Time in Range (TIR) in Diabetes: CGM Metrics

Q: What is time in range diabetes and how is it used in clinical research and healthcare?

Time in Range (TIR) is the percentage of time per day that a patient’s continuous glucose monitoring (CGM) readings stay within the target glucose range of 70 to 180 mg/dL (3.9 to 10.0 mmol/L), with a standard clinical goal of >70% (>16 hours and 48 minutes per day) for most adults with type 1 or type 2 diabetes. In clinical care and therapeutic clinical trials, TIR is used alongside Time Below Range (TBR), Time Above Range (TAR), Glycemic Management Indicator (GMI), and coefficient of variation (%CV) to quantify glycemic excursion patterns that HbA1c cannot detect.

Time in range diabetes (TIR) is a standardized continuous glucose monitoring (CGM) metric defined as the percentage of time over a specified observation period—or the equivalent number of hours and minutes per day—that an individual’s interstitial glucose readings remain within a target glycemic interval, defined for most adults with type 1 or type 2 diabetes as 70 to 180 mg/dL (3.9 to 10.0 mmol/L).

Formalized by the 2019 International Consensus on Time in Range (Battelino et al., Diabetes Care) and incorporated into the American Diabetes Association (ADA) Standards of Care in Diabetes, TIR addresses the critical analytical limitations of hemoglobin A1c (HbA1c). Whereas HbA1c reflects only mean glycemia over 2 to 3 months and is confounded by hemoglobinopathies, anemia, chronic kidney disease, and variable red blood cell lifespan, continuous glucose monitoring metrics quantify acute hypoglycemia, postprandial hyperglycemia, and day-to-day glycemic variability across clinical care and therapeutic clinical trials.

Core CGM Glycemic Definitions and Mathematical Formulation

In both ambulatory diabetes care and clinical trial protocols, TIR is never interpreted in isolation; it is evaluated alongside complementary metrics that partition the 24-hour glycemic distribution into five standardized zones, plus central tendency and dispersion indicators:

TIR (%) = (Number of valid CGM readings between 70 and 180 mg/dL / Total valid CGM readings) × 100
%CV     = (Standard Deviation of CGM glucose / Mean CGM glucose) × 100
GMI (%) = 3.31 + (0.02392 × Mean CGM glucose in mg/dL)

Time in Range (TIR): Percentage of readings and time per day within 70–180 mg/dL (3.9–10.0 mmol/L).
Time Below Range (TBR) Level 1 (Hypoglycemia Alert): Percentage of readings and time within 54–69 mg/dL (3.0–3.8 mmol/L).
TBR Level 2 (Clinically Significant Hypoglycemia): Percentage of readings and time <54 mg/dL (<3.0 mmol/L), requiring immediate clinical attention.
Time Above Range (TAR) Level 1 (Hyperglycemia): Percentage of readings and time within 181–250 mg/dL (10.1–13.9 mmol/L).
TAR Level 2 (Very High Hyperglycemia): Percentage of readings and time >250 mg/dL (>13.9 mmol/L).
Glycemic Management Indicator (GMI): Established by Bergenstal et al. (2018) to replace the older term “estimated A1c (eA1C),” GMI estimates the laboratory HbA1c level expected from a given mean CGM glucose concentration using a regression equation derived from clinical trial populations.
Coefficient of Variation (%CV): The primary metric of within-day and between-day glycemic variability, calculated by dividing the standard deviation (SD) of glucose by the mean glucose. The International Consensus defines stable glycemia as %CV ≤ 36%, whereas values above 36% indicate unstable glycemia with elevated hypoglycemia risk.

International Consensus Targets Across Clinical Populations

The 2019 ATTD International Consensus Report (endorsed by the ADA, EASD, ISPAD, and JDRF) established specific percentage and daily-duration thresholds across distinct patient cohorts. Note that each 1% change in TIR corresponds to approximately 14.4 minutes per day (~15 minutes/day):

Glycemic Metric & Threshold	Standard Adult Type 1 & Type 2 Diabetes Target	Older or High-Risk Adults (Type 1 / Type 2) Target	Pregnancy in Type 1 Diabetes Target (63–140 mg/dL range)
Time in Range (TIR)	>70% (>16 h 48 min/day within 70–180 mg/dL)	>50% (>12 h/day within 70–180 mg/dL)	>70% (>16 h 48 min/day within 63–140 mg/dL [3.5–7.8 mmol/L])
Total TBR (<70 mg/dL / <3.9 mmol/L)	<4% (<58 min/day)	<1% (<15 min/day)	<4% (<58 min/day below 63 mg/dL [3.5 mmol/L])
TBR Level 2 (<54 mg/dL / <3.0 mmol/L)	<1% (<15 min/day)	0% (Avoid entirely)	<1% (<15 min/day below 54 mg/dL)
Total TAR (>180 mg/dL / >10.0 mmol/L)	<25% (<6 h/day)	<50% (<12 h/day)	<25% (<6 h/day above 140 mg/dL [7.8 mmol/L])
TAR Level 2 (>250 mg/dL / >13.9 mmol/L)	<5% (<1 h 12 min/day)	<10% (<2 h 24 min/day)	Included within >140 mg/dL pregnancy TAR threshold

What Is Time in Range Diabetes and How Is It Used in Clinical Research and Healthcare?

In clinical practice, TIR provides actionable feedback that guides insulin basal/bolus titration, automated insulin delivery (AID) pump parameter adjustments, and lifestyle interventions inside chronic care management programs and digital metabolic clinics such as Omada Health. Clinicians prioritize reducing TBR (<70 mg/dL and <54 mg/dL) to target thresholds first before addressing elevated TAR, ensuring that hypoglycemia safety is achieved prior to intensifying antihyperglycemic therapy.

In clinical research, TIR has been validated against microvascular clinical outcomes through retrospective analyses of landmark trials. Notably, Beck et al. (2019, Diabetes Care) analyzed 7-point blood glucose profiles from the Diabetes Control and Complications Trial (DCCT) and demonstrated that for every 10-percentage-point reduction in TIR (70–180 mg/dL), the hazard rate of retinopathy progression increased by 64% and microalbuminuria development increased by 40%. A TIR of 70% empirically corresponds to an HbA1c of approximately 7.0% (53 mmol/mol), and each 10% increase in TIR corresponds to an approximate 0.5% to 0.8% reduction in HbA1c across study populations.

What Standards or Regulatory Requirements Govern Time in Range Diabetes?

For biostatisticians and clinical trialists designing phase 2 and phase 3 diabetes drug or device trials, sampling validity and regulatory device standards are strictly defined:

Minimum CGM Sampling Sufficiency (14 Days / ≥70% Wear Time): The 2019 International Consensus and the 2023 International Consensus on Use of Continuous Glucose Monitoring in Clinical Trials (Battelino et al., Lancet Diabetes & Endocrinology) specify that reliable estimation of 3-month glycemic control requires a minimum of 14 consecutive days of CGM data with at least 70% of possible sensor readings active (approximately 10 days of valid data).
FDA iCGM Special Controls (21 CFR 862.1355): In the United States, the FDA regulates interoperable automated glycemic controller sensors under the Integrated Continuous Glucose Monitoring (iCGM) De Novo classification (21 CFR 862.1355). This regulation establishes strict special controls for point accuracy across glycemic ranges, rate-of-change accuracy, sensor stability over wear duration, and secure data transmission so that CGM outputs can reliably drive automated insulin dosing and serve as regulatory trial endpoints alongside electronic clinical outcome assessment (eCOA) instruments.
CDISC Therapeutic Area User Guide (TAUG-Diabetes): For regulatory submissions to the FDA and EMA, CGM summary metrics (TIR, TBR, TAR, mean glucose, SD, %CV, and GMI) are mapped into standardized Clinical Data Interchange Standards Consortium (CDISC) Study Data Tabulation Model (SDTM) and Analysis Data Model (ADaM) domains.

How Does Time in Range Diabetes Integrate with EHR and Health Informatics Workflows?

Historically, reviewing CGM data required clinicians to log into separate manufacturer cloud portals (such as Dexcom Clarity, Abbott LibreView, or Medtronic CareLink) and manually transcribe TIR and GMI percentages into the EHR progress note. Modern health informatics architectures integrate CGM metrics directly into the EHR using standardized Ambulatory Glucose Profile (AGP) reports and HL7 FHIR resources:

Standardized Ambulatory Glucose Profile (AGP): Developed by the International Diabetes Center (IDC), the single-page AGP report displays the 10 core CGM statistics (including days worn, % time CGM active, mean glucose, GMI, %CV, and the 5-tier stacked bar chart of TIR/TAR/TBR), the 24-hour modal day percentile curves (5th, 25th, 50th/median, 75th, and 95th percentiles), and daily glucose thumbnails.
HL7 FHIR CGM Implementation & EHR Integration: Initiatives led by the Integration of Continuous Glucose Monitoring Data into the Electronic Health Record (iCoDE) consortium and HL7 FHIR Continuous Glucose Monitoring implementation guides standardize how summary CGM metrics and PDF AGP reports are pushed into Epic and Oracle Health. Discrete `Observation` resources annotated with LOINC codes for TIR, GMI, TBR, and %CV allow EHR flowsheet trending, clinical decision support alerts, and remote physiologic monitoring (RPM) billing workflows alongside connected cellular hubs such as Tenovi.

Frequently Asked Questions

What is time in range diabetes and how is it used in clinical research and healthcare?

Time in Range (TIR) is the percentage of time per day that a patient’s continuous glucose monitoring (CGM) readings stay within the target glucose range of 70 to 180 mg/dL (3.9 to 10.0 mmol/L), with a standard clinical goal of >70% (>16 hours and 48 minutes per day) for most adults with type 1 or type 2 diabetes. In clinical care and therapeutic clinical trials, TIR is used alongside Time Below Range (TBR), Time Above Range (TAR), Glycemic Management Indicator (GMI), and coefficient of variation (%CV) to quantify glycemic excursion patterns that HbA1c cannot detect.

What standards or regulatory requirements govern time in range diabetes?

TIR metrics are governed by the 2019 International Consensus on Time in Range (Battelino et al., Diabetes Care) and the American Diabetes Association (ADA) Standards of Care in Diabetes, which require a minimum of 14 consecutive days of CGM wear with at least 70% active sensor data for valid assessment. In regulatory clinical trials, CGM sensors are governed by FDA Integrated Continuous Glucose Monitoring (iCGM) special controls (21 CFR 862.1355) and formatted using CDISC diabetes therapeutic area standards.

How does time in range diabetes integrate with EHR and health informatics workflows?

CGM platforms integrate TIR and Ambulatory Glucose Profile (AGP) metrics into electronic health records (such as Epic and Oracle Health) using the iCoDE (Integration of Continuous Glucose Monitoring Data into the Electronic Health Record) data standard and HL7 FHIR `Observation` and `DiagnosticReport` resources, mapping TIR, TBR, TAR, GMI, and %CV into discrete EHR flowsheets alongside embedded AGP visual reports.

Time in Range (TIR) in Diabetes: Consensus CGM Metrics and Clinical Trial Endpoints