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How Long Does a Niacin Flush Last, and Is It Harmful?

A telltale sign of niacin overdose is flushing (redness) of the skin.

A telltale sign of niacin overdose is flushing (redness) of the skin.

Niacin (vitamin B3) is necessary for a variety of functions in the body, but it is most often prescribed to help patients reduce their cholesterol levels. You can also find niacin as an over-the-counter supplement at most grocery and health stores and in foods such as brown rice, avocado, chicken breast, tuna, and turkey.

Despite its importance in the body, taking too much of it can cause unwanted side effects, the first and most noticeable one being redness and tingling of the skin, otherwise known as a niacin flush.

Below, I'll share the embarrassing story of my first niacin flush and the subsequent attempts to avoid experiencing another one.

I had been reading about all the B vitamins the night before, so the following day, while I worked (I work in a supermarket), I was thinking about all the benefits they offer, and I couldn’t wait to buy some. When it came time for my break, I bought a B complex and extra thiamine (B1) and niacin (B3). I took one of each and went back to work. Let good health begin!

What Does a Niacin Flush Feel Like?

But something else began first. Ten minutes after taking the B supplements, I felt pins and needles in my face. Then, I felt really warm. I went to the bathroom to look in the mirror. My face and neck were red, and a minute later, my arms were totally red too. I was warm and tingling all over, and my face felt slightly stiff.

I didn’t want any customers to see me as I looked like I had a bad sunburn. I tried to stay out of my supervisor’s sight, but he eventually saw me. He enquired about my health, physical and emotional, as the nature of my suffering was unclear. To cool myself down, I knew I had to go stand in the freezer, so I came up with some work I could do in there.

Niacin Function and Side Effect

Niacin is a vasodilator. It opens up the blood vessels to increase blood flow throughout the body—including the capillaries under the skin to result in the unsightly niacin flush. This is usually accompanied by a warm feeling on the skin with possible tingling and itching.

How Long Does a Niacin Flush Last?

The worst of the reaction lasted about an hour and a half. The all-over redness and warmth lasted the entire time. There was intermittent tingling and itching on my legs as well. I didn’t realize the reaction would be so intense and would make me look so ridiculous. Based on what I've read, it seems that the flush can last between 20 minutes and two hours, depending on the size of the dose and if it’s taken alone or with food.

I had read about niacin flushes, so I knew what was happening. If I hadn’t been aware of the side effect, I would have thought there was something seriously wrong (maybe the vitamins were poisoned or I was allergic?), and I might have gone to the hospital. Having read that niacin flushes were harmless, I waited it out.

How Much Niacin Does It Take to Induce Flushing?

The daily recommended dose is around 15 mg of niacin, while doses above 1500mg are prescribed to treat high cholesterol. From what I've read, 50 mg is enough to cause flushing in some people, although this might depend on the individual and how they take it. I took 500 mg of niacin on an empty stomach, which is probably why my reaction started so quickly and lasted so long.

Can You Avoid a Niacin Flush?

To avoid another horrible flush, I cut up my niacin tablets into fours so I could take about 125 mg at a time. I took one of them the next morning with food and didn’t experience any flushing. I continued taking 125 mg a few more times with no reaction.

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Two days later, I bumped it up to two 125 mg doses (250 mg total). Again, no reaction.

On the third night, before bed, I went to 375 mg with food. I didn’t feel anything before falling asleep. I thought I was in the clear. However, I had a dream that I was flushing and trying to find a way to cool down.

I woke up to a niacin flush. It was three hours later. I felt this one in my dream for what felt like 10 minutes and continued to feel it after I woke up for about 20 minutes. I’m guessing this one lasted about a half hour, but I don’t know how long had been happening while I was asleep. Luckily, the intensity was nowhere near like it was the first time.

On the fourth night, I dropped down to 250 mg to avoid flushing, but, to my surprise, I experienced a flush about a half hour after taking it. The explanation seems to be this: My earlier doses of 250 mg were taken as two pieces of 125 mg taken separately with my food. This most recent dose was a single piece of 250 mg. The 375 mg dose on the third night was also one piece.

Breaking the niacin up the dose and spacing them by about a minute seems to have been enough to avoid the flush. I’m going to experiment further with how many smaller pieces I can take without flushing.

What I've Learned

Experiencing my first niacin flush was interesting, and I’m glad I did. I just wish it hadn’t lasted so long and that I had been home at the time. If you plan on taking niacin as a supplement or as a prescribed treatment for high cholesterol, talk to your doctor about the possible side effects first. You may have to start with small doses to see how you react.

Another tip is to take it at home, especially your first time. This saves you the embarrassment of being red all over, and you can just jump in a cool bath if necessary.

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2015 Howard Allen


Howard Allen (author) on August 22, 2017:


There are lots of different bottles and brands available at supplement stores and grocery stores, and also online. I don't recommend any specific brand.

Shieh on August 22, 2017:

How does the bottle look for these supplements and where can i find them???

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