A fasting blood sugar 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 the American Diabetes Association (ADA) recommend a range of 80–130 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 sugar 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 sugar level is minimal. Common preventive treatments for high morning blood sugar 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 sugar during the night causes the body to release hormones that raise blood sugar 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 sugar reading may be more effective at preventing the low that leads to the morning rise in glucose.
People who are experiencing high morning blood sugar levels are often encouraged to wake up at 3 AM on several occasions to check their blood sugar. High blood sugar at this time may point to the dawn phenomenon as the cause of the high morning readings, while low blood sugar at 3 AM may suggest the Somogyi effect.