What are the new guidelines for continuous blood glucose (CBG) monitoring in patients with diabetes, considering factors such as age, medical history, treatment regimen, and lifestyle?

New Guidelines for Continuous Glucose Monitoring

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 by Patient Population

Type 1 Diabetes (Universal Recommendation)

• All children and adolescents with type 1 diabetes should be offered CGM, whether using multiple daily injections or insulin pumps, with benefits correlating directly with adherence to ongoing device use 2, 1
• Real-time CGM is approved for nonadjunctive use in children aged ≥2 years, and intermittently scanned CGM is approved for children aged ≥4 years 2
• All adults with type 1 diabetes capable of using CGM daily should receive it, particularly when not meeting glycemic targets, experiencing hypoglycemia unawareness, or having recurrent hypoglycemic episodes 1
• CGM in conjunction with intensive insulin regimens is a useful tool to lower HbA1c levels in selected adults (aged ≥25 years) with type 1 diabetes 2

Type 2 Diabetes (Selective Indications)

• Type 2 diabetes patients on intensive insulin therapy (≥3 injections daily or insulin pump) should use CGM to lower A1C and reduce hypoglycemia 1
• Patients experiencing unexplainable severe hypoglycemia, recurrent hypoglycemia, asymptomatic hypoglycemia, or nocturnal hypoglycemia require CGM 1
• Patients with unexplainable hyperglycemia, especially fasting hyperglycemia, benefit from CGM 1
• Dramatic glycemic variability despite self-monitoring of blood glucose warrants CGM use 1
• HbA1c above target despite multidrug oral and/or non-insulin injectable therapies is an indication for CGM 1

Pregnancy-Related Indications

• Real-time CGM in pregnant women with type 1 diabetes effectively improves A1C levels, time in range, and neonatal outcomes 1
• Gestational diabetes patients and women with pre-existing diabetes during pregnancy should use CGM as an adjunct to pre- and postprandial blood glucose monitoring 1

Hospital and Perioperative Settings

• 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

CGM Metrics and Glycemic Targets

Key Metrics to Monitor

• CGM metrics derived from the most recent 14 days (or longer for patients with more glycemic variability) should be used in conjunction with A1C whenever possible 2
• Time in range (70–180 mg/dL) is the primary metric for assessing glycemic control 2
• Time below target (<70 and <54 mg/dL) identifies hypoglycemia risk 2
• Time above target (>180 mg/dL) identifies hyperglycemia patterns 2

Target Ranges for Children and Adolescents

• An A1C of <7% (53 mmol/mol) is appropriate for many children 2
• Less stringent A1C goals (such as <7.5% [58 mmol/mol]) may be appropriate for patients who cannot articulate symptoms of hypoglycemia, have hypoglycemia unawareness, lack access to analog insulins or advanced technology, or cannot check blood glucose regularly 2
• Even less stringent A1C goals (such as <8% [64 mmol/mol]) may be appropriate for patients with a history of severe hypoglycemia or limited life expectancy 2

Usage Requirements for Effectiveness

Frequency of Use

• Real-time CGM devices should be used as close to daily as possible for maximal benefit, as the greatest predictor of HbA1c lowering with CGM for all age groups is frequency of sensor use 2, 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

Self-Monitoring Blood Glucose Integration

• Most patients receiving intensive insulin regimens (multiple daily injections or continuous subcutaneous insulin infusion) should self-monitor blood glucose before meals and snacks, at bedtime, occasionally after meals, when they suspect low blood glucose, after treating low blood glucose until normoglycemic, and before exercise and critical tasks like driving 2
• Many patients with type 1 diabetes require testing 6 to 10 (or more) times daily, although individual needs may vary 2

Critical Prerequisites and Patient Selection

Educational Requirements

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

Ongoing Evaluation

• When prescribed self-monitoring of blood glucose (SMBG), patients must receive ongoing instruction and regular evaluation of technique, results, and ability to use SMBG data to adjust therapy 2
• Providers must evaluate each patient's technique, both initially and at regular intervals thereafter 2

Important Contraindications and Limitations

Clinical Settings Where CGM Should Not Be Used

• Intensive care units are not suitable for CGM due to skin edema, vasoconstrictor drugs, hypotension, hypoxemia, and high-dose acetaminophen which adversely affect sensor accuracy 1

Patient-Related Contraindications

• CGM is not suitable for patients unwilling to learn device operation, as success depends on sustained use and proper data interpretation 1

Technical Limitations

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

Substances That Interfere with CGM Accuracy

• High-dose acetaminophen (at higher than therapeutic doses) can interfere with glucose meter accuracy 3
• Ascorbic acid (vitamin C) can affect CGM readings 3
• Uraemic toxins in patients with kidney disease may interfere with readings 3
• Certain medications like tetracycline and mannitol (for implantable sensors) can affect accuracy 3

Alternative CGM Use Patterns

Periodic 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

Special Clinical Situations

• Diabetes patients with gastroparesis should use CGM 1
• Special types of diabetes with dramatic glycemic variability should use CGM 1
• Endocrine disorders accompanied by dramatic glycemic variability should use CGM 1

HbA1c Testing Frequency

• Hemoglobin A1c should be tested at least twice per year in patients who are meeting treatment goals and who have stable glycemic control 2
• Quarterly HbA1c testing is required for those whose therapy has changed or who are not meeting glycemic goals 2
• Point-of-care testing for HbA1c allows more timely treatment changes 2

Common Pitfalls to Avoid

• Avoiding hypoglycemia should always take precedence over achieving HbA1c targets 2
• The frequency of SMBG should be reevaluated at each routine visit to avoid overuse 2
• Patients who have been using CGM successfully should have continued access after they turn 65 years of age 2
• The HbA1c level is an indirect measure of glycemia and may not accurately measure average glycemia in persons with increased turnover of red blood cells 2