Yes, doctors do test for diabetes as a part of routine check up specially after the age of 30.
You are required to fast for 8-12 hours before testing.
Blood glucose test specifically the fasting sugar needs to be done with 8-12 hours fasting.
If your sugar levels are 170 then you are considered diabetic and you should consult a doctor immediately.
For a person without any type of diabetes, blood sugar levels are generally between 70 to 130 mg/dL post 6 hours of meals.