i wouldn't tell the truth... the possibility of it getting back to your insurance company alone isn't worth the risk. yeah chances are that it will never get back to your insurance but it has happened and just the precedence alone is reason enough for me to err on the side of caution. and being that my wife and family don't know, this would not be a good way for them o find out...
i had an infection in my quad in the spring from an inject, went to the doc and played stupid... he made his own assessment said i probably just had a small muscle tear in my quad and it got infected, and this is a sports medicine doc...
remember that the doc's office is a business and you are a customer... you don't need to tell him anything unless it will affect your treatment... he does not need to know that your on.
there are times i would absolutely tell him but in this kind of circumstance the risk outweighs the benefit
~dim