Drug & supplement interaction

Niacin + Metformin, Rosiglitazone

Metformin, Rosiglitazone brand name: Avandamet.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Metformin, Rosiglitazone falls into 2 drug categories that Niacin can interact with; the most serious is rated moderate. Theoretically, concomitant use of niacin and hepatotoxic drugs might increase the risk of hepatotoxicity.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Niacin and Metformin, Rosiglitazone

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Niacin interacts with whole categories of medication. Metformin, Rosiglitazone falls into 2 of those categories, so it can interact with Niacin in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

HEPATOTOXIC DRUGS

1 of 2

Why this applies to Metformin, Rosiglitazone

Metformin, Rosiglitazone falls under HEPATOTOXIC DRUGS — the group Niacin interacts with.

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.
Severity Moderate Likelihood Possible Evidence D

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.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist with Avandamet (the metformin and rosiglitazone combo) and high-dose niacin: this isn't about niacin changing your blood sugar pill levels. The concern is the liver. Both high-dose niacin (especially the sustained-release kind) and rosiglitazone can, in rare cases, stress the liver. Stacking two things that lean on the liver could, in theory, add up.

I want to be honest that this is a theoretical caution based on how these work, not something proven to commonly happen. Everyday food amounts of niacin and a normal multivitamin won't matter here. The worry is concentrated, drug-strength niacin doses. If you take that kind, please loop in your doctor or pharmacist so they can keep an eye on your liver labs.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. American Society of Health-System Pharmacists. ASHP Therapeutic Position Statement on the safe use of niacin in the management of dyslipidemias. Am J Health Syst Pharm 1997;54:2815-9. DOI
  2. Bays HE, Dujovne CA. Drug interactions of lipid-altering drugs. Drug Saf 1998;19:355-71. PubMed
  3. Rader JI, Calvert RJ, Hathcock JN. Hepatic toxicity of unmodified and time-release preparations of niacin. Am J Med 1992;92:77-81. PubMed
  4. Etchason JA, Miller TD, Squires RW, et al. Niacin-induced hepatitis: a potential side effect with low-dose time-release niacin. Mayo Clin Proc. 1991;66(1):23-8. PubMed
  5. Henkin Y, Johnson KC, Segrest JP. Rechallenge with crystalline niacin after drug-induced hepatitis from sustained-release niacin. JAMA. 1990;264(2):241-3. DOI
  6. Henkin Y, Oberman A, Hurst DC, Segrest JP. Niacin revisited: clinical observations on an important but underutilized drug. Am J Med. 1991;91(3):239-46. PubMed
  7. Bassan M. A case for immediate-release niacin. Heart Lung. 2012 Jan-Feb;41(1):95-8. PubMed
  8. Nawaz N, Mistretta T, Karime C, Lewis J, Wolf E. Cholestatic Drug-Induced Liver Injury in a Patient Taking High-Dose Niacin for Hyperlipidemia. J Investig Med High Impact Case Rep 2024;12:23247096231224349. PubMed
Moderate

ANTIDIABETES DRUGS

2 of 2

Metformin, Rosiglitazone also falls under 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.
Severity Moderate Likelihood Probable Evidence B

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..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the thing to keep in mind: Avandamet combines metformin and rosiglitazone, two medicines that work to lower your blood sugar. High-dose niacin can push in the opposite direction. It tends to make the body more resistant to insulin and prompts the liver to release more glucose, so your readings may creep up and your medication may not control your sugar as well as it did before.

The dose really matters here. Studies show large amounts (around 4.5 grams a day) can noticeably raise blood sugar and HbA1c, while smaller amounts (1.5 grams or less) usually have little effect. Some people see a temporary bump that settles once they're on a steady dose. If you're starting niacin, don't change anything on your own. Just check in with your pharmacist or doctor so they can watch your numbers and adjust if needed.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Knodel LC, Talbert RL. Adverse effects of hypolipidaemic drugs. Med Toxicol 1987;2:10-32. PubMed
  2. Garg A, Grundy SM. Nicotinic acid as therapy for dyslipidemia in non-insulin-dependent diabetes mellitus. JAMA 1990;264:723-6. DOI
  3. American Society of Health-System Pharmacists. ASHP Therapeutic Position Statement on the safe use of niacin in the management of dyslipidemias. Am J Health Syst Pharm 1997;54:2815-9. DOI
  4. Bays HE, Dujovne CA. Drug interactions of lipid-altering drugs. Drug Saf 1998;19:355-71. PubMed
  5. Kahn SE, Beard JC, Schwartz MW, et al. Increased B-cell secretory capacity as mechanism for islet adaptation to nicotinic acid-induced insulin resistance. Diabetes 1989;38:562-8.
  6. Schwartz ML. Severe reversible hyperglycemia as a consequence of niacin therapy. Arch Int Med 1993;153:2050-2. DOI
  7. McKenney J. New perspectives on the use of niacin in the treatment of lipid disorders. Arch Intern Med 2004;164:697-705. PubMed
  8. Guyton JR, Fazio S, Adewale AJ, Jensen E, Tomassini JE, Shah A, Tershakovec AM. Effect of extended-release niacin on new-onset diabetes among hyperlipidemic patients treated with ezetimibe/simvastatin in a randomized controlled trial. Diabetes Care. 2012 PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction 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.
  • PossibleInteraction 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.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Niacin Also Interacts With Other Medications

Niacin has 726 moderate known drug interactions in our database — the Metformin, Rosiglitazone one above is among them. If you take anything else, check it against the full list below.

Moderate 726 No known interaction 2,104 (incl. Metformin, Rosiglitazone)
Taking anything else?

Check Another of Your Medications Against Niacin

Covers the 2,830 medications we’ve checked against Niacin. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Metformin, Rosiglitazone

This page covers Niacin only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metformin, Rosiglitazone page lists 315 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Siberian Cocklebur (major), Wine (major) and Acai (moderate).

By severity: 4 major · 268 moderate · 43 minor.

From our pharmacist’s overview on the Metformin, Rosiglitazone page

“Avandamet pairs metformin with rosiglitazone to manage type 2 diabetes, and its supplement list calls for genuine care rather than a quick skim. Start with the four major-rated entries: alcohol and the herb Siberian cocklebur can each stress the liver, a serious concern with rosiglitazone on board, while activated charcoal can soak up…”

Reviewed by 2 · Jul 18, 2026

Open the Metformin, Rosiglitazone interaction page

One more smart check

Taking Niacin as Part of a Dietary Supplement Product? Check It for Interactions

We hold 933 real supplement products containing Niacin, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Niacin. Your product may carry other ingredients that interact with Metformin, Rosiglitazone too, on top of Niacin — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Niacin and Metformin, Rosiglitazone Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Niacin
Top 25%

#205 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Metformin, Rosiglitazone
Steady interest

#1,789 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Niacin

What is Niacin?

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

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.

Read the full Niacin monograph & all interactions
Keep checking

Other Drugs & Niacin

Browse every other medication we’ve checked against Niacin — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
726Moderate
0Minor
2,103No known interaction
726 Moderate 2,103 No interaction
Moderate

726 interactions

Showing 60 of 726 moderate interactions — see all 726 on the Niacin page.

No interaction 2,103 drugs checked — show the list

We also checked Niacin against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,103 medications checked with no known interaction — see the full Niacin list.

See the full Niacin interactions page
See every supplement checked against Metformin, Rosiglitazone, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Niacin monograph › Uses, safety, and every drug interaction in one place Metformin, Rosiglitazone supplement interactions › Every supplement checked against Metformin, Rosiglitazone, ranked by severity Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Niacin and Metformin, Rosiglitazone Together: Common Questions

Can you take Niacin with Metformin, Rosiglitazone?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Niacin and Metformin, Rosiglitazone?
Metformin, Rosiglitazone belongs to more than one drug category, and Niacin interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Niacin and Metformin, Rosiglitazone interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.