← The FormularyLong gameNiacin
Also known as Vitamin B3 / nicotinic acid / nicotinamideThe flush is famous. The dose is the point.
Niacin is the clearest example of a nutrient that becomes a different thing at a different dose. At 16 mg it is a vitamin. At one to three grams it was, for decades, a cholesterol drug — and at that dose it causes an intense skin flush, and it can injure the liver, with the sustained-release formulations being the worst offenders. The upper limit for supplemental nicotinic acid is 35 mg for exactly this reason. Our products carry about a third of a day's requirement inside a B-complex, which is a nutrient amount and nowhere near any of that. If you see a product offering 500 mg, you are looking at pharmacology, not nutrition.
A water-soluble B vitamin that comes in two forms with different behaviour: nicotinic acid, which flushes, and nicotinamide, which does not.
Nearly every reaction that releases energy from food hands electrons to NAD. That makes niacin one of the most heavily used vitamins in the body — and it is also why the body can make some of its own from tryptophan, an amino acid, which is unusual for a vitamin and a decent safety margin.
Becomes NAD and NADP, the electron carriers that run energy metabolism in every cell, and supports normal skin and nervous-system function.
Everyone needs it and almost everyone gets it. Supplemental niacin at nutritional amounts belongs in a complex; anything more belongs in a prescription.
Daily inside the complex, with food. If a niacin product makes you flush, that is nicotinic acid at a pharmacological dose, and worth questioning.
Nothing at nutritional amounts — no flush, no sensation.
Grade A as an essential nutrient. The tolerable upper limit of 35 mg/day for supplemental nicotinic acid is set by the flushing threshold. Hepatotoxicity is dose-dependent and notably more common with sustained-release preparations; gram-level niacin was historically used as a lipid-lowering drug under supervision.
Read the labelHigh-dose niacin causes flushing, and can damage the liver — particularly sustained-release forms. Do not take gram-level niacin except under medical supervision. Speak to a doctor first if you have liver disease, gout or diabetes.
Evidence grades describe how well an ingredient is studied — A well-supported, C emerging — not a promise of results. Educational, not medical advice. Doses are typical ranges; follow the label on the product.