You can't eat anything before a diabetes test, because it somehow influences the results. I think the test measures how your body reacts to lowered blood sugar, but I don't exactly remember. Sounds kinda like she really wants you to get a diabetes test.

A lot of the time general practice doctors don't give kids drug tests at the request of parents. Often they refer the parent to a lab that does that kind of stuff, or to one of the home tests. Also, most drug tests are urinalysis tests rather than blood tests because they're cheaper.

If you are 18 or over(in the US, I don't know the laws anywhere else), you can ask the doctor exactly what he plans to test for, and he has to tell you. Because an 18 year old is legally an adult, you must give consent for any procedures to be done, and not your parents. If he says it is a drug test you just refuse to allow them to do it.

Anyway, it sounds to me like you're not going to get a drug test. Hope that helps.