A 10-year-old child with type 1 diabetes mellitus has HbA1c consistently above 9% despite multiple daily injections. His fasting glucose in the morning is persistently high. His continuous glucose monitoring (CGM) data shows glucose values rising between 3–8 AM without a preceding nocturnal hypoglycemia. What is the most likely cause and management?
- A Somogyi phenomenon; reduce evening NPH insulin dose
- B Insulin waning; change to a premixed insulin regimen
- C Dawn phenomenon; increase the evening long-acting insulin dose or shift timing ✓
- D Nocturnal hypoglycemia with rebound; reduce bedtime snack
Explanation
The dawn phenomenon is characterized by rising blood glucose levels in the early morning hours (3–8 AM) without preceding hypoglycemia. It results from the physiological surge of counter-regulatory hormones (growth hormone, cortisol, glucagon) in the early morning, which decrease insulin sensitivity and increase hepatic glucose production. CGM data showing a clean rise from midnight onward (without prior dip) confirms dawn phenomenon rather than Somogyi (rebound hyperglycemia after nocturnal hypoglycemia). Management includes increasing the dose of long-acting insulin (e.g., glargine/detemir), shifting its administration to bedtime, or using an insulin pump with an increased basal rate program during early morning hours. Somogyi phenomenon would show a nocturnal glucose dip followed by a rise.
Reference: Ghai Essential Pediatrics, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.