Ferrous Sulfate and Levothyroxine Interaction
Drug interaction information between Ferrous Sulfate and Levothyroxine.
Ferrous Sulfate and Levothyroxine have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Ferrous Sulfate and Levothyroxine. 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
Ferrous sulfate can stick to levothyroxine in your stomach, which prevents your body from absorbing the thyroid medicine correctly.
FDA Label Information
Drug or Drug Class Effect Phosphate Binders (e.g., calcium carbonate, ferrous sulfate, sevelamer, lanthanum) Phosphate binders may bind to levothyroxine. Drug or Drug Class Effect Phosphate Binders (e.g., calcium carbonate, ferrous sulfate, sevelamer, lanthanum) Phosphate binders may bind to levothyroxine.
Levothyroxine Also Interacts With
- Sertraline minor
- Furosemide minor
- Propranolol minor
- Amitriptyline minor
- Carbamazepine minor
Frequently Asked Questions
What SPL severity band is on file for Ferrous Sulfate + Levothyroxine?
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?
Levothyroxine has 22 labeled pairs on file vs Ferrous Sulfate's 2. In the minor band specifically: Ferrous Sulfate has 1; Levothyroxine has 22 (also Sertraline, Furosemide, Propranolol, Amitriptyline).
What mechanism field is on file for Ferrous Sulfate and Levothyroxine?
Ferrous sulfate can stick to levothyroxine in your stomach, which prevents your body from absorbing the thyroid medicine correctly.
Levothyroxine's labeled portfolio outnumbers Ferrous Sulfate
SPL source-record counts only. This page's band is minor · classes on file: Ferrous Sulfate (Iron Supplement); Levothyroxine (Thyroid Hormone).
0 major · 1 moderate · 1 minor · 2 total
Ferrous Sulfate has no other minor-band peer in this dataset besides Levothyroxine.
0 major · 0 moderate · 22 minor · 22 total
- Other minor peers for Levothyroxine
- Sertraline
- Furosemide
- Propranolol
- 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.