I used to be pretty pedantic, and test 3 times per day - just to test what Carb food had more of an effect on my Insulin
You could easily test 2 - 1st in the morning and before bed
Some just test 1st in then morning
Eventually, you can Smell it (acetone)
The more you train, the more Carbs you need
You may also need more FATS in your diet if energy is low