Herb & supplement monograph

Niacin Drug Interactions, Uses, Effectiveness, Safety & More

Q: What is Niacin used for, and does it work?

People use Niacin for many reasons, but the evidence varies by use. According to the Natural Medicines database, there is at least some clinical evidence supporting Niacin for Pellagra, HIV/AIDS-related dyslipidemia and Metabolic syndrome. For most other uses it has been studied for, the evidence is currently insufficient to rate. See the graded list on this page, and always confirm with your pharmacist or doctor.

Q: Does Niacin interact with prescription medications?

Yes. We list 729 medications with a known interaction with Niacin. Use the checker above to see how Niacin interacts with a specific drug.

Q: How are Niacin interactions rated?

Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.

Q: Is it safe to take Niacin with my medications?

It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.

Q: Where does this Niacin interaction information come from?

Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.

Q: What is Niacin used for?

Niacin (vitamin B3) is needed to turn food into energy and to prevent its deficiency disease, pellagra. High-dose prescription Niacin has also been used to help adjust cholesterol levels, though this use is less common now.

Q: Why does Niacin make my skin flush and turn red?

Higher doses of nicotinic acid can release substances that widen blood vessels near the skin, causing warmth, redness, tingling, or itching. Taking it with food or using an extended-release form may help reduce this.

Q: Can I get enough Niacin from food?

Yes. Most people in developed countries get enough Niacin from foods like meat, fish, poultry, peanuts, and fortified grains, so deficiency is uncommon.

Q: Is high-dose Niacin safe to take on my own?

High-dose Niacin can cause flushing, stomach upset, liver problems, and other effects, so it should only be taken under the guidance of a doctor or pharmacist.

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Niacin interacts with medications. The heart of this page is the interaction list — every drug Niacin is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Niacin is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Niacin Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the risk of a clinically significant Niacin drug interaction is moderate for most people, particularly when niacin is taken in high doses. None of the listed interactions are rated major, but nearly all are moderate, and several are backed by human studies rather than theory alone.

Interactions deserving the most attention

The best-documented concern is with diabetes medications, since niacin can raise blood sugar and make these drugs work less well, an effect shown in human studies. Niacin can also lower thyroxine levels, so people on thyroid hormone may notice a change in how well it works. It may also reduce the effect of gout medications such as allopurinol and probenecid by raising uric acid levels. Combining niacin with alcohol can worsen flushing and stress the liver, and a case report links niacin to a stronger effect from warfarin.

What the rest of the list means

Although the full list of interacting medications is long, most entries reflect a shared concern, such as effects on blood sugar, blood pressure, or the liver, rather than a unique problem with each drug. Many of these effects are theoretical or tied to large, prescription-strength doses of niacin, and some predicted problems, like muscle damage with statins, have not been confirmed in clinical trials.

Check your medications against Niacin

Based on HelloPharmacist’s Niacin interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Niacin

729 medications have a known interaction with Niacin, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Niacin using our pharmacist-reviewed interaction data.

AI summaries are generated from our Niacin interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Niacin combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Niacin affects

Every type of medication (drug category) Niacin is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 15 drug categories Niacin interacts with

Alcohol (ethanol)Allopurinol (zyloprim)Anticoagulant/antiplatelet DrugsAntidiabetes DrugsAntihypertensive DrugsBile Acid SequestrantsGemfibrozil (lopid)Hepatotoxic DrugsHmg-coa Reductase Inhibitors ("statins")Probenecid (benemid)Sulfinpyrazone (anturane)Thyroid HormoneTransdermal Nicotine (nicoderm)Warfarin (coumadin)Aspirin

Alcohol (Ethanol)

Concomitant use of alcohol and niacin might increase the risk of flushing and hepatotoxicity.
Alcohol can exacerbate the flushing and pruritus associated with niacin. Large doses of niacin might also exacerbate liver dysfunction associated with chronic alcohol use. A case report describes delirium and lactic acidosis in a patient taking niacin 3 grams daily who ingested 1 liter of wine. Advise patients to avoid large amounts of alcohol while taking niacin.

Likelihood Probable Evidence D

Allopurinol (Zyloprim)

Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as allopurinol.
Large doses of niacin can reduce urinary excretion of uric acid, potentially resulting in hyperuricemia. Doses of uricosurics such as allopurinol might need to be increased to maintain control of gout in patients who start taking niacin. People who have frequent attacks of gout despite uricosuric therapy should avoid niacin.

Likelihood Probable Evidence C

Anticoagulant/Antiplatelet Drugs

Theoretically, niacin may have additive effects when used with anticoagulant or antiplatelet drugs.
Several cases of clotting factor synthesis deficiency and coagulopathy have been reported in patients taking sustained-release niacin. Also, thrombocytopenia has been reported in patients treated with niacin or niacin plus lovastatin.

Likelihood Possible Evidence D

Antidiabetes Drugs

Niacin can increase blood glucose levels and may diminish the effects of antidiabetes drugs.
Niacin impairs glucose tolerance in a dose-dependent manner, probably by causing or aggravating insulin resistance and increasing hepatic production of glucose. In diabetes patients, niacin 4.5 grams daily for 5 weeks can increase plasma glucose by an average of 16% and glycated hemoglobin (HbA1c) by 21%. However, lower doses of 1.5 grams daily or less appear to have minimal effects on blood glucose. In some patients, glucose levels increase when niacin is started, but then return to baseline when a stable dose is reached. Up to 35% of patients with diabetes may need adjustments in hypoglycemic therapy when niacin is added.

Likelihood Probable Evidence B

Antihypertensive Drugs

Theoretically, niacin may increase the risk of hypotension when used with antihypertensive drugs.
The vasodilating effects of niacin can cause hypotension. Furthermore, some clinical evidence suggests that a one-hour infusion of niacin can reduce systolic, diastolic, and mean blood pressure in hypertensive patients. This effect is not observed in normotensive patients.

Likelihood Possible Evidence B

Bile Acid Sequestrants

Bile acid sequestrants can bind niacin and decrease absorption. Separate administration by 4-6 hours to avoid an interaction.
In vitro studies show that colestipol (Colestid) binds about 98% of available niacin and cholestyramine (Questran) binds 10% to 30%.

Likelihood Possible Evidence D

Gemfibrozil (Lopid)

Theoretically, concomitant use of niacin and gemfibrozil might increase the risk of myopathy in some patients.
A case of myopathy from concomitant use of niacin and gemfibrozil has been reported. Niacin alone has also been associated with cases of myopathy. Using gemfibrozil with niacin might further increase the risk of developing myopathy.

Likelihood Possible Evidence D

Hepatotoxic Drugs

Theoretically, concomitant use of niacin and hepatotoxic drugs might increase the risk of hepatotoxicity.
Niacin has been associated with cases of liver toxicity, especially when used in pharmacologic doses. Sustained-release niacin preparations appear to be associated with a higher risk of hepatotoxicity than immediate-release niacin.

Likelihood Possible Evidence D

Hmg-Coa Reductase Inhibitors ("Statins")

Theoretically, concomitant use of niacin and statins might increase the risk of myopathy and rhabdomyolysis in some patients.
Some case reports have raised concerns that niacin might increase the risk of myopathy and rhabdomyolysis when combined with statins. However, a significantly increased risk of myopathy has not been demonstrated in clinical trials, including those using an FDA-approved combination of lovastatin and niacin (Advicor).

Likelihood Possible Evidence D

Probenecid (Benemid)

Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as probenecid.
Large doses of niacin reduce urinary excretion of uric acid, potentially causing hyperuricemia. Doses of uricosurics such as probenecid might need to be increased to maintain control of gout in patients who start taking niacin. People who have frequent attacks of gout despite uricosuric therapy should avoid niacin.

Likelihood Probable Evidence C

Sulfinpyrazone (Anturane)

Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as sulfinpyrazone.
Large doses of niacin reduce urinary excretion of uric acid, potentially causing hyperuricemia. Doses of uricosurics such as sulfinpyrazone might need to be increased to maintain control of gout in patients who start taking niacin. People who have frequent attacks of gout despite uricosuric therapy should avoid niacin.

Likelihood Probable Evidence C

Thyroid Hormone

Theoretically, niacin might antagonize the therapeutic effects of thyroid hormones.
Clinical research and case reports suggests that taking niacin can reduce serum levels of thyroxine-binding globulin by up to 25% and moderately reduce levels of thyroxine (T4). Patients taking thyroid hormone for hypothyroidism might need dose adjustments when using niacin.

Likelihood Probable Evidence D

Transdermal Nicotine (Nicoderm)

Theoretically, concomitant use of niacin and transdermal nicotine might increase the risk of flushing and dizziness.
Niacin and nicotine can both cause flushing and dizziness.

Likelihood Possible Evidence D

Warfarin (Coumadin)

There is limited evidence that niacin may increase the anticoagulant effects of warfarin.
In a case report, a patient on warfarin developed an elevated international normalized ratio (INR) of 3.9 after taking niacin for two weeks. The patient's INR was previously stable, ranging between 2 and 3 in recent months, and no other medication changes were identified. The elevated INR returned to therapeutic range within 4 days following the discontinuation of niacin.

Likelihood Possible Evidence D

Aspirin

Large doses of aspirin might alter the clearance of niacin.
Aspirin is often used with niacin to reduce niacin-induced flushing. Doses of 80-975 mg aspirin have been used, but 325 mg appears to be optimal. Aspirin also seems to reduce the clearance of niacin by competing for glycine conjugation. Taking aspirin 1 gram seems to reduce niacin clearance by 45%. This is probably a dose-related effect and not clinically significant with the more common aspirin dose of 325 mg.

Likelihood Likely Evidence B

Monograph

Niacin: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Niacin (vitamin B3) is an essential nutrient your body needs for energy and metabolism, and deficiency is uncommon in most developed countries. Prescription-strength niacin has been used to adjust cholesterol levels, but high doses can cause flushing and other side effects and should only be taken under medical supervision. Always talk with a pharmacist or doctor before using high-dose niacin supplements.

Part used: Not applicable (a vitamin, not a plant part)
Common forms: Tablets, extended-release tablets, capsules; also found in multivitamins and food

People commonly use it for

High cholesterol
Vitamin B3 deficiency (pellagra)
Heart health support
General energy and metabolism

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Normal dietary amounts are safe, but high supplemental doses can cause flushing, liver problems, and other effects.

PregnancyLikely Safe

When used orally in amounts that do not exceed the tolerable upper intake level (UL). The UL of niacin during pregnancy and lactation is 30 mg daily f...

Read the full pregnancy detail

BreastfeedingLikely Safe

When used orally in amounts that do not exceed the tolerable upper intake level (UL). The UL of niacin during pregnancy and lactation is 30 mg daily f...

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Niacin, also called vitamin B3, is a water-soluble vitamin that your body needs to work properly. It is found naturally in many foods, including meat, poultry, fish, peanuts, and fortified grains and cereals. Because it is water-soluble, your body does not store large amounts of it, so you need a steady supply from food.

Your body can also make small amounts of niacin from an amino acid called tryptophan. Niacin comes in a few different chemical forms, including nicotinic acid, niacinamide (nicotinamide), and related compounds like nicotinamide riboside. These forms can behave differently in the body.

People use niacin to prevent or treat deficiency, and high doses of one form (nicotinic acid) have been used as a prescription medicine to help manage cholesterol levels.

How it works

Niacin is a building block for two important molecules in the body called NAD and NADP. These molecules help hundreds of chemical reactions, especially those that turn the food you eat into energy. They are involved in the metabolism of carbohydrates, fats, and proteins.

In higher, drug-like doses, nicotinic acid affects how the liver makes and clears fats and cholesterol in the blood. This is thought to be why it can change cholesterol and triglyceride levels. The flushing many people feel is caused by the release of substances that widen blood vessels in the skin.

Much of what we know comes from human nutrition research, but some proposed effects are based on laboratory or smaller studies and are still being explored.

Effectiveness

Does Niacin work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 23 uses evaluated

1 Likely effective 2 Possibly effective 1 Ineffective 19 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

Likely Effective Pellagra