Unexplained High Blood Glucose
How many people with type 2 diabetes are struggling with high fasting glucose in the morning after values appear normal at bedtime? What explains this fluctuation? What practical actions can people take to normalize their blood sugars before noontime? Also, is there any way to narrow the spread of fasting blood glucose values, by taking some action the evening before? What options are available to us besides prescription medications? Joseph Rubin, Southfield, Michigan
Roger P. Austin, MS, RPh, CDE, responds: High fasting blood glucose levels are quite common in people with type 2 diabetes. There are two physiological processes that contribute to this: One is the excessive release of stored glucose from the liver in people with type 2, and the second is the so-called "dawn phenomenon" of early cortisol release, which occurs as part of the daily diurnal cycle of humans.
First, the liver releases stored glucose at an excessive rate in people with type 2 diabetes. This occurs even though insulin levels are quite high, as in the early stages of the disease. This has been described as "hepatic [liver] resistance to insulin." Type 2 diabetes is also characterized by the progressive loss of insulin-producing capacity of the pancreas over time. As insulin levels fall, glucagon levels rise, and because glucagon stimulates the liver to release stored glucose, fasting blood glucose levels continue to rise.
Everyone, including people who don't have diabetes, experiences the dawn phenomenon to varying degrees. The body produces increased levels of both growth hormone and cortisol beginning around 4 to 5 a.m. These hormones cause an increase in blood glucose in people with diabetes.
Some steps that can be taken to blunt this fasting rise of blood glucose include eating dinner at an earlier time (6 or 7 p.m. rather than 9 or 10 p.m.), as well as being physically active early in the evening by doing something like walking or bicycling.
Late evening snacking can also cause increased morning blood glucose levels. For those who are interested, there are also a number of very effective pharmacologic options to treat this condition. These include metformin; the incretin mimetics, such as exenatide; basal insulins, such as insulin detemir or insulin glargine; and insulin pump therapy.