Hi, you're not testing fasted, are you?
"Postprandial hyperglycemia is also one of the earliest abnormalities of glucose homeostasis associated with type 2 diabetes"
So test 1-2 hours after a meal. As a pure guess, I'd think that once a month is sufficient - unless you change your diet or activity or other risk factors.
Agree with Ken_PA. Testing from time to time. Occassionally test fasting. Ideally it will be 95 or less. Occassionally test 2 hours after eating, it should be less than 120 - 140, though less than 100 is totally normal.
You could also do annual hba1c blood tests. Completely normal is less than 5. 5.7 will get you diagnosed as prediabetic, and 6.5 or so will get you diagnosed as diabetic.