Health issues in grad school - how many extensions are acceptable?
I would have some general conversation with the department, and with health services versus these atomistic requests for extra time on specific projects.  
If the situation is chronic, perhaps you need to defer your studies as you are routinely unable to keep up.  But that depends on the specifics: frequency and duration of your issues, are they predictable (e.g. chemo timing) or random.  Likelihood to improve.  And of course if the situation is a genuine medical impairment or if you are struggling with content and using it as an excuse (not an accusation, just within the theoretical solution space).


P.s.  If the course is not part of the requirements, I would just drop it.  Seems like obvious way to handle the impairment.  You can still get your program done.  Just not with extra volume.