Niacin flush is a side effect of taking too much niacin or vitamin B3. Symptoms may include blushing on your face and upper body, and itchiness or burning sensations.
Medically reviewed by Jennie Olopaade, PharmD, RPH
Medically reviewed by Jennie Olopaade, PharmD, RPH on May 4, 2023
Niacin is a type of vitamin B that’s soluble in water. Also known as vitamin B3, niacin contributes to your skin and nervous system health and helps your body turn food into energy.
Niacin also affects cholesterol levels. It can increase the “good cholesterol,” or high-density lipoprotein (HDL), and decrease triglycerides.
Niacin flush is a side effect of taking high doses of niacin prescriptions or supplements.
This article will discuss why niacin flush happens, its symptoms, and what you can do to prevent it.
What is a niacin flush?
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Niacin flush is an adverse effect of taking high doses of niacin. It happens when small blood vessels known as capillaries expand and increase blood flow to your skin.
Your skin changes color, depending on your skin tone, from the blood rushing to the surface. This sudden rush of blood also causes itchiness.
Although uncomfortable, niacin flush is not dangerous to your health or a medical emergency.
What is niacin for?
Niacin is an essential vitamin necessary for overall health. Typically, you can get enough of it from foods like red meat, fish, legumes, and bananas.
Niacin comes as a prescription medication, like Niacor (Niaspan), or over-the-counter (OTC) supplements.
Your healthcare team may recommend these forms of niacin if they detect a nutrient deficiency, or as an aid to manage cholesterol levels or chronic pain.
Therapeutic doses of prescription niacin may vary depending on many factors, including overall health, medical goals, and other medications you may be taking.
A niacin rush typically results from taking 500 mg or more of niacin or 30 mg or more of nicotinic acid (a chemical form of niacin).
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Niacin flush is less likely to occur when you take slow-release niacin.
Niacin has two main chemical forms: nicotinic acid and niacinamide (or nicotinamide).
Niacin supplements usually come in the form of nicotinic acid and can be:
Immediate-release capsules or tablets: In this form, the body absorbs the entire niacin dose at once.
Extended or slow-release capsules or tablets: In this form, the nicotinic acid slowly dissolves into your body over a few hours.
How long does a niacin flush last?
Symptoms of a niacin flush may last for about 1 to 2.5 hours. In some people, flushing lasts for a couple of days or even weeks.
You may feel uncomfortable during a niacin flush, but the side effect is not dangerous or harmful to your health.
If your symptoms do not subside or they are affecting your quality of life, consider discussing them with a healthcare professional. They may recommend a different niacin supplement or an alternative way of managing cholesterol or pain.
changes in the color of your skin, usually in your face, arms, and chest, similar to when you blush
skin itching
overall tingling in your face or upper body
burning sensation in your face or upper body
skin that is warmer to the touch compared to other areas
Symptoms of niacin flush may appear within 30 minutes of taking a niacin supplement.
Rare symptoms of a niacin flush
Niacin flush may also lead to symptoms like:
headaches
dizziness o lightheadedness
rashes
nausea and vomiting
loss of appetite
fatigue
depression
These symptoms may be more likely to occur if you take niacin on an empty stomach or if you take it with hot drinks or alcohol.
In some cases, long-term higher doses of niacin — 2,000 to 3,000 mg a day — may cause severe side effects like:
low blood pressure (hypotension)
liver damage
insulin resistance
heartburn
blurred vision
Because of many of the symptoms associated with niacin intake, some medical professionals have moved away from using it as a therapeutic aid.
Who should avoid niacin?
Your healthcare team may not recommend high doses of niacin if you live with:
liver disease
low blood pressure
kidney disease
peptic ulcer disease
gout
diabetes
You may also want to avoid niacin prescriptions if you’re pregnant or nursing.
Niacin may also interact with other cholesterol-lowering medications, anticoagulants, and diabetes drugs. Let all medical professionals know if you are taking niacin.
How to prevent a niacin flush?
To prevent niacin flush, consider:
taking niacin with meals
limiting or avoiding alcohol consumption, if applicable
Niacin, or vitamin B3, helps your body turn food into energy and keep your skin and nervous system healthy.
With a balanced diet, you can have an adequate intake of niacin. But niacin supplements and prescriptions may help with managing cholesterol levels and easing arthritis symptoms.
One of the side effects of taking high doses of niacin is flushing, which occurs when the skin on your face and upper body blushes, itches, or burns.
Niacin flushing is not dangerous or harmful and typically goes away within hours.
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