Candbear,

If it were me, I wouldn't tell. I would keep it to myself as long as I could. I doubt it would benefit you at all if you told and it may make them start really watching you as they may feel they won't be able to totally trust you.
It's sad, but most employers don't really care about their employees health. All they care about is that you get the job done.
Try and hold out until you can see your pdoc or try and start taking your meds as soon as possible.
I do hope everything will turn out OK for you.
Take care,
Linda