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Overview: Niacin is used to increase vitamin B3 levels, lower cholesterol and triglyceride levels, and lower your risk of certain serious heart problems. Common side effects include flushing, nausea, vomiting, and diarrhea. Serious side effects are less common but may include liver damage or muscle problems. Notify your health care provider right away if you lose your appetite, have unusual weakness or tiredness, or have unexplained muscle pain.

Uses

What is niacin used for?

Niacin is commonly used for the following. 

These uses may vary depending on the specific niacin product prescribed or taken. 

Niacin may also be used for other conditions as determined by your health care provider.

How does niacin work (mechanism of action)?

Niacin, which is a form of vitamin B3, can help to increase levels of vitamin B3 in the body. It works in many ways to help improve lipid levels in your blood, including cholesterol and triglycerides. It reduces how much of these are made in the liver. It slows down the release of lipids from the liver into the blood. Niacin also increases how quickly the body breaks down the lipids in the blood.

How is niacin supplied (dosage forms)?

Brands and other names

  • Niacor
  • Niaspan
  • Nicolar
  • Slo Niacin
  • Wampocap

Niacin, also known as vitamin B3, is available as a dietary supplement in various strengths and dosage forms to supplement levels of this vitamin. Niacin is also available as a prescription to treat high blood cholesterol levels in the following dosage forms and strengths.

  • 500 mg oral tablets
  • 500 mg, 750 mg, 1000 mg extended-release oral tablets

Niacin for vitamin supplementation is also available in another form. See niacinamide for more information.

How should I store niacin?

Niacin should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Side Effects

What are the most common side effects of niacin?

The most common side effects of niacin are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Flushing 
  • Diarrhea
  • Nausea or vomiting
  • Cough
  • Itching or rash

There may be other side effects of niacin that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of niacin?

While less common, the most serious side effects of niacin are described below, along with what to do if they happen.

Severe Allergic Reactions. Niacin may cause allergic reactions, which can be serious. Stop taking niacin and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives, which can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Liver Damage. Liver damage, also called hepatotoxicity, can happen when taking niacin. This may be more likely if you have a history of liver problems, drink large amounts of alcohol, take extended-release niacin, or switch between niacin products. Call your health care provider right away if you have any of the following symptoms of liver damage.

  • Nausea or vomiting
  • Stomach or belly pain
  • Fever
  • Weakness or unusual tiredness
  • Itching
  • Loss of appetite
  • Light-colored poop
  • Dark-colored urine (pee)
  • Your skin or the whites of your eyes turning yellowish (also called jaundice)

Muscle Problems. Niacin can cause muscle problems, including muscle pain, weakness, and tenderness, called myopathy. Your risk may be higher if you have diabetes, thyroid problems, or kidney problems. In some people, the muscle may break down (rhabdomyolysis), which can be serious and rarely leads to kidney damage and death. Stop taking niacin and get help right away if you have any of the following symptoms of myopathy or rhabdomyolysis.

  • Unexplained muscle pain, weakness, or tenderness
  • Low energy levels or feeling easily tired, especially with activity
  • Dark-colored urine (pee)
  • Fever
  • Muscle cramps
  • Stomach pain
  • Nausea or vomiting

High Blood Sugar. Niacin may increase your blood sugar levels. Talk to your health care provider about how to maintain healthy blood sugar levels. Keep all appointments with your health care provider for blood tests. Call your health care provider if you have the following symptoms of high blood sugar.

  • Thirsty more than usual
  • Peeing more than usual
  • Increase in hunger
  • Tiredness
  • Feeling sick to your stomach
  • Confusion
  • Your breath smelling fruity

Low Blood Pressure (Hypotension). Niacin may cause low blood pressure. This can sometimes lead to falls. If you feel faint or dizzy, lie down. Tell your health care provider right away if you have any of the following symptoms of low blood pressure.

  • Dizziness, feeling lightheaded, or fainting
  • Confusion
  • Feeling weak or tired

Vision Problems. Niacin may increase your risk of macular edema. Macular edema happens when fluid builds up in the back of your eye. Keep any scheduled eye exams before starting or while taking niacin. Call your health care provider right away if you have any of the following symptoms of macular edema.

  • Blurriness or shadows 
  • Sensitivity to light
  • Worsening vision
  • A blind spot in the middle of your vision
  • Dull or unusually colored or tinted vision

Warnings & Precautions

Who should not use niacin?

Allergies to Ingredients. People who are allergic to any of the following should not take niacin.

  • Niacin
  • Niacor
  • Niaspan
  • Nicolar
  • Nicotinic acid
  • Slo Niacin
  • Wampocap
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific niacin products they stock.

Liver Problems. Niacin should not be used if your liver is not working as well as it should be. If there is a concern about the health of your liver, your health care provider may do tests to see if it is working well enough to take this medicine.

Stomach Ulcer. Niacin should not be used if you have a stomach ulcer. 

Bleeding Problems. Niacin should not be used if you have bleeding problems. 

What should I know about niacin before using it?

If niacin was prescribed to you by a health care provider, use it as prescribed. If you are using over-the-counter niacin, follow the instructions that come with the product.

Do not share niacin that was prescribed for you by a health care provider with other people, even if they have the same condition as you. It may harm them.

Keep niacin out of the reach of children.

It may be best to start with a low dose of niacin and slowly increase it over time in order to reduce your risk of side effects. Taking niacin with or after food or a snack may also reduce your risk of side effects. If you are not sure how to take your niacin, ask your pharmacist or other health care provider. 

You should not stop taking niacin without talking to your health care provider. If you have to stop taking niacin for any reason and need to restart it, you may need to start over with a low dose and slowly increase it over time. Check with your health care provider if you are not sure. 

Niacin extended-release tablets should not be chewed, crushed, or broken. They should be swallowed whole. Do not switch between different forms of niacin. The products may not be equal, even if you take the same dose. Also, although dietary supplements containing niacin and niacinamide may be used for similar reasons, they are not the same. Talk with your health care provider if you want to change to a different niacin product.

Flushing is normal with niacin, especially with doses higher than normal daily intake from food. It can lead to redness, a warm tingly feeling, or itching. Flushing is more common when you first start taking niacin or when your dose is increased. If you wake up during the night with flushing, get up slowly, especially if you take medicines to lower your blood pressure or feel dizzy or like you are going to faint. Notify your health care provider if you have dizziness with niacin. Taking niacin at bedtime can be helpful, as you may sleep through the flushing. Flushing usually decreases over time. Try to avoid hot drinks, spicy food, and alcohol near the time you take your niacin. These things can increase your risk of flushing. If you have trouble tolerating the flushing, ask your health care provider if it is okay for you to take aspirin about 30 minutes before your niacin to reduce flushing. 

It is important to know the difference between flushing from niacin and symptoms of a heart attack. Flushing happens because blood vessels get wider or open up. This can cause your skin to appear red, itchy, or warm. A heart attack happens when blood supply is cut off to part of the heart. Get medical help right away if you have any of the following symptoms, which may be a sign of a heart attack.

  • Chest pain or pressure
  • Fast or abnormal heartbeat
  • Trouble breathing
  • Pain in your back, jaw, throat, or arm
  • Sweating, upset stomach, or vomiting 
  • Dizziness or feeling lightheaded

What should I tell my health care provider before using niacin?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if niacin is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Gout
  • Gallbladder problems
  • Heart disease, including unstable angina or a recent heart attack
  • Kidney or liver problems
  • Drink large amounts of alcohol

Diabetes. Niacin can increase blood sugar levels. Tell your health care provider if you have changes in your blood sugar levels. Follow any instructions given to you about how often to check your blood sugar. 

Other Medicines and Supplements. Niacin may interact with other medicines and supplements. Before taking niacin, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how niacin could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant. Your health care provider will let you know if you should take niacin while you are pregnant or trying to get pregnant. 

Breastfeeding. Niacin passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should stop breastfeeding or stop niacin.

Interactions

Does niacin interact with foods or drinks?

Hot drinks or spicy foods can increase your risk of flushing. It is best to avoid these around the time you take niacin. Taking niacin with food may reduce flushing. Some niacin products should be taken with or after food and not on an empty stomach. Follow the instructions that come with your medicine. If you are not sure how to take your niacin, ask your pharmacist. 

Drinking alcohol around the same time you take niacin can increase your risk of flushing. Both niacin and alcohol can increase your risk of liver damage. It is best to limit the amount of alcohol you drink.

Does niacin interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking niacin.

  • A statin, such as atorvastatin (Lipitor and others) or rosuvastatin (Crestor), which is a medicine to lower cholesterol
  • A bile acid sequestrant, such as cholestyramine (Prevalite), colesevelam (Welchol), or colestipol (Colestid), which is a medicine to lower cholesterol
  • A medicine for high blood pressure
  • A blood thinner, which is a medicine used to treat or prevent blood clots
  • A vitamin or supplement containing niacin, nicotinic acid, or niacinamide

This may not be a complete list of medicines that can interact with niacin. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much niacin?

If you or someone else has used too much niacin, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of niacin?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.