Did your physician suggest you come into their facility to dump a pint of blood or ..."hey, run down to the blood bank and phlebot"...?
If the latter, you should discuss with your physician to either set you up therapeutics at a blood bank, e.g, Red Cross or similar. Or have you come into their facility to phlebotomize.
S/he shouldn't leave it up to you to find some random blood bank to phlebot as you 'may' get denied at a blood bank.
This goes without mentioning, s/he should discuss with you if there may be a secondary stimuli of erythropoiesis or your dosage needs adjusted.
Other than what Gizmo stated with hematocrit being the one to cue in on with hyperviscosity. Your platelets are of importance in this discussion, too.