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Niacin flush side effects: Is Niacin Flush Harmful?

Is Niacin Flush Harmful?

Niacin flush is a common side effect of taking high doses of supplemental niacin, which treats cholesterol problems. While harmless, its symptoms — skin that’s red, warm, and itchy — can be uncomfortable.

The symptoms of niacin flush can make people stop taking niacin (1). The good news is that you can reduce your likelihood of getting niacin flush.

This article describes what you need to know about niacin flush, including:

  • what it is
  • what causes it
  • what you can do about it

Niacin flush is a common side effect of taking high doses of niacin supplements. It’s uncomfortable, but it’s harmless.

It appears as a flush of red on the skin, which may be accompanied by an itching or burning sensation (1).

Niacin is also known as vitamin B3. It’s part of the B complex of vitamins that play an essential role in turning food into energy for the body (2).

As a supplement, niacin is primarily used to treat high cholesterol levels. Nicotinic acid is the supplement form people usually use for this purpose.

The other supplemental form, niacinamide, doesn’t produce flushing. However, this form isn’t effective at altering blood fats, such as cholesterol (3).

There are two main forms of nicotinic acid supplements:

  • immediate release, where the whole dose is absorbed at once
  • extended release, which has a special coating that makes it dissolve more slowly

Niacin flush is a very common side effect of taking the immediate-release form of nicotinic acid. It’s so common that at least half of people who take high doses of immediate-release niacin supplements experience it (4, 5).

High doses of nicotinic acid trigger a response that causes your capillaries to expand, which increases the flow of blood to the skin’s surface (1, 6, 7, 8).

By some reports, virtually every person who takes high doses of nicotinic acid experiences flush (6).

Other medications, including some antidepressants and hormone replacement therapies (HRTs), can also trigger flush (1).


Niacin flush is a common reaction to high doses of niacin. It happens when capillaries expand, increasing blood flow to the skin’s surface.

When niacin flush occurs, symptoms typically set in about 15–30 minutes after taking the supplement and taper off after about an hour.

The symptoms mainly affect the face and upper body, and include (9, 10):

  • Reddening of the skin. It can appear as a mild flush or be red like a sunburn.
  • Tingling, burning, or itching. This can feel uncomfortable or even painful (9).
  • Skin that’s warm to the touch. As is the case with sunburn, skin may feel warm or hot to the touch (11).

People generally develop a tolerance to high-dose niacin. So even if you experience niacin flush when you first start taking it, that will probably stop in time (1, 8).


Niacin flush can appear and feel much like a sunburn. However, symptoms typically go away after an hour. People usually develop a tolerance to the supplements over time.

Doctors have long prescribed high doses of niacin to help people improve their cholesterol levels and prevent heart disease (5).

Taking high doses of niacin has been shown to produce the following improvements in blood cholesterol and lipids:

  • Increase HDL (good) cholesterol. It prevents the breakdown of apolipoprotein A1, which is used to make HDL (good) cholesterol. It can increase HDL (good) cholesterol by up to 20–40% (1, 12).
  • Reduce LDL (bad) cholesterol. Niacin speeds the breakdown of apolipoprotein B in LDL (bad) cholesterol, causing less to be released by the liver. It can reduce LDL (bad) cholesterol by 5–20% (11, 13, 14).
  • Lower triglycerides. Niacin interferes with an enzyme that’s essential for making triglycerides. It can lower triglycerides in the blood by 20–50% (3, 11).

People only experience these positive effects on blood fats when they take therapeutic doses of niacin in the range of 1,000–2,000 mg per day (5).

To put that in perspective, the recommended daily intake for most men and women is 14–16 mg per day (9, 10).

Niacin treatment isn’t typically the first line of defense against cholesterol problems, since it can cause side effects other than flush.

However, it’s often prescribed for people whose cholesterol levels don’t respond to statins, which are the preferred treatment (15).

It’s also sometimes prescribed to accompany statin therapy (16, 17, 18, 19).

Niacin supplements should be treated like a drug and only taken under medical supervision, since they can have side effects.


High doses of niacin are typically used to improve cholesterol and triglyceride counts. They should only be taken under medical supervision, since they carry a risk of side effects.

Niacin flush is harmless.

However, high doses of niacin can cause other, more dangerous side effects, although these are rare (20).

The most harmful of these is liver damage. High doses of niacin may also cause stomach cramping, so don’t take them if you have a stomach ulcer or active bleeding (9, 21, 22, 23, 24).

You also shouldn’t take high doses if you’re pregnant since it’s considered a category C drug, meaning at high doses, it could cause birth defects (22).

Interestingly, although the flush isn’t harmful, people often cite it as the reason they want to discontinue their treatment (1).

And that in itself can be a problem, since if you don’t take niacin as it’s prescribed, it’s not at all effective at preventing heart disease.

According to reports, 5–20% of people who have been prescribed niacin stop using it because of flush (5).

If you’re experiencing niacin flush, or are concerned about it as a possible side effect of these supplements, tell your healthcare provider. They can help you figure out how to reduce the chances of flush or discuss alternative treatments.

Also, because there are other, more harmful side effects associated with taking these supplements, do not try self-medicating with niacin.


Niacin flush is harmless. However, the supplements can have other harmful side effects, and certain people should not take them.

Here are the main strategies people use to prevent niacin flush:

  • Try a different formula. Roughly 50% of people taking immediate-release niacin experience flushing, but extended-release niacin is less likely to cause it. And even when it does, symptoms are less severe and don’t last as long (1, 4, 11). However, extended-release forms may carry a greater risk of liver damage.
  • Take aspirin. Taking 325 mg of aspirin 30 minutes before the niacin can help reduce the risk of flush. Antihistamines and nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, can also minimize the risk (5, 10, 25, 26).
  • Ease into it. Some experts recommend starting with a smaller dose like 500 mg and then increasing to 1,000 mg gradually over the course of 2 months, before finally increasing to 2,000 mg. This strategy could bypass flush entirely (5).
  • Have a snack. Try taking niacin with meals or with a low-fat evening snack (5).
  • Eat an apple. Some early research suggests that eating an apple or applesauce prior to taking niacin may have a similar effect to aspirin. Pectin in apple seems to be responsible for the protective effect (10).


Taking aspirin, eating a snack, slowly increasing the dosage, or switching formulas may help you prevent niacin flush.

As mentioned above, to avoid unwanted symptoms, including flushing, some people opt for extended-release or long-acting niacin.

However, extended-release and long-acting niacin differ from immediate-release niacin and may cause different health effects.

Long-acting niacin is associated with significantly reduced flushing, as it’s absorbed over a long time period that typically exceeds 12 hours. Because of this, taking long-acting niacin significantly reduced the chances of flushing (11).

However, because of the way the body breaks it down, taking long-acting niacin may have toxic effects on the liver, dependent on the dose taken (11).

Although uncommon, switching from an immediate-release niacin to a long-acting niacin or significantly increasing your dose can result in serious liver damage (27).

What’s more, niacin absorbability depends on the niacin supplement that you take.

For example, the body absorbs nearly 100% of nicotinic acid, which raises niacin blood levels to an optimal range in about 30 minutes.

In contrast, inositol hexanicotinate (IHN), a “no-flush” niacin, isn’t absorbed as well as nicotinic aid (28).

Its absorption rate varies widely, with an average of 70% being absorbed into the bloodstream.

Plus, IHN is significantly less effective than nicotinic acid at increasing serum niacin. IHN usually takes between 6-12 hours to raise blood levels of niacin to near the optimal range (28).

Some studies suggest that peak niacin blood levels can be over 100 times greater when supplementing with nicotinic acid compared to supplementing with IHN.

Research also shows that IHN has minimal effect on blood lipid levels (28).

Because absorbability can significantly vary depending on the form of niacin used, it’s a good idea to ask your healthcare provider what form would be best for your specific health needs.


Absorbability differs between forms of niacin. Some types of niacin are more effective at raising blood levels than others.

Niacin flush can be an alarming and uncomfortable experience.

However, it’s actually a harmless side effect of high-dose niacin therapy. What’s more, it may be preventable.

That said, large doses of niacin can have other, more harmful side effects.

If you want to take high doses of niacin for health reasons, make sure to do so under medical supervision.

Why does it occur? Is it dangerous?

Niacin flush is a flushing of the skin that can occur after taking higher doses of niacin (vitamin B3) as supplements or prescription medications. A harmless and temporary side effect, it usually goes away without treatment in 1–2 hours.

People may also call niacin vitamin B3. Niacin may come in the form of nicotinic acid or nicotinamide.

In this article, we examine niacin flush and its associated symptoms. We also discuss why people may use niacin, whether it is harmful, and how to prevent niacin flush.

High doses of niacin can cause the skin to flush, and people may experience an itching or hot, prickly sensation on the skin. Although it may seem like an allergic reaction, it is not. Flushing may affect the face and upper body.

Flushing occurs from dilating blood vessels, which increases blood flow and causes the skin to redden or darken. The dilation of blood vessels may occur due to how niacin reacts with certain proteins within the skin, causing an increase in prostaglandins and the blood vessels to dilate.

Many people taking niacin may experience a niacin flush. People may experience flushing around 30 minutes after taking a high dose of niacin, such as 500 milligrams (mg) or above.

Symptoms of niacin flush may include:

  • the skin on the face and upper body flushing
  • itching, tingling, or prickly sensations on the skin
  • a hot or burning sensation on the skin

Symptoms of niacin flush may clear within 1–2 hours of taking niacin.

People may find that symptoms of niacin flush are most intense when they first start taking high doses of niacin but may reduce with continued use.

The National Institutes of Health (NIH) recommends a daily niacin intake of 14 (milligrams) mg for adult females and 16 mg for adult males.

People may take high doses of niacin, such as 1,000 mg daily, to treat high cholesterol.

High doses of niacin may help lower the risk of heart attack and stroke in people with plaque buildup in the arteries.

High levels of niacin, as nicotinic acid, can help reduce low-density lipoprotein (LDL), or “bad” cholesterol, raise high-density lipoprotein (HDL), or “good” cholesterol, and reduce triglyceride levels.

However, high doses of niacin are unsuitable for people taking statins.

Niacin flush is harmless. It may cause discomfort, but it doesn’t damage the body. This flushing will usually go away without treatment within 1–2 hours.

As people continue to take niacin, they may find that the intensity of niacin flush reduces.

According to the NIH, niacin supplements of 30 mg or more may cause headaches, rashes, or dizziness.

Taking high doses of niacin of 1,000 mg or more without the approval of a doctor may have harmful side effects, such as:

  • low blood pressure, which may increase the risk of falling
  • fatigue
  • high blood sugar levels
  • nausea
  • heartburn
  • abdominal pain
  • blurred vision and buildup of fluid in the eyes

Inositol nicotinate, or inositol hexanicotinate, is a combination of a form of niacin and inositol, a type of sugar that occurs in the body.

Retailers may sell inositol nicotinate as “no-flush” niacin. It may reduce flushing symptoms compared with other forms of niacin, as the body takes longer to break it down. Inositol nicotinate also lowers LDL cholesterol and triglycerides and increases HDL cholesterol.

Other sources suggest that although inositol nicotinate reduces or prevents flushing, it may not provide the body with high enough levels of niacin to lower cholesterol.

Niaspan is a prescription, slow-release form of nicotinic acid. It may reduce flushing and still provide benefits for lowering cholesterol. However, it may be more expensive than other forms of niacin.

Niaspan releases niacin more slowly but over a shorter period than other extended-release forms. This means there is less pressure on the liver to process niacin, reducing the risk of liver damage.

If people take immediate-release niacin with food, it may help decrease the intensity of niacin flush symptoms.

People may also find they can minimize flushing by starting with a lower dose of niacin and gradually working up to higher doses over the following weeks.

For example, individuals may take 100 mg of niacin twice daily with meals for the first week, then double the daily amount each week until they reach the prescribed amount. People can discuss with a healthcare professional whether this is safe for them.

According to a 2017 study, taking aspirin alongside niacin may help reduce the effects of flushing.

People can speak with a healthcare professional about the safety of taking aspirin or other medications alongside prescription niacin.

Niacin occurs naturally in many foods, including:

  • poultry
  • fish
  • legumes
  • fortified foods, such as cereals and bread

According to the NIH, niacin supplements come in two main forms: nicotinic acid and nicotinamide.

Nicotinic acid is the form of niacin that doctors prescribe to treat high cholesterol.

Extended-release nicotinic acid releases niacin more slowly into the body over an extended period. Long-term use of high niacin doses and extended-release forms of nicotinic acid may cause liver damage, including hepatitis and liver failure.

Nicotinamide may not cause as many side effects as nicotinic acid. However, doses of 500 mg or more each day may cause diarrhea, easy bruising, and increased wound bleeding.

Doses of 3,000 mg or more daily may cause nausea, vomiting, and liver damage.

Niacin flush is the skin flushing after taking high doses of niacin. Most people will experience this side effect.

People may take higher doses of prescription niacin to treat high cholesterol. Without supervision from a doctor, high doses of niacin may cause harmful side effects.

Niacin flush may also cause a tingling, pricking, or burning sensation and may affect the skin on the face and upper body. It is harmless and usually resolves without intervention within a few hours.

The intensity of niacin flush may vary with different forms of niacin. People may find that increasing dosage slowly to the prescribed amount or taking niacin with food may help reduce symptoms.

zastosuvannya, side effects, guarded by vikoristannya, melancholy and bad health

Nicotinic acid (niacin) is a water-soluble vitamin, belongs to the family of B vitamins, which is found in many tissues of animals and plants, has antihyperlipidemic activity. Niacin is converted to its active form, niacinamide, which is a component of the coenzymes nicotinamide adenine dinucleotide (NAD) and its phosphate form, NADP. These coenzymes play an important role in tissue respiration and the metabolism of glycogen, lipids, amino acids, proteins, and purine. Although the exact mechanism of action by which nicotinic acid lowers cholesterol levels is not well understood, this substance may act by inhibiting very low density lipoprotein (VLDL) synthesis, inhibiting the release of free fatty acids from adipose tissue, increasing lipoprotein lipase activity, and decreasing hepatic synthesis. VLDL-C and LDL-C.

Niacin, also known as nicotinic acid and vitamin B3, is a water-soluble, essential B vitamin that, when given in high doses, is effective in lowering low-density lipoprotein (LDL) cholesterol and increasing high-density lipoprotein (HDL) cholesterol, due to which this remedy acquires unique values ​​in the treatment of dyslipidemia. Niacin can cause mild to moderate elevations in serum aminotransferase levels, and high doses of certain forms of niacin are associated with clinically apparent, acute liver injury that can be both severe and fatal.

Niacin (nicotinic acid) is used to prevent and treat niacin deficiency (pellagra). Niacin deficiency can result from certain medical conditions (eg, alcohol abuse, malabsorption syndrome, Hartnup’s disease), poor diet, or long-term use of certain medications (eg, isoniazid).

Products containing vitamin B3

  • avocado
  • broccoli
  • tomatoes
  • mushrooms
  • asparagus
  • carrots
  • rice
  • legumes
  • spinach
  • sweet potato

Niacin deficiency can cause diarrhea, confusion (dementia), redness/swelling of the tongue, and scaling of hard red skin. Nicotinic acid helps support the body’s ability to produce and break down natural compounds (metabolism) needed for good health. Niacinamide (nicotinamide) is another form of vitamin B3, but it does not work in the same way as niacin.

Side effects of niacin use

Face and neck irritation, headache, itching, burning, sweating, chills or tingling may occur within 20 minutes to 4 hours after taking this drug. Irritation may continue for several hours. These effects should fade or fade as your body adjusts to the medication. Indigestion, heartburn, nausea, vomiting, and diarrhea may also occur. If any of these effects persist or worsen, tell your doctor or pharmacist immediately.

Veterinary Niacin

Like most animals, dogs can synthesize a certain amount of niacin from the essential amino acid tryptophan. The tryptophan metabolite can be formed in one of two ways: it can be formed by picolinic carboxylase, or it can be used to produce nicotinamide. Cats, unlike dogs, are not able to synthesize significant amounts of niacin from tryptophan because they have a very high activity of the enzyme picolinic carboxylase, which leads to the rapid catabolism of tryptophan. Thus, cats require a diet of pre-prepared niacin.

Dietary sources of nicotinic acid

Niacin occurs naturally in meat and legumes. Dietary niacin is commonly found in the form of nicotinic acid in plant materials, and as NAD or NADP in animal materials. Some wholegrain cereals, such as corn and sorghum, have a relatively high niacin content, but in these products, niacin is concentrated in the seed and germ layers and has poor bioavailability (i.e., bound within the cell), making the feed a poor source of dietary niacin. Niacin is also sensitive to heat breakdown and commercial feed additives are needed to keep it stable.

Diagnosis of niacin deficiency

Diagnosis of niacin deficiency can be made using the nicotinamide test, which measures urinary excretion of niacin metabolites, the test itself takes place in veterinary control laboratories. Diagnosis is also made by clinical signs, appropriate deficiency and dietary assessment.

The role of nicotinic acid in the animal body

  • Metabolic function Niacin derivatives are a necessary cofactor in dehydrogenase / reductase reactions. Niacin itself is used in catabolic reactions associated with the metabolism of glucose, fatty acids, ketones and amino acids, the synthesis of lipids and cholesterol.
  • Uses: High dose nicotinic acid supplementation has been shown to reduce low density lipoprotein and very low density lipoprotein while increasing high density lipoprotein cholesterol levels. Niacin supplementation is suggested in treatment to reduce hypercholesterolemia in dogs and has been shown to result in decreased VLDL synthesis in obese dogs.
  • Vitamin B3 – nicotinamide, plasma (Vitamin PP, niacin, Vitamin B3 – Nicotinamide, Niacinamide, plasma)

    Method of determination
    HPLC-MS (High Performance Liquid Chromatography with Mass Selective Detection).

    Test material
    Blood plasma (EDTA)

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    Synonyms: Nicotinic acid; Vitamin PP; Antipellagric factor; 3-pyridinecarboxylic acid.

    Niacin; Vitamin B3; Nicotinicacid; Vitamin PP; Pyridine-3-carboxylicacid; 3-pyridinecarboxylicacid; Apelagrin; Pellagrin.

    Brief description of the analyte Vitamin B3 – nicotinamide

    Vitamin B3 includes two main forms – nicotinamide and nicotinic acid. During metabolic processes in the body, they are converted into nicotinamide adenine dinucleotide (NAD, nicotinamide adenine dinucleotide – NAD) and nicotinamide adenine dinucleotide phosphate (NADP, nicotinamide adenine dinucleotide phosphate – NADP) – coenzymes of many redox reactions that are vital for cellular metabolism.

    Nicotinamide is important for the development and functioning of the central nervous system (CNS). Nicotinamide is believed to play an important role in protecting neurons from traumatic injury, ischemia, and stroke, and may be involved in the pathogenesis of the three most common neurodegenerative conditions: Alzheimer’s, Parkinson’s, and Huntington’s diseases. The key factor here is the bioavailability of nicotinamide, a low concentration of which can lead to neurological deficits and dementia, and a high concentration can lead to potential neurotoxicity. B3 deficiency in its classical form is manifested by pellagra, and one of the common names for this vitamin “PP” comes from pellagra prevention – preventing pellagra. Clinical manifestations of this disease include bilateral symmetrical dermatitis on areas of the skin exposed to sunlight; extensive inflammation of the mucous membranes, manifested by diarrhea, achlorhydria, glossitis, stomatitis, vaginitis; mental manifestations, including fatigue, insomnia, apathy, in severe cases, encephalopathy with disorientation, hallucinations, memory loss, psychosis and dementia.

    The main dietary sources of vitamin B3 are foods containing yeast, lean meats, liver, and poultry. Smaller amounts of this vitamin (but sufficient to avoid deficiency) are found in milk, various green leafy vegetables, and canned salmon. In some plant foods, especially in cereals (corn, wheat), niacin is associated with peptides and sugars and is less available for absorption. Up to two-thirds of the required amount of vitamin B3 in adults can be formed in the body itself through the metabolism of tryptophan.

    Nutritional deficiency of B3 is associated with a lack of protein food and is rare in developed countries, it can more often occur with a predominance of corn (maize) in the diet, which is poor in both niacin and tryptophan. Pellagra can sometimes be a secondary manifestation of the carcinoid syndrome, in which up to 60% of tryptophan is catabolized into 5-OH-tryptophan and serotonin; and Hartnup’s disease, a genetic disorder associated with malabsorption of amino acids, including tryptophan.

    Vitamin deficiency can be caused by alcoholism, the action of certain drugs. A complicating factor may be a deficiency of vitamins B2, B6 and iron, which are involved in the conversion of tryptophan to niacin.

    What is the purpose of determining the level of vitamin B3 in the blood?

    The test is used to assess the status of vitamin B3 in the body.

    Vitamin B3 preparations are used in medical practice, including nicotinamide, in the treatment of pellagra, carcinoid syndrome, Hartnup’s disease, nicotinic acid – in lipid-lowering therapy, using the range of its effects on lipid metabolism.