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.

A niacin flush starts about 30 minutes after you take a large dose (like around 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 have a niacin flush with these symptoms, you should call your doctor for advice.

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

There are a couple of things you can do to avoid or lessen the niacin flush. Taking a regular aspirin about 30 minutes before taking the niacin supplements helps reduce the discomfort but probably won't eliminate it altogether. Another option is to use time-release forms of niacin, which is absorbed and metabolized slower than regular niacin.

There's also a supplement called inositol hexanicotinate, which your body converts to niacin and 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 review study published in Nutrition Reviews in 2012 reports that inositol hexanicotinate was no better than a placebo for lowering cholesterol levels.

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 your body needs for all your daily activities. It's also needed for your digestive system to function properly and for normal skin and nerve function. The average adult needs about 14 milligrams per day.

The vast majority of people don't need to take niacin supplements because there's plenty of niacin the foods found in a typical diet, even diets that aren't all that healthy. For example, 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.

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

Be careful, though, if you're thinking about taking niacin for your high cholesterol levels. Even though the niacin flush is harmless, you shouldn't mess around with niacin supplements without talking to your healthcare provider. Large doses of niacin can interact with many different medications, and long-term use can cause liver damage, skin rashes, gastrointestinal problems, and elevated blood sugar.