suggestions please.

i cant stop thinking about it and i need to write it before i pass out from all the nighttime cough medicine i took,in a couple months i am sapost to have a blood test to see all my blood levels are good,and iron stuff like that,but i am on meds im sapost to be taking, and i havent took them in months,is it legal for them to look at other levels and stuff in your blood without you knowing, and if even if its for something picific, do they check everything?even wen they say its for one thing?