“This study has some limitations,” says Dr. Ganda. “First, participants were asked to monitor less than once a day, which is not frequent enough to provide the information needed to make appropriate changes to behavior or medication. By the end of the study, roughly half of the participants were monitoring less than twice a week. For home monitoring to help you reach your goals, you need to check more frequently, analyze the data, and make changes as necessary.”
A fasting blood glucose reading, taken first thing in the morning before you eat or drink anything, gives you a starting point for the day and helps to determine what is going on during the night. The American College of Endocrinology (ACE) recommends aiming for fasting levels below 110 mg/dl, while the Joslin Diabetes Center and American Diabetes Association (ADA) recommend shooting for a range of 90–130 mg/dl. If your readings are consistently higher than these goals, it may be because of the dawn phenomenon or a result of the Somogyi effect.
In the dawn phenomenon, hormones released in the very early morning cause increased insulin resistance, resulting in higher blood glucose levels. This occurs in everyone, with diabetes or without. However, in people who don’t have diabetes, extra insulin is secreted, so the rise in blood glucose level is minimal. Common preventive treatments for high morning blood glucose caused by the dawn phenomenon include getting daily exercise, eating a carbohydrate-containing bedtime snack, or adding the drug metformin (brand name Glucophage and others) to the diabetes control regimen.
The Somogyi effect, which is more likely to occur in people who use insulin, is a phenomenon in which low blood glucose during the night causes the body to release hormones that raise blood glucose levels, resulting in high morning levels. While a person’s first instinct for treating high morning readings may be to increase nighttime insulin, in fact, taking less insulin and going to bed with a higher blood glucose reading may be more effective at preventing the low that leads to the morning rise in glucose.
People who are experiencing high morning blood glucose levels are often encouraged to wake up at 3 AM on several occasions to check their blood glucose. High blood glucose at this time may point to the dawn phenomenon as the cause of the high morning readings, while low blood glucose at 3 AM may suggest the Somogyi effect.
Checking before meals
Similar to fasting readings, monitoring your blood glucose before meals gives you a baseline reading of your blood glucose before you eat. Some medical professionals call these preprandial readings.
“This is the best time to check your blood glucose, so you know what it is before you start the meal,” says Ananda Basu, M.D., associate professor and consultant in the Division of Endocrinology at the Mayo Clinic in Rochester, Minnesota. “Once you eat, your blood glucose is going to go up, but the baseline should be back to normal by the next meal.”
If your premeal readings are in the recommended range and your HbA1c test results are also in your target range, Dr. Basu says that monitoring after meals is not necessary. One reason is that blood glucose meters are most accurate when blood glucose levels are between 80 and 140 mg/dl, and after-meal spikes can exceed those levels. (For information about getting the most accurate readings from your blood glucose meter, check out “Getting Accurate Readings.” And to learn about using alternate sites to monitor, see “When Your Fingers Have Had Enough.”)