This patient should measure her postprandial blood glucose level. Given the patient's young age and lack of other major comorbidities, her hemoglobin A1c goal is less than 6.5% to 7.0%. Postprandial hyperglycemia often remains undetected but still contributes to elevated hemoglobin A1c values. The effect is more profound when the hemoglobin A1c is close to 7.0%. Adequate meal-time coverage with insulin can be determined by measuring postprandial blood glucose levels. If her 1- to 2-hour postprandial blood glucose values are elevated above 180 mg/dL (10.0 mmol/L), her meal-time insulin should be increased or the composition of her meals should be altered to decrease her blood glucose. Changing her diet if it is causing postprandial hyperglycemia could eventually lead to lower insulin requirements.
Checking her postprandial blood glucose values first will help identify where the hyperglycemic issue arises that keeps her hemoglobin A1c above goal.
Increasing her glargine dose will not adequately affect postprandial hyperglycemia and may lead to overnight or fasting hypoglycemia.
Overnight glucose abnormalities can be identified with the measurement of a 3 AM blood glucose level. Large fluctuations in fasting blood glucose values or consistent fasting hyperglycemia can be clues to overnight hypoglycemia with subsequent rebound hyperglycemia (Somogyi effect) or hyperglycemia as a result of rising catecholamines (dawn phenomenon). The patient reports stable fasting and preprandial glucose values throughout the day. The most likely timing for glucose abnormalities that would affect her hemoglobin A1c value is in the postprandial state.
Sitagliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor that slows gastric emptying and suppresses glucagon secretion. Although it has a modest effect on hemoglobin A1c lowering, metformin remains first-line therapy for type 2 diabetes and should be continued as part of her regimen.