Trimethoprim and Metformin Interaction
Drug interaction information between Trimethoprim and Metformin.
Trimethoprim and Metformin have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Trimethoprim and Metformin. This page displays the available source-record category and label text. The category is not an individual risk estimate or medication-combination direction.
How They Interact
Trimethoprim can stop your kidneys from clearing metformin out of your body as fast as they should.
FDA Label Information
Sulfamethoxazole and trimethoprim potentiates the effect of oral hypoglycemics that are metabolized by CYP2C8 (e.g., pioglitazone, repaglinide, and rosiglitazone) or CYP2C9 (e.g., glipizide and glyburide) or eliminated renally via OCT2 (e.g., metformin). Cases of interactions with other OCT2 substrates, memantine and metformin, have also been reported.
Trimethoprim Also Interacts With
- Theophylline major
- Prenatal Multivitamin moderate
- Spironolactone moderate
- Spironolactone (Acne) moderate
- Glipizide minor
Metformin Also Interacts With
- Bictegravir/Emtricitabine/Tenofovir moderate
- Dolutegravir/Lamivudine moderate
- Empagliflozin moderate
- Empagliflozin/Linagliptin moderate
- Ertugliflozin moderate
Frequently Asked Questions
What SPL severity band is on file for Trimethoprim + Metformin?
Compiled FDA labeling labels this pair minor. That is a source-record field, not an individual medication-combination decision.
Which drug in this pair has the larger labeled-interaction portfolio?
Metformin has 27 labeled pairs on file vs Trimethoprim's 22. In the minor band specifically: Trimethoprim has 18 (also Glipizide, Warfarin, Methotrexate, Pioglitazone); Metformin has 17 (also Topiramate, Dolutegravir, Ranolazine, Cimetidine).
What mechanism field is on file for Trimethoprim and Metformin?
Trimethoprim can stop your kidneys from clearing metformin out of your body as fast as they should.
Trimethoprim carries more major-labeled pairs than Metformin
SPL source-record counts only. This page's band is minor · classes on file: Trimethoprim (Dihydrofolate Reductase Inhibitor); Metformin (Biguanide).
Trimethoprim has 1 major-labeled pair vs Metformin's 0. This page itself is in the minor band, not the major band.
1 major · 3 moderate · 18 minor · 22 total
- Other minor peers for Trimethoprim
- Glipizide
- Warfarin
- Methotrexate
- Pioglitazone
0 major · 10 moderate · 17 minor · 27 total
- Other minor peers for Metformin
- Topiramate
- Dolutegravir
- Ranolazine
- Cimetidine
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. This registry does not provide individual medication-combination directions.
Read our methodology - how this data is sourced, computed, and verified.