ABSTRACT
Background@#Levothyroxine is an essential drug for the treatment of hypothyroidism or related diseases. Several studies have reported an association between the effects of levothyroxine treatment and time of administration, which can be inconsistent. @*Objective@#This study was conducted to compare the levels of thyroid-stimulating hormone or free thyroxine between morning and nighttime dosing of levothyroxine. @*Methods@#We reviewed previously reported relevant articles and conducted a meta-analysis. @*Results@#In total, five studies were included in this meta-analysis. Results showed that thyroid-stimulating hormone (standard difference in means [SE]=0.321; 95% confidence interval [CI], -0.016 to 0.657) and free thyroxine (SE= −1.367; 95% CI, -2.943 to 0.210) levels did not differ significantly between morning (before breakfast) and nighttime (before bedtime) administration. @*Conclusion@#This is the first meta-analysis to evaluate the effects of time of administration on levothyroxine levels in patients with hypothyroidism. Based on our results, we suggest considering patients’ lifestyles or daily routines when counselling them on the optimal time of administration for levothyroxine.