What is the dawn phenomenon?

From the Guidelines

The dawn phenomenon is a natural increase in blood glucose levels that occurs in the early morning hours, caused by counter-regulatory hormones such as cortisol and growth hormone. This phenomenon is relevant in the context of insulin pump therapy, where the basal rate is programmed to deliver small doses of insulin as a constant infusion over 24 hours, taking into account factors such as insulin sensitivity and the dawn phenomenon 1.

Key Points to Consider

• The dawn phenomenon typically occurs between 3 AM and 8 AM, resulting in higher morning blood sugar readings for people with diabetes.
• Counter-regulatory hormones like cortisol and growth hormone increase glucose production and decrease insulin sensitivity to prepare the body for waking.
• To manage the dawn phenomenon, individuals can check blood sugar levels before bed and upon waking to confirm the pattern, and consider treatment options such as:
  • Adjusting medication timing, such as taking insulin or oral medications closer to bedtime or using long-acting insulin.
  • Having a small protein snack before bed to stabilize overnight glucose.
  • Avoiding carbohydrates late at night.
  • Exercising in the evening to improve insulin sensitivity.
• For insulin pump users, programming a higher basal rate during early morning hours can help mitigate the effects of the dawn phenomenon, as the pump provides very stable insulin administration and excellent blood glucose control in the fasted state 1.

Clinical Implications

The dawn phenomenon is an important consideration in the management of diabetes, particularly for individuals using insulin pump therapy. By understanding the causes and effects of this phenomenon, healthcare providers can work with patients to develop effective strategies for managing morning blood sugar readings and improving overall glucose control. Regular monitoring is essential to determine if interventions are effective, and medication adjustments may be necessary if morning blood sugars remain consistently high despite these strategies.

From the Research

Definition of the Dawn Phenomenon

• The dawn phenomenon is a condition characterized by an increase in fasting levels of plasma glucose or insulin requirements between 5 and 9 a.m., in the absence of antecedent hypoglycemia 2.
• It is defined as a hyperglycemia or an increase in the amount of insulin needed to maintain normoglycemia, occurring during the early morning hours, with a magnitude of more than 10 mg/dL or an increase in insulin requirement of at least 20% from the overnight nadir 3.

Prevalence and Variability

• The dawn phenomenon occurs commonly in both non-insulin-dependent and insulin-dependent diabetes mellitus, with approximately 54% of patients with type 1 diabetes and 55% of patients with type 2 diabetes experiencing the phenomenon 3.
• The phenomenon is highly variable, with insulin requirements increasing at least 50% for 1 1/2 hours in 77% of patients with non-insulin-dependent diabetes mellitus and in 75% of patients with insulin-dependent diabetes mellitus 2.

Pathogenesis and Management

• The most likely pathogenic mechanism underlying the dawn phenomenon is growth hormone-mediated impairment of insulin sensitivity at the liver and muscles 3.
• Therapeutic decisions aimed at correcting fasting hyperglycemia should take into account the variability and magnitude of the dawn phenomenon within individual patients 3.
• A dual-basal-insulin regimen, using a long-acting glargine and an intermediate-acting neutral protamine Hagedorn (NPH), has been shown to be effective in overcoming early morning hyperglycemia due to insulin resistance in the dawn phenomenon 4.
• Continuous subcutaneous insulin infusion (CSII) can also provide good overnight glycemic control and minimize the dawn phenomenon, with a marked dawn phenomenon being rare when a single but adequate basal infusion rate is used 5.

Clinical Implications

• The dawn phenomenon is a large component of postbreakfast hyperglycemia, and targeting insulin titration to this glucose level may result in excessive basal insulin dosing for non-dawn phenomenon periods of the day 6.
• Consideration should be given to pretreating the earlier dawn phenomenon with an insulin pump using a variable basal insulin rate, rather than increasing the morning premeal insulin bolus 6.