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Iodine × Levothyroxine

MODERATE INTERACTION — Well-Established Evidence

⚠️ Mechanism

Excess iodine can paradoxically inhibit thyroid hormone synthesis (Wolff-Chaikoff effect) and interfere with thyroid medication.

📋 Effect

Altered thyroid function; hypothyroidism in susceptible individuals

💊 Management

Avoid high-dose iodine supplements (>1mg/day) with thyroid disease. Monitor TSH.

Plain Language Summary

Taking high doses of iodine while on levothyroxine can be problematic for your thyroid health. Excess iodine can interfere with how your medication works and may cause your thyroid to become underactive.

Source

Leung AM, Braverman LE. Thyroid 2012

Supporting Research

Umbilical cord antiseptics for preventing sepsis and death among newborns PMID:41881430 DOI:10.1002/14651858.CD008635.pub3 2026
Interventions for cutaneous molluscum contagiosum PMID:28513067 DOI:10.1002/14651858.CD004767.pub4 2017
Chlorhexidine vs Povidone-Iodine and Incidence of Catheter-Related Infections: A Systematic Review and Meta-Analysis PMID:41678192 DOI:10.1001/jamanetworkopen.2025.58954 2026
Radioiodine Remnant Ablation for Differentiated Thyroid Cancer: A Systematic Review and Meta-analysis PMID:33792650 DOI:10.1001/jamaoto.2021.0288 2021
Alcoholic chlorhexidine skin preparation or triclosan-coated sutures to reduce surgical site infection: a systematic review and meta-analysis of high-quality randomised controlled trials PMID:35644158 DOI:10.1016/S1473-3099(22)00133-5 2022
Oral hygiene care for critically ill patients to prevent ventilator-associated pneumonia PMID:23939759 DOI:10.1002/14651858.CD008367.pub2 2013
Interventions for ingrowing toenails PMID:22513901 DOI:10.1002/14651858.CD001541.pub3 2012
Interventions for the management of malignant pleural effusions: a network meta-analysis PMID:27155783 DOI:10.1002/14651858.CD010529.pub2 2016
Medical Disclaimer: This interaction record is for informational and educational purposes only and does not constitute medical advice. Drug-supplement interactions can be dangerous. Always consult your healthcare provider or pharmacist before combining any supplement with prescription medications. Do not stop or change any medication without professional guidance.