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

Niacin deficiency can cause diarrhea, confusion (dementia), tongue redness/swelling, and peeling red skin. Niacin is also known as vitamin B3, one of the B-complex vitamins. Vitamins help to support the body's ability to make and break down natural compounds (metabolism) needed for good health. Niacinamide (nicotinamide) is a different form of vitamin B3 and does not work the same as niacin. Do not substitute unless directed by your doctor.

Check the ingredients on the label even if you have used the product before. The manufacturer may have changed the ingredients. Also, products with similar names may contain different ingredients meant for different purposes. Taking the wrong product could harm you.

This section contains uses of this drug that are not listed in the approved professional labeling for the drug, but may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This product may also be used to improve cholesterol and lower fat levels (triglycerides) in the blood under the care of your doctor. It is generally used after non-drug treatments have not been fully successful at lowering cholesterol. Doses used for these blood fat problems are usually much higher than for dietary problems.

Take this medication by mouth with a low-fat meal or snack as directed by your doctor, usually 1-3 times daily. Taking niacin on an empty stomach increases side effects (such as flushing, upset stomach). Follow all directions on the product package. If your doctor has prescribed this medication, take it as directed. If you have any questions, ask your doctor or pharmacist.

Niacin is available in different formulations (such as immediate and sustained release). Do not switch between strengths, brands, or forms of niacin. Severe liver problems may occur.

Swallow extended-release capsules whole. Do not crush or chew extended-release capsules or tablets. Doing so can release all of the drug at once, increasing the risk of side effects. Also, do not split extended-release tablets unless they have a score line and your doctor or pharmacist tells you to do so. Swallow the whole or split tablet without crushing or chewing.

To lessen the chance of side effects such as flushing, avoid alcohol, hot beverages, and eating spicy foods near the time you take niacin. Taking a plain (non-enteric coated, 325 milligram) aspirin or a nonsteroidal anti-inflammatory drug (such as ibuprofen, 200 milligrams) 30 minutes before taking niacin may help prevent flushing. Ask your doctor if this treatment is right for you.

If you also take certain other drugs to lower cholesterol (bile acid-binding resins such as cholestyramine or colestipol), take niacin at least 4 to 6 hours before or after taking these medications. These products interact with niacin, preventing its full absorption. Continue to take other medications to lower your cholesterol as directed by your doctor.

The dosage is based on your medical condition and response to treatment. If you are taking this for lipid problems, your doctor may direct you to start this medication at a low dose and gradually increase your dose to reduce your risk of side effects. Your dose will need to be increased slowly even if you are already taking niacin and are being switched from another niacin product to this product. Follow your doctor's instructions carefully.

Do not stop taking this medicine unless instructed by your doctor. If you stop taking niacin, you may need to return to your original dose and gradually increase it again. Ask your doctor or pharmacist for instructions on restarting your dose if you have not taken your medication for several days.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time(s) each day.

It is very important to continue to follow your doctor's advice about diet and exercise.

If your condition lasts or gets worse, or if you think you may have a serious medical problem, get medical help right away.

Flushing/warmth in the face and neck, headache, itching, burning, sweating, chills, or tingling may occur within 20 minutes to 4 hours of taking this medication. Flushing may last for a few hours. These effects should improve or go away as your body adjusts to the medication. Stomach upset, heartburn, nausea, vomiting, and diarrhea may also occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position. This is very important if you are also taking medication to lower your blood pressure.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• nausea/vomiting that doesn't stop
• fast/irregular heartbeat
• severe headache (migraine)
• unusual joint pain
• swelling of legs/arms
• vision problems
• severe stomach/abdominal pain
• black stools
• easy bruising/bleeding
• unexplained muscle pain/tenderness/weakness
• signs of kidney problems (such as change in the amount of urine)
• dark urine
• vomit that looks like coffee grounds
• yellowing eyes/skin

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking niacin, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

If you have any of the following health problems, consult your doctor or pharmacist before using this medication:

• very low blood pressure
• alcohol use
• history of bleeding problems (such as low platelets)
• diabetes
• gallbladder disease
• glaucoma
• gout
• heart disease (such as recent heart attack, unstable angina)
• kidney disease
• liver disease/increase in liver enzymes
• untreated mineral imbalance (low phosphate levels)
• stomach/intestinal ulcers
• underactive thyroid (hypothyroidism)

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

This medication may rarely make your blood sugar rise, which can cause or worsen diabetes. If you already have diabetes, check your blood sugar regularly as directed and share the results with your doctor. Tell your doctor right away if you have symptoms of high blood sugar such as increased thirst/urination. Your doctor may need to adjust your diabetes medication, exercise program, or diet.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

This medication passes into breast milk. Consult your doctor before breastfeeding.

See also How to Use section.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Check all prescription and nonprescription medicine labels carefully since vitamins/dietary supplements may also contain niacin or niacinamide (nicotinamide). These may increase your risk of side effects if taken together. Ask your doctor or pharmacist for more details.

This medication may interfere with certain lab tests (such as urine or blood catecholamines, copper-based urine glucose tests), possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

If you are taking this for high cholesterol, in addition to eating a proper diet (such as a low-cholesterol/low-fat diet), other lifestyle changes that may help this medication work better include exercising, losing weight if overweight, and stopping smoking. Consult your doctor for more details.

Remember that it is best to get your vitamins and minerals from food whenever possible. Maintain a well-balanced diet, and follow any dietary guidelines as directed by your doctor. B vitamins (including niacin) are found in meat, fish, poultry, enriched/whole grain bread products, and fortified cereals. Eat more of these foods to increase the amount of niacin in your diet if you have a niacin deficiency.

There are many niacin products available. Some can be purchased without a prescription. Consult your doctor or pharmacist about the best product for you.

Lab tests (such as blood lipids, blood sugar, liver function, uric acid levels) may be done (especially if prescribed for cholesterol/triglyceride control) while you are taking this product. Keep all medical and lab appointments. Consult your doctor for more details.

Do not share this medication with others.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from moisture and light. Do not store in the bathroom. Refer to storage information printed on the package. If you have any questions about storage, ask your pharmacist. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.