So often, we get asked this question.
"I did everything right, but my glucose is still rising!"
"I ate the same thing as yesterday and took the same number of units - but this time my glucose crashed afterwards."
The short answer is that there are countless factors that impact your glucose, and food is just one of them. A person with diabetes is confronted with choices constantly, every single day - what to eat, how much to dose, trying to anticipate where their glucose is headed. And while nowadays we have continuous glucose monitors to assist, there's still a significant amount of unpredictability in this process.
This graphic shows some of the variables in glucose control - some of which are under your control and some of which aren't. The right column of arrows shows what the research says about how certain factors impact glucose levels, while the left column shows that the writer has anecdotally noticed with his own glucose trends. Notice the discrepancies! Each individual's body (and their glycemic responses) behaves in a unique fashion.
So next time your confronted with an unexpected high or low glucose level, take a deep breath and stop blaming yourself! You are doing the best that you can with a very complex chronic disease.