You should wait and give as little info as possible. The thing is, it is very hard to prove they fired you for medical leave. I didn't mean to, but I got pregnant the day I got a promotion. Let them know right away. Went on maternity leave. Nothing was ever the same. They made up reasons to fire me.... they waited just long enough to make it look like that's not why they're firing me. Right after Christmas, pink slip. Up to this point I was the subject matter expert, best metrics in the division, never late, got along with people...