Drug interactions
Chlorothiazide + Metformin
Severity: Minor
Chlorothiazide and Metformin: minor interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Thiazide diuretics can raise blood glucose and impair glucose tolerance, which may reduce the effectiveness of metformin. The effect is more evident at higher doses.
What this interaction means in plain words
Chlorothiazide and Metformin have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Chlorothiazide belongs to Cardiovascular; Metformin belongs to Endocrine.
Why it happens
Thiazide-induced hypokalemia and reduced insulin secretion and sensitivity oppose metformin's glucose-lowering effect.
What to do
Monitor blood glucose when starting or increasing the thiazide. Adjust the metformin dose if control worsens.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Metformin
Other interactions of Chlorothiazide
Frequently asked questions
Can I take Chlorothiazide with Metformin?
MediHelp rates the interaction as minor. Chlorothiazide and Metformin have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Thiazide diuretics can raise blood glucose and impair glucose tolerance, which may reduce the effectiveness of metformin. The effect is more evident at higher doses.
How serious is the interaction between Chlorothiazide and Metformin?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor blood glucose when starting or increasing the thiazide. Adjust the metformin dose if control worsens.
What other medicines interact with Metformin?
MediHelp also lists interactions of Metformin with, for example, Contrast media, Diatrizoate meglumine / diatrizoate, Diatrizoate. The full list is on the Metformin page.
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