Since you decided to spill the beans here is some more info:
If you do have failure to control BP after a few months he would have been ordering these and a few other tests anyway. If playing with different meds/doses isn't working you start to wonder if the person has Secondary Hypertension (high BP caused by some other cause, like hormones or tumors).
I could sit here and give you a whole differential on different causes or you could just go to your freaking doctor and get the full set of labs drawn (payed by insurance this time).