best approach i think is to keep your mouth shut and keep them guessing. If your 5' 9" 230 and your head is too small for your body they are gonna know anyway......for someone like me, who takes relatively low dosages, people don't know for sure. I've been open with other close friends in the gym who also take mainly so we can give each other advice. From my experience, there was no real value gained...only headaches when i have confided in close friends (outside the gym) and family members. If your girl is open to it and will support you then your lucky (and most likely a bit of gym rat herself). But be careful, your girl may leave your ass if she finds out or make your life a living hell. Been there. People outside the gym can be very quick to judge and give you a hard time.
I've been in situations where ive disclosed to my doc. I ended up at a doc with shortness of breath. Blood work came back with High Cholesterol (think i got my hands on some bad shit), so I told him whats up.