Some clinics
test every patient at every visit. Others
test a selection of patients, some do not
test regularly at all.
I was with one clinic for 5 years, the first 3 years they didn't test at all, then it seemed like every 3rd visit they tested with a lab that they sent the samples to. That Dr closed up shop and my current clinic seems to test every 3rd visit using some type of dip-stick method done in office.