Olmesartan and Hydrochlorothiazide Interaction
Drug interaction information between Olmesartan and Hydrochlorothiazide.
Olmesartan and Hydrochlorothiazide have a documented moderate interaction in FDA labeling.
FDA drug labeling documents a moderate-severity interaction between Olmesartan and Hydrochlorothiazide. 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
Both drugs work to lower blood pressure, which can increase the risk of your blood pressure dropping too low or your kidney function changing.
What To Do
Your doctor should monitor your blood pressure and kidney health regularly while you are taking this combination.
FDA Label Information
7 DRUG INTERACTIONS Lithium: Risk of lithium toxicity ( 7.2 ) Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): Reduced diuretic, natriuretic and antihypotensive effects; increased risk of renal toxicity ( 7.3 ) Dual inhibition of the renin-angiotensin system: Increased risk of renal impairment, hypotension, and hyperkalemia ( 7.4 ) Colesevelam hydrochloride: Consider administering olmesartan at least 4 hours before colesevelam hydrochloride dose ( 7.5 ) Antidiabetic drugs: Dosage adjustment may be required ( 7.6 ) Cholestyramine and colestipol: Reduced absorption of thiazides ( 7.6 ) 7.1...
Olmesartan Also Interacts With
- Aliskiren major
- Lithium moderate
- Colesevelam moderate
- Cholestyramine moderate
- Colestipol moderate
Hydrochlorothiazide Also Interacts With
- Aliskiren major
- Hydrochlorothiazide/Triamterene major
- Lisinopril major
- Losartan minor
- Spironolactone minor
Frequently Asked Questions
Can I take Olmesartan and Hydrochlorothiazide together?
This is a moderate interaction. Your doctor should monitor your blood pressure and kidney health regularly while you are taking this combination.
How serious is the interaction between Olmesartan and Hydrochlorothiazide?
This interaction is classified as "moderate" severity by the FDA. Moderate interactions may worsen your condition or change how your medications work.
Why do Olmesartan and Hydrochlorothiazide interact?
Both drugs work to lower blood pressure, which can increase the risk of your blood pressure dropping too low or your kidney function changing.
Understanding the Olmesartan and Hydrochlorothiazide Interaction
FDA-approved prescribing information for these two drugs flags their combination as a moderate-severity interaction. Olmesartan belongs to the Angiotensin II Receptor Blocker (ARB) class and Hydrochlorothiazide belongs to the Thiazide Diuretic class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Both drugs work to lower blood pressure, which can increase the risk of your blood pressure dropping too low or your kidney function changing. 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. Olmesartan has 7 total documented interactions on file in this dataset, and Hydrochlorothiazide has 31. 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 should monitor your blood pressure and kidney health regularly while you are taking this combination. 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 Olmesartan or Hydrochlorothiazide 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.