What else do phyisicians screen urine for other than drugs?

[kaiser soze]

Just curious, I have blood work to do monday and the person on the phone told me to not after 12am and to drink water/coffee/tea for a urine screening

I didn't ask why initially, but will if they ask

is this something to do with my blood? I'm paranoid they're going to drug test....and they have no right to considering I'm not employed by my physician

oh, this is VA related...hmm