Is a Niacin Flush Dangerous for You?

A niacin flush is a side effect of taking large doses of niacin (vitamin B3) supplements. The flush happens when the niacin causes the small blood vessels in your skin to dilate so more blood can rush through. Almost everyone who takes large doses of niacin experiences this flush. It isn't harmful, but it can scare you if you don't know it's coming.

While no one needs large doses of niacin, some people take it as a supplement to reduce the risk of heart disease and atherosclerosis. Large daily doses of niacin may help to lower LDL cholesterol (the bad cholesterol) and increase HDL cholesterol (the good form of cholesterol).

Symptoms of Niacin Flushing

A niacin flush starts about 30 minutes after you take a large dose (30 to 50 milligrams or more). The flush includes reddening of the skin accompanied by a burning or itching sensation. Flushing of the face is the most common, but it can also occur in the neck and upper body. The flush gets better over time and is usually gone within an hour or two.

The niacin flush is generally harmless, but may occasionally be accompanied by a headache, dizziness, or drop in blood pressure. If you experience these symptoms with a niacin flush, you should call your doctor for advice.

Prevention

You won't get the niacin flush reaction after taking multiple vitamins that contain smaller amounts of niacin. It only happens when you take massive doses. The average adult needs about 14 milligrams per day, so megadoses of individual niacin supplements are far more than anyone needs.

To avoid or lessen the niacin flush, you could use time-release forms of niacin, which are absorbed and metabolized slower than regular niacin. Taking a regular aspirin about 30 minutes before taking niacin supplements may also help reduce the discomfort, but probably won't eliminate it altogether.

Another alternative is inositol hexanicotinate, which your body converts to niacin. The conversion is slow enough that it doesn't cause a flush in most people. The problem is that you may not get the same lipid-lowering benefit as regular niacin. A 2012 review study reported that inositol hexanicotinate was no better than a placebo for lowering cholesterol levels.

Niacin Requirements

Along with thiamin, riboflavin, and others, niacin is an essential B-complex vitamin your body needs to convert macronutrients from the food you eat into energy for daily activities. It also helps your digestive system function properly and supports normal skin and nerve function.

The vast majority of people don't need to take niacin supplements because there's plenty of niacin in the foods found in a typical diet, even diets that aren't all that healthy. Nuts, legumes, eggs, poultry, beef, and seafood are all high in niacin, and it's found in smaller amounts in most other foods. So as long as you're eating every day, you're getting plenty of niacin.

A Word From Verywell

Be careful if you're thinking about taking niacin for your high cholesterol levels. Even though the niacin flush is harmless, large doses of niacin can interact with many different medications. Long-term use can cause liver damage, skin rashes, gastrointestinal problems, and elevated blood sugar. Discuss niacin supplements with your healthcare provider before taking them.