No, no, no, etc. BUT . . .
Routine blood tests do not pick up AS use.
BUT: Routine blood tests can give an indication that someone [/i]might[/i] be on AS. Specifically, some roids can elevate the hematocrit, hemoglobin, prostate specific antigen, and other lab work. Also, some roids can cause edema (water retention), so indications of edema in a person without any clinical reason (such as congestive heart failure or poor circulation from diabetes) could be an indication of AS use.
As for the doctor blabbing, can't happen - your communications with your physician are protected by doctor-patient confidentiality.
With all that said, I would be up front with your doctor about any AS use, since it could have an effect on your overall health. However, ask your doctor not to comment on your AS use in your medical chart since it could become an issue in the event that your chart were subpoenaed for a civil lawsuit (such as from an accident, whether you are the plaintiff or the defendant) down the road.
That will be five cents, please . . .