Drug interactions
Calcium carbonate + Levothyroxine
Severity: Moderate
Calcium carbonate and Levothyroxine: moderate 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
Calcium carbonate binds levothyroxine and lowers its absorption, which can raise TSH and cause hypothyroid symptoms.
What this interaction means in plain words
Calcium carbonate and Levothyroxine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Calcium carbonate belongs to Gastrointestinal Tract; Levothyroxine belongs to Endocrine.
Why it happens
Levothyroxine adsorbs to calcium carbonate and its dissolution is impaired by higher gastric pH, so absorption falls.
What to do
Separate administration by at least 4 hours and check TSH 6 to 8 weeks after starting or changing calcium.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Calcium carbonate and Levothyroxine, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 14 days on the web. No card needed.
Other interactions of Calcium carbonate
Other interactions of Levothyroxine
Frequently asked questions
Can I take Calcium carbonate with Levothyroxine?
MediHelp rates the interaction as moderate. Calcium carbonate and Levothyroxine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Calcium carbonate binds levothyroxine and lowers its absorption, which can raise TSH and cause hypothyroid symptoms.
How serious is the interaction between Calcium carbonate and Levothyroxine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Separate administration by at least 4 hours and check TSH 6 to 8 weeks after starting or changing calcium.
What other medicines interact with Calcium carbonate?
MediHelp also lists interactions of Calcium carbonate with, for example, Acalabrutinib, Alendronate, Amlodipine-hydrochlorothiazide-valsartan. The full list is on the Calcium carbonate page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
