Levothyroxine and Propranolol Interaction
Drug interaction information between Levothyroxine and Propranolol.
Levothyroxine and Propranolol have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Levothyroxine and Propranolol. 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
Taking large doses of this blood pressure medicine can change the levels of thyroid hormones in your blood. However, it usually does not change how your thyroid actually functions or how you feel.
What To Do
Your doctor may monitor your thyroid blood tests if you take high doses of propranolol. Usually, no change in your thyroid medication is needed.
FDA Label Information
Drug or Drug Class Effect Beta-adrenergic antagonists (e.g., Propranolol > 160 mg/day) In patients treated with large doses of propranolol (> 160 mg/day), T3 and T4 levels change, TSH levels remain normal, and patients are clinically euthyroid. Drug or Drug Class Effect Beta-adrenergic antagonists (e.g., Propranolol > 160 mg/day) In patients treated with large doses of propranolol (> 160 mg/day), T3 and T4 levels change, TSH levels remain normal, and patients are clinically euthyroid.
Levothyroxine Also Interacts With
- Sertraline minor
- Furosemide minor
- Ferrous Sulfate minor
- Amitriptyline minor
- Carbamazepine minor
Frequently Asked Questions
Can I take Levothyroxine and Propranolol together?
This is a minor interaction. Your doctor may monitor your thyroid blood tests if you take high doses of propranolol. Usually, no change in your thyroid medication is needed.
How serious is the interaction between Levothyroxine and Propranolol?
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 Levothyroxine and Propranolol interact?
Taking large doses of this blood pressure medicine can change the levels of thyroid hormones in your blood. However, it usually does not change how your thyroid actually functions or how you feel.
Understanding the Levothyroxine and Propranolol Interaction
FDA-approved prescribing information for these two drugs flags their combination as a minor-severity interaction. Levothyroxine belongs to the Thyroid Hormone class and Propranolol belongs to the Non-Selective Beta-Blocker class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Taking large doses of this blood pressure medicine can change the levels of thyroid hormones in your blood. 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. Levothyroxine has 22 total documented interactions on file in this dataset, and Propranolol has 44. 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 monitor your thyroid blood tests if you take high doses of propranolol. 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 Levothyroxine or Propranolol 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.