What are the evidence-based indications for Continuous Glucose Monitoring (CGM) in patients with Diabetes Mellitus Type 2 (DM2)?

Evidence-Based Indications for Continuous Glucose Monitoring in Type 2 Diabetes

Continuous glucose monitoring (CGM) in type 2 diabetes is primarily indicated for patients on intensive insulin therapy, those with significant glycemic variability, and individuals experiencing problematic hypoglycemia, as these populations demonstrate the greatest mortality and morbidity benefit from CGM use.

Primary Indications for CGM in Type 2 Diabetes

Insulin-Related Indications

• Intensive insulin therapy: Patients requiring multiple daily injections (≥3 times/day) or insulin pump therapy 1, 2
• Basal insulin therapy: Patients on basal insulin who experience any of the following 3:
  • Unexplained severe hypoglycemia
  • Recurrent hypoglycemia
  • Asymptomatic hypoglycemia
  • Nocturnal hypoglycemia

Glycemic Control Issues

• Problematic hypoglycemia 1, 2:
  • Unexplained severe hypoglycemia
  • Recurrent hypoglycemia
  • Asymptomatic hypoglycemia
  • Nocturnal hypoglycemia
  • Hypoglycemia unawareness
• Significant glycemic variability despite standard monitoring 1, 4
• Refractory hyperglycemia, especially fasting hyperglycemia 1
• HbA1c above target despite multiple oral and/or non-insulin injectable therapies 1

Special Clinical Situations

• Hospitalized patients on insulin therapy in non-intensive care units 1
• Perioperative glycemic control in type 2 diabetes patients 1
• Fear of hypoglycemia leading to intentional maintenance of high blood glucose levels 1

Types of CGM for Type 2 Diabetes

Real-Time CGM

• Provides continuous glucose readings with alerts/alarms
• Most beneficial for:
  • Patients at high risk for hypoglycemia 1
  • Hospitalized patients on insulin therapy 1
  • Perioperative patients 1

Intermittently Scanned CGM

• Requires user to scan sensor for readings
• Appropriate for most type 2 diabetes patients requiring CGM 2
• Particularly useful for patients on basal insulin 3

Professional/Blinded CGM

• Short-term diagnostic tool used intermittently
• Useful for:
  • Identifying glucose patterns in patients not on intensive insulin 1
  • Guiding medication adjustments 1
  • Educational purposes to demonstrate impact of diet, exercise, and medications 1

Clinical Benefits of CGM in Type 2 Diabetes

Improved Glycemic Outcomes

• Prevents glycemic deterioration in well-controlled patients (HbA1c <8%) on insulin therapy 5
• Reduces HbA1c by approximately 0.4% in patients on basal insulin compared to standard monitoring 3
• Increases time in target glucose range (70-180 mg/dL) by approximately 15% 3
• Reduces time spent in hyperglycemia (>250 mg/dL) by approximately 16% 3

Hypoglycemia Detection and Prevention

• Identifies patterns of hypoglycemia that may be missed with traditional monitoring 2
• Particularly valuable for detecting nocturnal hypoglycemia 1, 2
• Helps identify factors contributing to hypoglycemia, such as high glycemic variability 4

Implementation Considerations

Patient Selection Factors

• Technical capability: Patient must be able and willing to learn device operation 1
• Self-monitoring capability: For devices requiring calibration, patient must be able to perform SMBG 1
• Educational readiness: Patient should be willing to use CGM data to modify behavior 1

Contraindications and Cautions

• Intensive care settings: Not recommended due to potential inaccuracies 1
• Skin edema: May dilute interstitial fluid glucose readings 1
• Vasoconstrictor drugs: May decrease skin blood flow affecting accuracy 1
• Hypotension or hypoxemia: May affect sensor accuracy 1
• High-dose acetaminophen: May interfere with some CGM systems 1

Clinical Pearls

• CGM is not universally recommended for all type 2 diabetes patients, particularly those well-controlled on diet and/or oral agents alone 1
• The benefits of CGM correlate with adherence to ongoing use of the device 1
• Real-time CGM devices should be used as close to daily as possible for maximal benefit 1
• Intermittently scanned CGM devices should be scanned frequently, at minimum once every 8 hours 1
• Professional CGM use should always be coupled with analysis, interpretation, and education 1
• When evaluating CGM data, focus on time in range (70-180 mg/dL), time below range, and glycemic variability 2

Common Pitfalls to Avoid

• Prescribing CGM without providing adequate education and training 1
• Using CGM in patients unwilling to learn basic mechanical skills of the equipment 1
• Failing to recognize interfering substances that may affect specific CGM systems 1
• Not considering cost and insurance coverage when selecting CGM systems 2
• Overlooking the need for regular follow-up to review CGM data and adjust treatment plans 2

By following these evidence-based indications and implementation strategies, clinicians can appropriately select type 2 diabetes patients who will benefit most from CGM technology, ultimately improving glycemic control, reducing hypoglycemia risk, and enhancing quality of life.