The last time my Metformin prescription was refilled (by a new doctor), he gave me Metformin Extended Release instead of regular Metformin. My numbers have been higher since then. Could the medicine be to blame? My diet hasn't really changed much.

Yes.

Metformin is a drug which is effective only if it is present in your body at the time the food is being assimilated. That makes Metformin ER a good drug of choice for those who eat many small meals. If you are a person who tends to eat a big meal once or twice a day, it really is a poorer choice than regular fast-acting Metformin taken with your meal.

The "bulk" of your digestion occurs from 1 hour to 4 hours after eating the food. Fats take the longest, followed by proteins, and the fastest is carbs.

This works out quite well for Metformin taken with the meal.... it has its highest levels during the bulk of the cell-assimilation process. This is why ER gives you higher "numbers". The extended-release is placing some of the drug in your body at times when it's
"wasted" - the food is gone.....Correspondingly, when the food is in the assimilation queue, less of the metformin is available.

By "numbers" - I am assuming you mean glucometer measurements. This is a "snapshot" of your blood sugar level at an instant in time. It doesn't show the time-profile of your sugar, which is the parameter you really want to control. A brief high sugar which is reduced quickly has less effect, long-term, to your organs than a maintained high sugar level over decades.

My original doctor had me on Metformin at night before I went to bed my A1C numbers stayed around 5.7. I am afraid it will be higher this time since I have been on the extended relase for a few months now. And yes, I tend to eat big meals rather than several small ones. Thanks for the info.