What Is Niacin Flush?


Niacin is a vitamin, dietary supplement and prescription drug, depending on the amount taken and purpose for which it is taken. Dosing as a prescription drug starts at 500 mg per day and is increased over time to as high as 3,000 mg per day. Niacin lowers blood triglycerides and cholesterol. Niacin “flush” refers to the most prominent side effect: a reddening of the face and neck within 15 to 30 minutes after taking niacin. The flush effect can be avoided.

Niacin as Vitamin

The Estimated Average Requirement for niacin as an essential vitamin is 12 mg per day, an amount too low to trigger flush or other side effects. Most daily multivitamin/mineral products contain this much niacin. Most U.S. adults consume more than this intake from diet alone.

Niacin as Drug

Prescription niacin is sold in an immediate-release form as Niacor, or in the extended-release form as Niaspan. Niacor dosing starts at 500 mg per day and may be increased to as high as 3,000 mg per day if the desired blood lipid concentrations are not reached with the lower doses. Niaspan doses range 500 to 2,000 mg per day. Flushing occurs less often and with less intensity with extended-release Niaspan. Both products lower triglycerides and low-density lipoprotein cholesterol, and have the added benefit of raising high-density lipoprotein cholesterol–the “good” cholesterol. Niacin can be combined with statin drugs prescribed to lower low-density lipoprotein cholesterol.

The “Flush”

Flushing of the face and neck, i.e., a visible reddening, is a common side effect. It may be accompanied by a feeling of warmth, sweating, chills, tingling, burning sensation and itching. This side effect is worst when someone first starts taking niacin, which is why standard treatment starts at a low dose increased over subsequent weeks. Niacin causes these symptoms by triggering a release of inflammatory compounds called prostaglandins.

Minimizing Flush

In the September 2009 issue of the International Journal of Clinical Practice Dr. V. S. Kamanna reviewed the causes and preventive treatments for niacin flush. Pretreating with a prostaglandin synthesis inhibitor such as aspirin will reduce the flush response, as will co-treating with laropiprant, a prescription prostaglandin receptor blocker. Neither of these co-treatments impair the desired lipid changes.

Other Side Effects

The most common side effects from taking niacin other than flush are diarrhea, vomiting, itching, dizziness and increased cough. Less common but more severe side effects include racing heartbeat, gastrointestinal bleeding, liver damage, elevated blood sugar among others.

Why Not Take a Supplement?

The American Heart Association advises against nonprescription niacin supplements for managing cholesterol and triglycerides. People buying over-the-counter products might not be aware of possible adverse effects or drug interactions. Anyone with a history of liver disease or gout, alcohol consumption or use of a blood thinner must be closely supervised by a physician while using niacin, as do patients co-using a prescription statin drug for cholesterol control.

About this Author

David A. Mark is a nutrition science consultant to the sports nutrition, functional food and dietary supplement industries. Mark has been writing for health and trade publications since 2004. He earned his doctorate in nutritional biochemistry from the Massachusetts Institute of Technology in 1981.