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Niacin Excess

(Niacin Toxicity; Nicotinic Acid Toxicity)


Larry E. Johnson

, MD, PhD, University of Arkansas for Medical Sciences

Last full review/revision Nov 2020| Content last modified Nov 2020
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Niacin (nicotinic acid but not nicotinamide) in high doses may be prescribed to improve cholesterol and triglyceride (lipid) levels in the blood.

Niacin, a B vitamin Overview of Vitamins Vitamins are a vital part of a healthy diet. The recommended dietary allowance (RDA)—the amount most healthy people need each day to remain healthy—has been determined for most vitamins. A safe... read more , is essential for the processing (metabolism) of carbohydrates, fats, and many other substances in the body and for the normal functioning of cells. Good sources of niacin include dried yeast, liver, red meat, poultry, fish, legumes, and whole-grain or enriched cereal products and bread.

The term "niacin" is used in two ways: as a synonym for nicotinic acid and as a broader term that includes nicotinamide and nicotinic acid, two forms of this B vitamin.

High doses of nicotinic acid can have the following beneficial effects:

  • Decrease triglyceride levels

  • Increase high-density lipoprotein (HDL—the good) cholesterol levels

  • Moderately decrease low-density lipoprotein (LDL—the bad) cholesterol levels

Such high doses of nicotinic acid can cause flushing, itching, gout Gout Gout is a disorder in which deposits of uric acid crystals accumulate in the joints because of high blood levels of uric acid (hyperuricemia). The accumulations of crystals cause flare-ups ... read more Gout , and liver damage (rarely) and increase the level of sugar (glucose) in the blood. Flushing may be worse after drinking alcohol, being physically active, being in the sun, and eating spicy foods.

Most side effects can be minimized by starting with a relatively low dose and gradually increasing the dose. Taking aspirin before taking nicotinic acid and taking nicotinic acid after meals also help.

If the side effects of nicotinic acid are intolerable, the dose may be decreased, other (especially extended-release) formulations may be tried, or nicotinic acid may be stopped and another lipid-lowering drug Lipid-Lowering Drugs Dyslipidemia is a high level of lipids (cholesterol, triglycerides, or both) or a low high-density lipoprotein (HDL) cholesterol level. Lifestyle, genetics, disorders (such as low thyroid hormone... read more Lipid-Lowering Drugs substituted.

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