No, it actually helps me sleep through the night as it seems to control the kind of adrenaline hot flashes that @sierrawoods originally posted about. I checked with my pharmacist, and she said it can be taken at night. I just need to make sure it is at least 2 hours after I’ve had anything to eat (so it prevents snacking in the evening too!) Luckily, I have the kind of work schedule that allows me to have an early dinner to accommodate taking my Synthroid on as empty a stomach as possible before I go to bed 🙂