Metformin and Trimethoprim Sulfamethoxazole: Drug Interaction Guide

Quick answer: This combination requires caution. Metformin and Trimethoprim Sulfamethoxazole can be used together with adjustments and monitoring.

Interaction severity: Moderate — caution required

How Metformin interacts with Trimethoprim Sulfamethoxazole

Trimethoprim inhibits OCT2 and MATE renal transporters that excrete metformin, increasing metformin exposure and lactic acidosis risk; sulfamethoxazole independently potentiates hypoglycaemia.

What you should do

Monitor blood glucose closely; consider holding metformin during short courses or if eGFR <45 mL/min/1.73 m².

Key facts

Severity

Moderate — caution required

Mechanism

Trimethoprim inhibits OCT2 and MATE renal transporters that excrete metformin, increasing metformin exposure and lactic ...

Action

Monitor blood glucose closely; consider holding metformin during short courses or if eGFR <45 mL/min/1.73 m².

Important medical disclaimer: This page provides educational information about drug interactions for general reference. It is not a substitute for professional medical advice, diagnosis, or treatment. Always discuss your specific medications with a qualified healthcare provider before starting, stopping, or changing any treatment. About our editorial team.

Frequently asked questions

Can I take Metformin and Trimethoprim Sulfamethoxazole together?

With caution. Monitor blood glucose closely; consider holding metformin during short courses or if eGFR <45 mL/min/1.73 m².

What is the severity of this interaction?

The interaction between Metformin and Trimethoprim Sulfamethoxazole is classified as Moderate — caution required. Trimethoprim inhibits OCT2 and MATE renal transporters that excrete metformin, increasing metformin exposure and lactic acidosis risk; sulfamethoxazole independently potentiates hypoglycaemia.

What should I do if I'm prescribed both?

Monitor blood glucose closely; consider holding metformin during short courses or if eGFR <45 mL/min/1.73 m². Always consult your prescribing clinician — do not stop or change medications without medical guidance.

Last reviewed: by iMedic Medical Editorial Team. Our editorial process.