Vitamin B3 (Niacin)

Alternative names

Diet – niacin; Nicotinic acid


Niacin is a water-soluble vitamin necessary for many aspects of health, growth, and reproduction. It is part of the vitamin B complex.


Niacin assists in the functioning of the digestive system, skin, and nerves. It is also important for the conversion of food to energy.

Food Sources

Niacin (also known as vitamin B3) is found in dairy products, poultry, fish, lean meats, nuts, and eggs. Legumes and enriched breads and cereals also supply some niacin.

Side Effects

A deficiency of niacin causes pellagra. The symptoms include inflamed skin, digestive problems, and mental impairment.

Large doses of niacin can cause liver damage, peptic ulcers, and skin rashes. Even normal doses can be associated with skin flushing. It can be prescribed as a treatment for elevated total cholesterol and other types of lipid disorders, but it should only be used with medical supervision due to its potential for severe side effects.

Although the Daily Value for niacin is only 20mg and the body can convert tryptophan (an amino acid) into niacin, a “cholesterol-lowering” dose of niacin (as nicotinic acid, NOT niacinamide or nicotinamide) is typically in the range of 250-2000mg/day. Dosing is usually started at the low-end (250mg/day) with increasing doses of 250mg each week or two until blood lipid levels start to normalize (or side effects develop). Side effects are usually minimized by increasing the dosage slowly to the common therapeutic range of 1000-2000mg/day (and should be divided into 2-3 separate doses or no more than 500-750mg per one dose). In some cases, the skin flushing and itching side effects can be reduced somewhat by combined use with an aspirin (which also has a beneficial cardiovascular effect via reduced blood clotting).

All niacin therapy (at doses exceeding 100mg/day) should be supervised and monitored by a physician.