What are the Signs of a Niacin Overdose?

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  • Written By: Malcolm Tatum
  • Edited By: Bronwyn Harris
  • Last Modified Date: 14 October 2019
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While it is very difficult to ingest too much vitamin B3 or niacin, it is possible to experience a niacin overdose from taking an overabundance of vitamin supplements. Thanks to the fact that vitamin B3 is water-soluble and very little is stored in the body at any one time, the chances of overdosing are relatively low. Unfortunately, when too much niacin is consumed, serious side effects such as dizziness, skin flushing, nausea, and pain in the abdomen may occur. Prolonged overdosing on the nutrient can even lead to hepatoxicity, or permanent damage to the liver.

While skin flushing is relatively common when niacin as nicotinic acid is consumed, the flushing is normally short-lived, but some slight tingling may also occur. This is due to the dilating effect the supplement has on the veins within the body. When an inordinate amount of niacin is consumed, the flushing may be extremely intense, and can be accompanied by dizziness as well as prolonged periods of tingling that turn into itching. Some people have reported that attempting to consume more than one gram of niacin at a time also causes numbness of the lips as well as dizziness and a prolonged period of flushing.


Rapid heartbeat is another common sign of niacin overdose. The change in heart rate may occur along with other symptoms or emerge as the only apparent symptom of the overdose. Of all the outward manifestations of a niacin overdose, this is the one that often causes the highest degree of alarm. Should the increased palpitations continue for more than a short period of time, medical attention should be obtained as quickly as possible.

Pain in the abdominal area may also occur from a niacin overdose, especially if the supplement is taken on an empty stomach. Physicians who prescribe larger doses of niacin as treatment for cholesterol issues sometimes recommend that patients take the niacin during or after a meal, rather than between meals, in order to avoid the potential for cramping and discomfort in the area of the stomach. In some cases, the cramping is accompanied by diarrhea. Fortunately, consuming some type of soft food will often help to calm the stomach pain and counteract the niacin overdose to some degree.

While many of the signs of a niacin overdose are quickly resolved, there is one potential side effect that has a lasting impact. Continued usage of exceptionally high dosages of niacin may result in damage to the liver, known as hepatoxicity. This condition can be treated, but is considered irreversible. While there is no consensus on what constitutes a risk level of niacin consumption, many physicians do not recommend more than three grams per day. In any event, niacin supplements of more than the amounts typically found in multi-vitamins should not be taken without consulting a physician, and that dosage should never exceed the amount determined by the doctor to be safe for the individual patient.


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Post 3

@fify-- Well, if someone has all three of those symptoms, it probably is an overdose, even if it's a mild one. It's not normal to experience such intense flushing that kind of feels like the skin is burning. That's what happened to me when I took way too much niacin trying to reduce my cholesterol.

The other side effect of too much niacin is very low blood pressure. That's actually where the dizziness and confusion comes from. Niacin can reduce blood pressure because it improves circulation and dilates blood vessels. For someone with normal blood pressure or blood pressure on the lower end, it can be very problematic.

If possible, people should get niacin from food rather than supplements. There are many foods rich in niacin and natural sources never cause an overdose. Moreover, I think the body absorbs niacin in food better and more easily.

Post 2

I think it can be rather difficult to tell a niacin overdose from flushing because it's so common a side effect. The article described a more intense flushing accompanied by itching and tingling with an overdose. But I know people who experience these whenever they use a niacin supplement.

Post 1

I don't believe that overdosing on niacin is as difficult as people think. Although this vitamin is water soluble and the excess gets thrown out of the body, it takes time for this to happen. Meanwhile, the niacin is still in the system and high doses or frequent doses can definitely cause an overdose.

We also know that niacin supplements are often used by people with high cholesterol and they take very high doses for it to be effective. Since everyone's kidneys and liver function at varying rates, a dose that's safe for one person may actually cause an overdose in another. It's always best to never take more than the recommended amount. In fact, it's my rule to always take the lowest effective dose of any supplement. I also take a break from such supplements every couple of weeks to avoid overdoses.

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