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Zepbound ® (tirzepatide) injection
2.5 mg/ 5 mg/ 7.5 mg/ 10 mg/ 12.5 mg/ 15 mg
This information is provided in response to your request. Resources may contain information about doses, uses, formulations and populations different from product labeling. See Prescribing Information above, if applicable.
Can people take Zepbound® (tirzepatide) with levothyroxine?
Levothyroxine is not contraindicated with the use of tirzepatide; however, tirzepatide delays gastric emptying and thereby has the potential to impact the absorption of concomitantly administered oral medications like levothyroxine.
See important safety information, including boxed warning, in the attached prescribing information.
Use With Levothyroxine
Levothyroxine is not contraindicated with the use of tirzepatide.1
Tirzepatide delays gastric emptying and thereby has the potential to impact the absorption of concomitantly administered oral medications. Caution should be exercised when oral medications are concomitantly administered with tirzepatide.1
The impact of tirzepatide on gastric emptying was greatest after a single dose of 5 mg and diminished after subsequent doses.1
Monitor patients on oral medications dependent on threshold concentrations for efficacy and those with a narrow therapeutic index (NTI) when concomitantly administered with tirzepatide.1
The Food and Drug Administration (FDA) has concluded that levothyroxine is a NTI drug.2
The prescribing information for levothyroxine includes a warning for worsening of diabetic control: Addition of levothyroxine therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements. Carefully monitor glycemic control after starting, changing, or discontinuing levothyroxine.3
Eli Lilly and company does not provide specific treatment recommendations. We strongly encourage patients to go to their healthcare provider for treatment advice because they know their patient's medical history the best.
Lilly cannot provide a recommendation on use of tirzepatide in a patient taking levothyroxine because while these patients were not excluded from clinical studies; there was no specific subanalyses performed on this patient population. There were no specific recommendations for additional dose adjustments or monitoring for these patients. Investigators were instructed to use their discretion.
The healthcare practitioner may use the information provided, the patient’s prior medical history and concomitant medications, and other individual factors in developing a treatment plan. The healthcare practitioner should consider potential risks and benefits of treatment options and monitor appropriately.
No information about changes in thyroid hormones (endogenous or exogenous) is included in the current US Mounjaro (tirzepatide) prescribing information.1 At the time of review, to the extent there was data available on changes in thyroid hormones from the tirzepatide clinical trials and postmarketing experience, it did not meet FDA's criteria for clinical significance, causality to the drug, or relevance to patient safety and treatment decisions.4
Patient safety is Eli Lilly and Company’s top priority and we actively engage in evaluating, monitoring, and reporting safety information for all our medicines. If new information indicates a new safety concern or signal for the product or the class, including postmarketing experience, the prescribing information will be properly updated in alignment with regulatory authorities.4
Enclosed Prescribing Information
ZEPBOUND® (tirzepatide) injection, for subcutaneous use, Lilly
1. Zepbound [package insert]. Indianapolis, IN: Eli Lilly and Company; 2026.
2. US Food and Drug Administration (FDA). Draft Guidance on Levothyroxine Sodium. Updated December 2014. Accessed June 29, 2026. https://www.accessdata.fda.gov/drugsatfda_docs/psg/Levothyroxine%20sodium_draft_Oral%20tab_RLD%20021116%20%20%20%20%20%20%20%20%20%20%20%20%20%20021210%20%20%20%20%20%20%20%20%20%20%20%20%20%20021301%20%20%20%20%20%20%20%20%20%20%20%20%20%20021342%20%20%20%20%20%20%20%20%20%20%20%20%20%20021402_RC12-14.pdf
3. Synthroid [package insert]. North Chicago, IL: AbbVie Inc; 2024.
4. US Food and Drug Administration. Frequently asked questions about labeling for prescription medicines for healthcare professionals. Updated April 1, 2024. Accessed June 30, 2026. https://www.fda.gov/drugs/fdas-labeling-resources-human-prescription-drugs/frequently-asked-questions-about-labeling-prescription-medicines
Date of Last Review: June 24, 2026