Fasting vs Nonfasting, Dose-adjusted Levothyroxine Ingestion in Hypothyroidism: A Randomized Clinical Trial
Errata to this article were published (J Clin Endocrinol Metab, 17 Mar 2026 ↗ · 17 Jun 2026 ↗)
Authors' conclusion
LT4 ingestion with breakfast with a 15% dose increase maintained TSH stability and improved patient well-being. Given the strong patient preference, this patient-centered approach may offer a viable alternative to fasting administration.
Study context
- Population
- Adults with well-controlled hypothyroidism; 80.7% female, median age 62y (IQR 49–69)
- Participants
- 88 adults
- Comparison
- Dose-adjusted levothyroxine (LT4) with breakfast vs fasting LT4 intake
- Breakfastn = 45
- Fastingn = 43reference
- Primary endpoint
- TSH stability: 2 consecutive values within reference range and maximum ±1 mIU/L change from baseline
- Follow-up
- Followed until stability, maximum 24 weeks
Methodological detailscrossover of fasting group to nonfasting intake after initial period
- Crossover of fasting group to nonfasting intake after initial period
Primary result
As reported in the abstract
TSH stability
P = not significant
Further findings
Improvement in self-reported well-being
P = 0.07
Preference for nonfasting intake
P < 0.001
TSH stability in crossover group
- Similar findings observed in the crossover group
Chose to continue nonfasting intake · end of study
- Chose to continue nonfasting intake
- 88.9%
Original publication
Fasting vs Nonfasting, Dose-adjusted Levothyroxine Ingestion in Hypothyroidism: A Randomized Clinical Trial. J Clin Endocrinol Metab. Published 23 December 2025. doi:10.
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