They have to order a seperate test for everything they are testing for so you can never legally be tested without your prior knowledge/consent. ( Canada anyhow)
Dont worry about the Dr office. If you get paranoid to go there you may decide not to go there sometime when you need to. Your DR works for you and his concern is your health and not busting you for something like pot. No worries.
Also the laws for posession are different all over if that is what you are referring to.
If you are talking about being high then no worries because they are not going to order up some tests just because you giggled or your eyes are red.
Also in lots of areas is not illegal to be high but just to grow, sell, posess, or drive while high. Its a hard and costly thing to prove and I dont know of any area that is wasting their cash on ppl with red eyes.
peace.