I showed my Dr. a bottle of Testrogel(tm) and told him that it was good stuff but I wanted to try the perscription version which contains testosterone. He wrote me a scrip for a years worth of androderm patches, but they are weak, takes like 6 a day to get enough test. (I have used them like prop at the end of a cycle, when these are gone I won't buy any more)
I doubt you would get anything injectible. Docs usually will administer injectible test, you have to go into the office to get it and they can charge more since it's an office visit for each treatment.