Drug & supplement interaction

Niacin + Glipizide

Glipizide brand names: Glucotrol, Glucotrol XL.

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

Niacin has a moderate interaction with Glipizide. Niacin can increase blood glucose levels and may diminish the effects of antidiabetes drugs.

Read the full interaction report
SeverityModerate
LikelihoodProbable
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Niacin and Glipizide

Here is the interaction we found between these two, with the evidence behind it.

Moderate

ANTIDIABETES DRUGS

Why this applies to Glipizide

Glipizide falls under ANTIDIABETES DRUGS — the group Niacin interacts with.

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 know if you take glipizide for type 2 diabetes and are thinking about a niacin supplement. Glipizide works by nudging your pancreas to release more insulin, which brings your blood sugar down. Niacin can push in the opposite direction. At higher, drug-like doses it tends to make your body more resistant to insulin and bump up the sugar your liver makes, so your blood sugar can creep higher than usual.

In plain terms, niacin may partly cancel out what glipizide is doing, meaning your numbers could run high. This mostly shows up at large doses (around 1.5 grams a day or more). Everyday vitamin amounts usually aren't a problem. If you start high-dose niacin, talk with your pharmacist or doctor first, since some folks need their diabetes medicine adjusted.

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 Glipizide one above is one of them. If you take anything else, check it against the full list below.

Moderate 726 No known interaction 2,104 (incl. Glipizide)
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.

From our Q&A

Questions About Niacin or Glipizide

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Niacin or Glipizide, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Glipizide

This page covers Niacin only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Glipizide page lists 307 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Siberian Cocklebur (major), Acai (moderate), Adrafinil (moderate) and African Wild Potato (moderate).

By severity: 2 major · 256 moderate · 49 minor.

From our pharmacist’s overview on the Glipizide page

“Glipizide (Glucotrol, Glucotrol XL) lowers blood sugar by prompting the pancreas to release more insulin, and that same power is why I read its supplement list with real seriousness. Of the 307 ingredients on file, 239 also act on blood glucose, so stacking them can drive sugar dangerously low.”

Reviewed by 2 · Jul 18, 2026

Open the Glipizide 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 Glipizide 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 Glipizide 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%

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

29 days ago today
Medication Glipizide
Top half

#1,029 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
Medication

About Glipizide

What Is Glipizide Used For?

Brand names: Glucotrol, Glucotrol XL

Glipizide tablets and glipizide extended-release tablets are both used as an add-on to diet and exercise to improve blood sugar (glucose) control in adults with type 2 diabetes. It is not used for type 1 diabetes or diabetic ketoacidosis (a serious complication of uncontrolled blood sugar).

See full Glipizide drug information
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 Glipizide, 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 Glipizide supplement interactions › Every supplement checked against Glipizide, ranked by severity Glipizide drug information › The full plain-English guide to this medication 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 Glipizide Together: Common Questions

Can you take Niacin with Glipizide?
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.
How serious is the Niacin and Glipizide 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

Still Have a Question About Glipizide and Niacin?

Our pharmacists answer your medication & supplement questions — free.

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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.