Glipizide and Phenytoin Interaction
Drug interaction information between Glipizide and Phenytoin.
Glipizide and Phenytoin have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Glipizide and Phenytoin. Major interactions are generally avoided, moderate ones may need monitoring or a dose adjustment, and minor ones are usually low-risk. This page shows the documented mechanism and guidance. Label-documented interactions are not a complete safety review, so always confirm your own medications with a pharmacist or doctor. Educational information, not medical advice.
How They Interact
Phenytoin can interfere with how glipizide controls blood sugar, potentially causing your blood sugar levels to rise.
What To Do
Your doctor may need to monitor your blood sugar more closely and adjust your medication dose if necessary.
FDA Label Information
These drugs include the thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs, and isoniazid.
Glipizide Also Interacts With
- Fluconazole minor
- Colesevelam minor
- Probenecid minor
- Lovastatin minor
- Posaconazole minor
Phenytoin Also Interacts With
- Nirmatrelvir/Ritonavir major
- Posaconazole major
- Ranolazine major
- Voriconazole major
- Apixaban moderate
Frequently Asked Questions
Can I take Glipizide and Phenytoin together?
This is a minor interaction. Your doctor may need to monitor your blood sugar more closely and adjust your medication dose if necessary.
How serious is the interaction between Glipizide and Phenytoin?
This interaction is classified as "minor" severity by the FDA. Minor interactions are unlikely to cause significant problems but should still be mentioned to your healthcare provider.
Why do Glipizide and Phenytoin interact?
Phenytoin can interfere with how glipizide controls blood sugar, potentially causing your blood sugar levels to rise.
Understanding the Glipizide and Phenytoin Interaction
FDA-approved prescribing information for these two drugs flags their combination as a minor-severity interaction. Glipizide belongs to the Sulfonylurea class and Phenytoin belongs to the Anticonvulsant (Hydantoin) class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Phenytoin can interfere with how glipizide controls blood sugar, potentially causing your blood sugar levels to rise. Severity tiers matter: major flags generally advise avoidance, moderate flags often require monitoring or dose adjustment, and minor flags may only call for awareness.
Context around a specific patient determines real-world impact. Glipizide has 8 total documented interactions on file in this dataset, and Phenytoin has 147. Each additional medication compounds the interaction surface, which is why pharmacists run full-profile checks rather than evaluating one pair at a time. FDA-derived guidance for this pair is: Your doctor may need to monitor your blood sugar more closely and adjust your medication dose if necessary. Timing of doses, renal and hepatic function, age, and other concurrent prescriptions all shape whether a labeled interaction matters clinically.
An interaction flag is not a verdict. A large share of labeled interactions are managed routinely in clinical practice, the fix may be as simple as spacing doses or adding a monitoring test. Others require the prescriber to choose a different medication entirely. This page surfaces FDA-sourced labeling and openFDA data for educational purposes only; it is not medical advice and cannot account for your full clinical picture. Never start, stop, or adjust either Glipizide or Phenytoin based on a web page, speak with your prescriber or pharmacist before making any change.
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. Always consult your healthcare provider about drug interactions.
Read our methodology - how this data is sourced, computed, and verified.