Levothyroxine and Carbamazepine Interaction
Drug interaction information between Levothyroxine and Carbamazepine.
Levothyroxine and Carbamazepine have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Levothyroxine and Carbamazepine. 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
Carbamazepine changes how thyroid hormone travels in your blood, which can lower the levels of hormone found in medical tests.
FDA Label Information
Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total and free T4 may be reduced by 20% to 40%, but most patients have normal serum TSH levels and are clinically euthyroid. Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement.
Levothyroxine Also Interacts With
- Sertraline minor
- Furosemide minor
- Propranolol minor
- Ferrous Sulfate minor
- Amitriptyline minor
Carbamazepine Also Interacts With
- Nirmatrelvir/Ritonavir major
- Ranolazine major
- Risperidone major
- Lithium moderate
- Apixaban moderate
Frequently Asked Questions
What SPL severity band is on file for Levothyroxine + Carbamazepine?
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?
Carbamazepine has 129 labeled pairs on file vs Levothyroxine's 22. In the minor band specifically: Levothyroxine has 22 (also Sertraline, Furosemide, Propranolol, Ferrous Sulfate); Carbamazepine has 110 (also Omeprazole, Ibuprofen, Citalopram, Amitriptyline).
What mechanism field is on file for Levothyroxine and Carbamazepine?
Carbamazepine changes how thyroid hormone travels in your blood, which can lower the levels of hormone found in medical tests.
Carbamazepine carries more major-labeled pairs than Levothyroxine
SPL source-record counts only. This page's band is minor · classes on file: Levothyroxine (Thyroid Hormone); Carbamazepine (Anticonvulsant).
Carbamazepine has 3 major-labeled pairs vs Levothyroxine's 0. This page itself is in the minor band, not the major band.
0 major · 0 moderate · 22 minor · 22 total
- Other minor peers for Levothyroxine
- Sertraline
- Furosemide
- Propranolol
- Ferrous Sulfate
3 major · 16 moderate · 110 minor · 129 total
- Other minor peers for Carbamazepine
- Omeprazole
- Ibuprofen
- Citalopram
- Amitriptyline
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.