Who benefits from using a continuous glucose meter (CGM)?

Who Needs a Continuous Glucose Monitor

All patients with type 1 diabetes should use continuous glucose monitoring (CGM), regardless of age or current glycemic control, as this technology consistently reduces hypoglycemia and improves time in range without increasing adverse events. 1

Primary Indications for CGM

Type 1 Diabetes (Strongest Evidence)

• All children and adolescents with type 1 diabetes should be offered CGM, whether using multiple daily injections or insulin pumps, as benefits correlate directly with adherence to ongoing device use 1
• All adults with type 1 diabetes who are capable of using CGM daily should receive it, particularly when not meeting glycemic targets, experiencing hypoglycemia unawareness, or having recurrent hypoglycemic episodes 1
• Real-time CGM in pregnant women with type 1 diabetes effectively improves A1C levels, time in range, and neonatal outcomes 1

Type 2 Diabetes on Insulin Therapy

• Type 2 diabetes patients on intensive insulin therapy (≥3 injections daily or insulin pump) should use CGM to lower A1C and reduce hypoglycemia 1
• Hospitalized type 2 diabetes patients on insulin therapy in non-ICU settings benefit from real-time CGM to reduce glucose fluctuations and achieve stable glycemic targets without increasing hypoglycemia risk 1
• Perioperative glycemic control in type 2 diabetes patients is improved with real-time CGM 1

Type 2 Diabetes with Specific Glycemic Problems

CGM is indicated for type 2 diabetes patients using hypoglycemic therapy who experience any of the following 1:

• Unexplainable severe hypoglycemia, recurrent hypoglycemia, asymptomatic hypoglycemia, or nocturnal hypoglycemia
• Unexplainable hyperglycemia, especially fasting hyperglycemia
• Dramatic glycemic variability despite self-monitoring of blood glucose
• Patients who deliberately maintain high blood glucose due to fear of hypoglycemia
• HbA1c above target despite multidrug oral and/or non-insulin injectable therapies

Pregnancy-Related Diabetes

• Gestational diabetes patients and women with pre-existing diabetes during pregnancy should use CGM as an adjunct to pre- and postprandial blood glucose monitoring to achieve A1C targets and improve neonatal outcomes 1
• The American College of Obstetricians and Gynecologists specifically recommends CGM for pregnant women with type 1 diabetes with high-strength evidence 2

Special Clinical Situations

CGM is indicated for 1:

• Diabetes patients with gastroparesis
• Special types of diabetes with dramatic glycemic variability
• Endocrine disorders accompanied by dramatic glycemic variability

Educational and Behavioral Indications

Diabetes education purposes: CGM facilitates understanding of glucose changes from diet, exercise, alcohol, stress, sleep, and medications, motivating patients to establish healthy lifestyles and improving treatment adherence 1

Critical Prerequisites for CGM Use

Patient Capability Requirements

• Patients must be willing and able to learn the basic mechanical skills of the equipment, as optimal CGM use requires ongoing education and learning 1
• Robust diabetes education, training, and ongoing support are required for optimal implementation 1, 2
• Users need ability to perform self-monitoring of blood glucose for calibration (device-dependent) and verification of readings when discordant from symptoms 1

Usage Frequency for Effectiveness

• Real-time CGM devices should be used as close to daily as possible for maximal benefit 1
• Intermittently scanned CGM devices must be scanned at minimum once every 8 hours 1
• Benefits of CGM correlate directly with adherence to ongoing device use 1

Important Contraindications and Limitations

Where CGM Should NOT Be Used

• Intensive care units: Skin edema dilutes interstitial fluid glucose causing inaccurate results; vasoconstrictor drugs decrease skin blood flow and slow glucose shift from capillaries to interstitial fluid; hypotension, hypoxemia, and high-dose acetaminophen adversely affect sensor accuracy 1

Patient Selection Pitfalls

• CGM is not suitable for patients unwilling to learn device operation, as success depends on sustained use and proper data interpretation 1, 2
• Insufficient evidence exists for screening or diagnosis of prediabetes or diabetes 2

Technical Limitations to Counsel Patients About

• CGM measures interstitial fluid glucose, which lags behind blood glucose by 5-15 minutes during rapid changes 2
• Accuracy is lowest in hypoglycemic ranges, a critical limitation for patients with problematic hypoglycemia 2
• Sensor accuracy affected by medications, temperature, humidity, and altitude 2
• Skin reactions (irritation or allergy) should be assessed and addressed to aid successful device use 1, 2
• Avoid exposure to strong magnetic fields, MRI, and in some devices conventional X-ray and CT scanning 1

Periodic/Professional CGM Use

Periodic use of real-time, intermittently scanned, or professional CGM can be helpful when continuous use is not appropriate, desired, or available 1

Blinded CGM data, when coupled with diabetes self-management education and medication dose adjustment, helps identify and correct patterns of hyper- and hypoglycemia in both type 1 and type 2 diabetes 1