I don't mean to sound dismissive as you do raise a good point, but I'd like to think that if someone is hypoglycemic they'd be fully aware of it by the time they're old enough to be dabbling in illicit psychoactive substances.
I personally won't so much advise someone to fast in the same fashion I choose to, but will suggest abstaining from eating anything for a few hours prior to taking their MDMA.
PERSONALLY as someone not dealing with any medical conditions regarding blood glucose levels, I choose to fast the entire day I plan to roll. I'd like to think nobody would blindly follow that kind of practice without at least some thought, particularly if they know they're hypoglycemic or feel excessively exhausted part way through fasting.
For the sake of full info: my practice is consuming absolute minimal caloric intake from when I go to bed the night prior to rolling (pretty much only BCAAs, so maybe 50cal for the day?) until the morning after rolling, totally "36 hours" or so fasted. The day I planned to roll, I used to commit to a decent pushbike ride into the city and back which was about 700-800cal.