How long before the shrink medicates me?

I know it's different for everyone, but a general time frame...How long does someone have to have therapy before you can get meds? I am dx ADHD and changing from my family doctor to a psychologist and someone in his office can write RXs. Will they have to test me or something? Maybe my diagnosis from the family doctor is enough? Any ideas? I'm nervous and I don't really kow what to expect. I am new to therapy, though I has had this diagnosis and medication for quite some time.