Or better yet, just be honest with him. If I see a patient who is muscular and he requests LFT's, I suspect steroid use unless he has a history of hep C or some other reason. Personally, I think someone who is honest about their reasoning and requests LFT's is health conscious and is doing the smart thing.
Ideally, you should check your LFT's both before and after steroid use (for a baseline comparison). Even more ideal, a doc should be able to prescribe them to you to monitor for side effects.
This is a personal beef of mine (no pun intended). I think there were less complications from steroid use when physicians were able to prescribe them. Since they are on the underground market now, too many people have developed severe, severe side effects from fake products, unsterile packaging, not following lab tests closely, etc.
Just a word of advice: Also have your cholesterol checked when you have your LFT's checked. Anabolic steroids can lower your HDL (good cholesterol) and raise your LDL (bad cholesterol) to astronomical numbers!