Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.
A 27-year-old woman is evaluated for management of her type 1 diabetes mellitus. She was diagnosed 10 years ago. She has no known complications from her diabetes. She eats a healthy diet and exercises an average of 60 minutes per day in the evening. She takes insulin glargine and insulin aspart. She is adherent with her insulin regimen and checks her blood glucose level three to five times per day. Her average blood glucose value is 125 mg/dL (6.9 mmol/L), with fasting glucose values ranging from 80 to 150 mg/dL (4.4-8.3 mmol/L). She routinely measures her 2-hour postprandial glucose values, and they are consistently less than 150 mg/dL (8.3 mmol/L). She has several overnight blood glucose values ranging from 90 to 140 mg/dL (5.0-7.8 mmol/L). Her HbA1c values over the last 6 months have been 7.3% to 7.5%. She is discouraged that her HbA1c values remain above 7.0%.
Laboratory studies, including creatinine and complete blood count, are normal.
Which of the following is the most appropriate management of her elevated HbA1c level?
A. Begin continuous glucose monitoring
B. Increase exercise
C. Increase insulin aspart
D. Increase insulin glargine
MKSAP Answer and Critique
The correct answer is A. Begin continuous glucose monitoring.
There is a discrepancy between this patient’s fingerstick blood glucose values and her HbA1c values that can be quickly reconciled with a 72-hour continuous blood glucose monitoring system. Continuous blood glucose monitoring systems use an electrochemical enzymatic sensor to measure the glucose content of interstitial fluid via insertion of a subcutaneous needle. In some systems data recording can be made available in real time to the patient, whereas other models store the data for later access and analysis. Since she does not have kidney disease or anemia that could affect the accuracy of HbA1c measurements, she likely has episodes of hyperglycemia not detected by her current monitoring efforts. Fingerstick blood glucose values only provide a small snapshot of the glucose variability that occurs throughout the day.
Undetected hyperglycemia or hypoglycemia can lead to significant differences between the fingerstick blood glucose values and the expected HbA1c level. Her wide range of fasting blood glucose values could be indicative of undetected overnight hypoglycemia. Intermittent continuous glucose monitoring is recommended when postprandial hyperglycemia, dawn phenomenon, or overnight hypoglycemia is suspected.
Lifestyle modifications are recommended for glycemic management; however, because this patient exercises in the evening, overnight hypoglycemia should be considered and evaluated with continuous glucose monitoring. Additional exercise may exacerbate the hypoglycemia.
This patient does not have evidence of postprandial hyperglycemia on her fingerstick blood glucose measurements, although it could be missed since she only measures after her meals periodically. Given the discrepancy in her blood glucose values and HbA1c level, hypoglycemia should be ruled out first before increasing her insulin doses that may increase the risk of hypoglycemia.
Key Point
- Continuous glucose monitoring may be useful in persons with postprandial hyperglycemia, dawn phenomenon, or overnight hypoglycemia.
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