A 38-year-old woman is evaluated for frequent episodes of hypoglycemia. She was diagnosed with type 1 diabetes mellitus 15 years ago and has been on continuous subcutaneous insulin infusions (CSII) with an insulin pump for 13 years. She checks her blood glucose level before meals and at bedtime. Several recent values have been between 40 mg/dL (2.2 mmol/L) and 60 mg/dL (3.3 mmol/L) at random times, which are asymptomatic. Fasting levels most mornings are between 110 mg/dL (6.1 mmol/L) and 180 mg/dL (10.0 mmol/L). She has a bedtime snack of 15 g carbohydrates each evening. Her only medication is insulin lispro administered by CSII.
Her most recent hemoglobin A1c level is 8.1%.
Which of the following is the most appropriate management?
A. Administer insulin with a bedtime snack
B. Change to multiple daily injections
C. Increase overnight basal insulin rate
D. Prescribe a continuous glucose monitoring system
MKSAP Answer and Critique
The correct answer is D. Prescribe a continuous glucose monitoring system. This item is available to MKSAP 19 subscribers as item 33 in the Endocrinology and Metabolism section. More information about MKSAP is online.
This patient with frequent hypoglycemia and hypoglycemia unawareness would benefit most from prescription of a continuous glucose monitoring system (CGMS) (Option D). Hypoglycemia unawareness is characterized by insufficient release of counterregulatory hormones and an inadequate autonomic response to hypoglycemia. Frequent episodes of previous hypoglycemia with resultant blunting of the counterregulatory response are often the inciting factor. A CGMS can alert the patient to low glucose values in the absence of warning symptoms and is a useful tool to decrease hypoglycemic events in patients with hypoglycemia unawareness. A CGMS can also help improve glycemic control and lower hemoglobin A1c if it is worn more than 50% of the time. This patient with a hemoglobin A1c of 8.1% needs improved glycemic control. The FDA has approved four CGMS devices for real-time insulin dosing as well as monitoring. The American Diabetes Association (ADA) endorses CGMS use in adults (age ≥18 years) with type 1 diabetes mellitus who are not meeting glycemic targets or have hypoglycemia or hypoglycemia unawareness. The ADA also endorses CGMS use in adults with type 2 diabetes to lower hemoglobin A1c.
Asking the patient to administer insulin with a bedtime snack (Option A) will not address her frequent episodes of hypoglycemia and may instead worsen her hypoglycemia. More detailed knowledge of her glycemic control over the course of the day is necessary before adjusting her insulin regimen.
A change to multiple daily injections (Option B) from continuous subcutaneous insulin infusions is unlikely to improve this patient's awareness of hypoglycemia or hemoglobin A1c level. More information on the patterns of glycemic control is needed before adjustments can be made to her insulin dosing.
For most healthy, young and middle-aged adults, the morning target glucose range is 70 mg/dL (3.9 mmol/L) to 180 mg/dL (10.0 mmol/L). Increasing the patient's overnight insulin rate (Option C) is unlikely to have a significant impact on her hemoglobin A1c level, as most of her morning blood glucose values are at or near target range. Increasing her overnight basal rates may also cause morning hypoglycemia.
- Hypoglycemia unawareness is characterized by insufficient release of counterregulatory hormones and an inadequate autonomic response to hypoglycemia.
- A continuous glucose monitoring system can alert the patient to low glucose values in the absence of warning symptoms and is a useful tool to reduce the frequency of hypoglycemic events in patients with hypoglycemia unawareness.