kinda depends on how routine are your routines? Eating the same breakfast every day, then skip that one. But even some vegetables can differ in the individual responses and how close you are to prediabetes or no diabetes is going to allow a pop back that is quicker. Have an infetion? You better test. Once, when an antibiotic wasn't kicking in, I went to 635 and that happened within hours!
On vacation and not as in control of the old diet? More testing. Eating out where the kitchen might be slipping in an allergen like MSG or adding a balsamic reduction to that salad that usually is a non spiker? After church or at some other communal event while the personal who baked it claimed it has low carbs? They might be confused and doing that dairy free egg free standard that uses coke or seven up to raise it and a ine inch square is really 60 carbs. So, surprises eaten you'll know whether to ever trust again? More testing