Real information, discussed with your provider, is more useful than a guess.
In my years in practice, I watched a lot of people make decisions about their own health from assumptions rather than actual numbers. That wasn't always a problem. But often a single data point, brought into a conversation with a healthcare provider, would have replaced a guess with something solid to talk about. I've come to believe that having real information, and then talking it through with someone who knows your history, tends to serve people better than guessing does. An at-home A1c test is one small example of that kind of information.