What is the target blood sugar range on a Continuous Glucose Monitor (CGM)?

Target Blood Sugar Range on CGM

For most adults with diabetes, the target blood sugar range on CGM is 70-180 mg/dL (3.9-10.0 mmol/L), with a goal of spending more than 70% of time in this range. 1

Core CGM Target Ranges

Time in Range (TIR)

• Target: >70% of readings between 70-180 mg/dL for most nonpregnant adults with diabetes 1, 2
• Each 5% incremental increase in TIR provides clinically meaningful benefits 2, 3
• This target correlates with an A1C goal of <7% and is associated with reduced risk of microvascular complications 1

Time Below Range (TBR) - Hypoglycemia Targets

• Level 1 hypoglycemia (54-69 mg/dL): <4% of time 1, 2
• Level 2 hypoglycemia (<54 mg/dL): <1% of time 1, 2
• Minimizing severe hypoglycemia (<54 mg/dL) is critical as it can cause lasting neurological damage, particularly in children 4

Time Above Range (TAR) - Hyperglycemia Targets

• Total TAR: <25% of time above 180 mg/dL 2, 3
• Level 1 hyperglycemia (181-250 mg/dL): included in the 25% total 1
• Level 2 hyperglycemia (>250 mg/dL): should be minimized as much as possible 1, 2

Additional Key Metrics

Glycemic Variability

• Coefficient of variation (CV) target: ≤36% 1
• Some evidence suggests CV <33% provides additional protection against hypoglycemia for patients on insulin or sulfonylureas 1
• Lower CV may be more important than higher TIR for preventing hypoglycemia in older adults 5

Data Collection Requirements

• Minimum 14 days of CGM wear with at least 70% active sensor time (approximately 10 days of data) for reliable assessment 1, 2
• This duration captures sufficient glycemic variability to guide treatment decisions 1, 2

Modified Targets for Special Populations

Older Adults and High-Risk Individuals

• TIR: >50% (≥12 hours/day) in range 70-180 mg/dL 2
• TBR: <1% (<15 minutes/day) below 70 mg/dL - more stringent to prevent falls and cognitive impairment 2, 5
• TAR: <10% (<2 hours, 24 minutes/day) above 250 mg/dL 2
• These less stringent targets prioritize hypoglycemia avoidance in vulnerable populations 1, 5

Children and Adolescents

• Same TIR goal of >70% (70-180 mg/dL), but this target is difficult to achieve without automated insulin delivery systems due to irregular lifestyles and day-to-day variability 1, 4
• Prioritize TBR <5% over achieving TIR >70% in pediatric patients not using automated systems, as hypoglycemia prevention is paramount 4
• Severe hypoglycemia in children <6 years can adversely affect brain development 1

Pregnant Individuals

• Different target range: 63-140 mg/dL (3.5-7.8 mmol/L) - narrower than standard targets 2
• Specific TIR targets differ from non-pregnant individuals to optimize maternal and fetal outcomes 2

Clinical Context and Interpretation

Relationship to A1C

• TIR >70% typically correlates with A1C <7% 1
• The Glucose Management Indicator (GMI) provides a calculated A1C estimate from mean CGM glucose 1
• CGM provides more actionable real-time data than A1C, which only reflects a 2-3 month average and can be affected by anemia, hemoglobinopathies, and pregnancy 2

Normal Physiology Reference

• In people without diabetes, CGM shows approximately 87% time in 70-140 mg/dL range, with about 12% of time above 140 mg/dL and brief excursions above 180 mg/dL (>15 minutes/day on average) 6
• This context helps clinicians understand that even individuals without diabetes experience some glucose variability 6

Common Pitfalls to Avoid

• Don't focus solely on mean glucose - it misses critical information about hypoglycemia and variability 2
• Don't collect insufficient data - less than 14 days or <70% sensor wear time yields unreliable patterns 1, 2
• Don't ignore glycemic variability (CV) - high variability increases hypoglycemia risk even with acceptable TIR 1, 5
• Don't apply one-size-fits-all targets - individualize based on age, comorbidities, hypoglycemia risk, and life expectancy 1, 2
• Don't overtighten targets in vulnerable populations - this increases hypoglycemia risk without clear benefit 2, 5

Standardized Reporting

Use the Ambulatory Glucose Profile (AGP) as a standardized single-page report that includes all 10 core CGM metrics with visual cues for easy interpretation 1, 2