CGM Data Interpretation and Treatment Adjustment in Type 2 Diabetes
A 62-year-old woman with T2D for 8 years, on basal-bolus insulin (glargine 30 units at bedtime, aspart 8 units TID with meals), metformin 1000 mg BID, and empagliflozin 10 mg daily. Her HbA1c is 7.8%. She recently started using a real-time CGM. Her CGM report shows: TIR 62%, TBR 10% (5% below 54 mg/dL), TAR 28% (20% above 250 mg/dL). The glucose profile shows a pattern of high glucose overnight (200–250 mg/dL) and frequent lows in the late afternoon (3–5 PM) and occasionally after breakfast. She reports late afternoon lows are symptomatic. She sometimes skips lunch due to work. Her BMI is 28 kg/m², eGFR 70 mL/min/1.73 m².
1. Interpret her CGM metrics and identify the likely causes of the glucose patterns. What changes would you make to her insulin regimen?
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TIR 62% is below goal (>70%), TBR 10% is high (goal <4%), and TAR 28% is high. The overnight highs suggest basal insulin is insufficient or there is a dawn phenomenon. The late afternoon lows likely relate to the lunchtime aspart dose combined with skipped lunch (missing carbohydrates) and possibly the peak of the morning glargine? Glargine is peakless, so more likely the aspart at lunch if she skips lunch but takes insulin? Actually she skips lunch, so if she takes aspart with lunch but doesn't eat, that causes hypoglycemia. Also, the morning aspart could cause late morning lows, but the pattern is late afternoon. The post-breakfast lows could be due to excessive breakfast bolus. Adjustments: increase basal insulin (glargine) by 2–4 units to address overnight highs, but monitor for nocturnal hypoglycemia. For late afternoon lows: if she skips lunch, she should not take the lunchtime aspart, or reduce it; alternatively, adjust to a more flexible regimen. Consider reducing breakfast aspart if post-breakfast lows persist. Review her insulin-to-carb ratio and correction factor. Consider switching to insulin degludec for more stable basal. Also, review empagliflozin (may contribute to ketosis but not hypoglycemia). Provide education on meal planning and not skipping meals, or using rapid-acting insulin only when eating. Recommend CGM alerts for lows. Reassess in 2 weeks.
2. What DSMES and technology education would you provide to help her improve her TIR and reduce hypoglycemia?
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Education: interpret CGM data with her, teach pattern management (look at 3–5 days of data), set realistic goals. Teach her to use CGM arrows and alerts to prevent lows, and to treat hypoglycemia with 15 g fast carbs. Discuss meal planning: consistent meals or adjust insulin for skipped meals. If she skips lunch, she should not take lunch aspart, or take a reduced dose if she eats a small meal. Review sick-day rules. Teach her to share CGM data with the clinic. Address her work schedule and find solutions. Consider referral to a dietitian for practical meal strategies. Emphasize that CGM can help her see the impact of food and insulin timing. Set up a follow-up to review data and adjust. Also, discuss the use of CGM in driving and safety.