It depends how you are using the information. If you’re testing just because you’ve been told to and don’t do anything with the information, then it’s a waste of time. However, a lot of people find it useful to see how different foods affect their blood sugar levels. In which case, test just before you start eating and again 2 hours later, and if you have risen more than 3mmol/l then perhaps there was too much carbohydrate in the meal for your body to cope with. So try again with a smaller portion or subtituting the carbs for something else. Once you’ve got used to what your body can and can’t cope with, then you can safely scale down the testing and just do occasional checks to make sure things are still working OK. If you need to get your hba1c down then you can’t know how to do that unless you see exactly how different foods affect you. People are not all the same and what one person can get away with, another can’t touch with a barge pole.