Prediabetes and Type 2 diabetes are progressive conditions that changes over time. Many people experience shifts in their body’s natural ability to manage blood sugar even with careful management. This is typical and not a reflection of you doing a "bad job" managing things. Your body changes and so will your diabetes. Your role is to do your best, identify new patterns and let your endocrinologist or CDCES know when changes are occurring. To understand why blood glucose levels increase over time, it is important to understand the concepts of insulin resistance & decreasing insulin production.
Increasing Insulin Resistance
As you grow older, cells in your body will gradually become more resistant to insulin. The first sign of this is a rise of your fasting blood glucose. This is considered a part of normal aging, but it can be more prominent in some people than others due to genetic factors or lifestyle.
Decreasing Insulin Production
While insulin resistance plays a large role in blood sugar control, the most important factor of diabetes is a decrease in production of insulin. This decrease is rather sudden and happens over the course of a few years before being diagnosed. This sudden drop in insulin production is often referred to as β-cell dysfunction. It is caused both by loss of cells producing insulin (β-cells) and decreasing function of the available cells.
A Step-wise Progression to Diabetes
An increase in insulin resistance is the primary cause of pre-diabetes while the loss of insulin production marks the start of type 2 diabetes. This progression can be illustrated by the graph below, showing how glucose levels and circulating insulin levels typically change over time as blood sugars go from normal ranges (green) to pre-diabetes (yellow) to type 2 diabetes (orange).
Surprising to many, blood glucose levels have been above normal many years before you were diagnosed.
Remember, as you age your body changes. And as you change so too will the way you manage your diabetes.