Aunt Wang’s situation, where her fasting blood glucose level increased despite not eating or drinking overnight, is not uncommon among patients with diabetes. There are two main phenomena that could explain this: the “dawn phenomenon” and the “Somogyi phenomenon.”
Dawn Phenomenon
This occurs when blood sugar is well controlled during the night without any hypoglycemic events, but there is a rise in blood sugar in the early morning hours (from 3 a.m. to before breakfast). The reason behind this is the increased secretion of hormones like growth hormone, glucocorticoids, and catecholamines from midnight to morning, which raise blood sugar levels. In diabetic patients, insufficient insulin secretion or function cannot counteract the effects of these hormones, leading to a gradual increase in blood sugar at dawn. This phenomenon is often related to the inadequate dosage of medication, particularly in patients with a longer duration of diabetes.
Somogyi Phenomenon
This refers to the occurrence of nocturnal hypoglycemia, which triggers the body to produce a large amount of hormones that raise blood sugar levels (such as glucocorticoids, catecholamines, and glucagon) to maintain stability. This results in increased fasting blood sugar, essentially a hyperglycemic response to hypoglycemia. Hypoglycemia typically occurs around 0 to 3 o’clock, leading to elevated fasting blood sugar in the morning. The Somogyi phenomenon is often seen in patients who are on excessive insulin doses, miss meals, or increase physical activity without adjusting their medication.
To differentiate between the two, the most common clinical method is to monitor fasting blood glucose levels at 0 and 3 o’clock. If there is no nocturnal hypoglycemia and blood sugar rises gradually after midnight, it is the dawn phenomenon. If hypoglycemia (≤3.9 mmol/L) occurs before and after dawn, or if the patient experiences symptoms such as anxiety, chest tightness, excessive sweating, hunger, irritability, and fasting blood glucose is > 8.0 mmol/L, it is the Somogyi phenomenon.
Treatment for these phenomena differs due to their distinct causes. For patients with the dawn phenomenon, the dosage or type of hypoglycemic medication may need to be adjusted under a doctor’s guidance, and insulin users may rotate injection sites. Patients with the Somogyi phenomenon may need to reduce the insulin dose before dinner (or before bed) or adjust the dosage of oral hypoglycemic drugs under a doctor’s guidance, and ensure appropriate meals before bed to prevent nocturnal hypoglycemia.
It’s important for patients to monitor their blood sugar levels at night to identify whether they are experiencing the dawn phenomenon or the Somogyi phenomenon, which will guide the adjustment of medication. Many elderly patients may not have obvious symptoms during nocturnal hypoglycemia, so it’s crucial to pay attention to avoid the potential harm of hypoglycemia and the subsequent rebound hyperglycemia.
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