J Clin Endocrinol Metab

Do patients really need to fast before taking levothyroxine?

February 12, 2026

A randomized trial of 88 adults (80.7% female; median age, 62 years) with well-controlled hypothyroidism compared traditional fasting levothyroxine intake vs. taking the medication at breakfast using a 15% dose increase. TSH stability was achieved in 74.4% of the fasting group and 73.3% of the breakfast group, with comparable mean TSH changes (0.27 vs. 0.29 mIU/L). Patients taking levothyroxine with breakfast reported greater improvements in well-being (33.3% vs. 16.3%) and stronger preference for nonfasting intake (76.2% vs. 44.2%). No adverse events were reported.

Clinical takeaway: Taking levothyroxine with breakfast using a 15% dose increase may maintain thyroid control while improving adherence and quality of life.

Source:

Willems JIA, et al. (2025, December 23). J Clin Endocrinol Metab. Fasting vs. Non-Fasting, Dose-Adjusted Levothyroxine Ingestion In Hypothyroidism: A Randomized Clinical Trial. https://pubmed.ncbi.nlm.nih.gov/41431302/