Home/ Interactions/ Calcium × Levothyroxine

Calcium × Levothyroxine

MODERATE Well-Established Evidence

Mechanism

Calcium forms insoluble complexes with levothyroxine, reducing absorption.

Effect

Reduced levothyroxine absorption; hypothyroid symptoms

Management

Separate doses by at least 4 hours. Take levothyroxine on empty stomach.

Plain Language Summary

✨ AI-generated · Qwen 3.6 · grounded in 2 sources · methodology

This interaction is considered moderate because calcium can interfere with how much levothyroxine your body absorbs. This reduction in absorption may lead to symptoms of an underactive thyroid. The data suggests separating these doses by at least four hours.

Source

Singh N et al. JAMA 2000; FDA levothyroxine labeling

Research

Supporting Research

First-line drugs for hypertension
PMID:29667175 DOI 2018
Beta-blockers for hypertension
PMID:28107561 DOI 2017
Calcium channel blockers versus other classes of drugs for hypertension
PMID:34657281 DOI 2021
Effect of early treatment with anti-hypertensive drugs on short and long-term mortality in patients with an acute cardiovascular event
PMID:19821384 DOI 2009
Phlebotonics for venous insufficiency
PMID:27048768 DOI 2016
Calcium channel blockers versus other classes of drugs for hypertension
PMID:35000192 DOI 2022
Calcium supplementation for prevention of primary hypertension
PMID:34693985 DOI 2021
Calcium supplementation for prevention of primary hypertension
PMID:35014026 DOI 2022
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Medical Disclaimer: This interaction record is for informational and educational purposes only and does not constitute medical advice. Always consult your healthcare provider or pharmacist before combining any supplement with prescription medications.