typically fades within an hour. It is harmless for most people but can be alarming. Taking it with food and avoiding hot drinks at the same time may lessen it, but ask your clinician.
Upper limits and cautions
The NIH sets a tolerable upper intake level for adults for niacin from supplements and fortified foods, mainly to avoid flushing and, at higher doses, liver effects. We do not quote the exact figure here because it can be revised, so check the current fact sheet. People with liver disease, ulcers, gout or diabetes, and anyone on statins or blood-pressure medicines, should ask a clinician before taking supplemental niacin.
Niacin and memory
A large study followed dietary niacin and the risk of Alzheimer's disease and cognitive decline, which links food intake, not supplements, with outcomes. It cannot show that a capsule improves memory.
Reading a label
HoneyPezil lists niacin but its order page does not give the amount, so check your bottle's Supplement Facts panel against the NIH limit. Our label guide explains the panel.
Forms of niacin on labels
Labels may list niacin as nicotinic acid, nicotinamide (niacinamide) or inositol hexanicotinate, sometimes called "no-flush" niacin. They differ in how they affect the skin and in what they are used for, so always read the form. Your clinician can advise which, if any, is appropriate for you.
When to get advice
Ask a clinician before using niacin supplements if you have liver disease, gout, ulcers, diabetes or take cholesterol or blood-pressure medicines.
Frequently asked questions
Sources
- NIH Office of Dietary Supplements: Niacin fact sheet
- PubMed: Dietary niacin and the risk of incident Alzheimer's disease and of cognitive decline (2004)
General information, not medical advice. Offer details were checked on November 11, 2026; confirm on the order page and read the label on your bottle. See our disclaimer and how we research.