Time‑Above‑Range (TAR) Guidelines for Continuous Glucose Monitoring

Definition and Core Metrics

• TAR represents the proportion of CGM readings (or the absolute time) that exceed the upper glucose target, reported as Level 1 (181–250 mg/dL) and Level 2 (>250 mg/dL). 1
• TAR is one of three core “time‑in‑range” metrics, alongside Time‑in‑Range (70–180 mg/dL) and Time‑Below‑Range (<70 mg/dL). 1
• TAR can be expressed as a percentage of total readings or as absolute hours; for adults with diabetes, a TAR < 25 % corresponds to < 6 hours of hyperglycemia per day. 1

Data Requirements for Reliable TAR Assessment

• A minimum of 14 days of CGM data with ≥ 70 % sensor wear time is required; this duration correlates strongly with 3‑month mean glucose and hyperglycemia metrics. [1][2]

Two‑Level Classification of Hyperglycemia

• Level 1 TAR (moderate hyperglycemia): 181–250 mg/dL (10.1–13.9 mmol/L). 1
• Level 2 TAR (severe hyperglycemia): >250 mg/dL (>13.9 mmol/L). 1

Population‑Specific Clinical Targets

Adults with Type 1 or Type 2 Diabetes

• Target TAR < 25 % of the day (i.e., < 6 hours) above 180 mg/dL. 1

Older or High‑Risk Individuals

• Target TAR < 10 % of the day (i.e., < 2 hours 24 minutes) above 250 mg/dL (Level 2 only). 1

Pregnancy

• Target glucose range is 63–140 mg/dL; TAR is defined as time > 140 mg/dL with stricter goals to reduce fetal risk. 1

Clinical Significance

• Each 5 % increase in TIR (and corresponding decrease in TAR) is linked to clinically meaningful reductions in diabetes‑related complications for both type 1 and type 2 diabetes. 1
• TAR independently predicts TIR alongside TBR and HbA1c, making it essential for treatment optimization. 1
• TAR correlates strongly with mean glucose (r = ‑0.790, p < 0.001), providing real‑time insight into hyperglycemic excursions beyond what HbA1c offers. 2

Integration with Other CGM Metrics

• TAR should be interpreted together with TIR, TBR, and glycemic variability (coefficient of variation, CV). 1
• Primary therapeutic priority is to reduce TBR to < 4 % (< 1 hour/day) for most adults and < 1 % (< 15 minutes/day) for older/high‑risk individuals before aggressively targeting TAR. 1
• After hypoglycemia is controlled, aim for TIR > 70 % and TAR < 25 % in standard‑risk adults. 1
• Glycemic variability should be kept ≤ 36 % when evaluating TAR and TIR, as high variability raises the risk of both hypo‑ and hyperglycemia. 1

Practical Clinical Use

• Visualize TAR using the Ambulatory Glucose Profile (AGP), which aggregates 14 days of CGM data and highlights periods of hyperglycemia needing intervention. [1][2]
• When Level 2 TAR (> 250 mg/dL) is elevated, consider intensifying basal insulin, adding or up‑titrating GLP‑1 receptor agonists or SGLT2 inhibitors, or adjusting prandial insulin coverage. 1

Guideline Recommendations for Time in Range (TIR) in Continuous Glucose Monitoring

Definition and Measurement

• Time in Range (TIR) is defined as the percentage of CGM readings that fall within the target glucose range of 70–180 mg/dL (3.9–10.0 mmol/L) for most adults with diabetes. 3
• TIR is expressed both as a percentage of total readings and as actual daily time (e.g., > 70 % or > 16 h 48 min). 4
• Accurate TIR assessment requires at least 14 days of CGM data with ≥ 70 % sensor wear time. 5

Standard Target Ranges by Population

Adults with Type 1 or Type 2 Diabetes

• Target glucose range: 70–180 mg/dL (3.9–10.0 mmol/L). 6
• Goal TIR: > 70 % of the day (≈ 16 h 48 min). 6
• Time Below Range (TBR) < 70 mg/dL: < 4 % of the day (≈ 1 h). 6
• Time Above Range (TAR) > 180 mg/dL: < 25 % of the day (≈ 6 h). 6

Pregnancy

• Target glucose range: 63–140 mg/dL (3.5–7.8 mmol/L). 7
• Goal TIR: > 70 % of the day (≈ 16 h 48 min). 7

Older or High‑Risk Individuals

• Target glucose range: 70–180 mg/dL (same as standard adult range). 8
• Goal TIR: > 50 % of the day (≈ 12 h). 8
• Time Below Range < 70 mg/dL: < 1 % of the day (≈ 15 min). 8

Clinical Significance

• Every 5 % increase in TIR is linked to clinically meaningful reductions in diabetes‑related complications. 6
• A TIR of 70 % corresponds roughly to an HbA1c of 7 % (53 mmol/mol), whereas a TIR of 50 % aligns with an HbA1c of 8 % (64 mmol/mol). 7

Integration with Other CGM Metrics

• TIR should always be interpreted together with Time Below Range (TBR) and Time Above Range (TAR). 6
• TBR Level 1: 54–69 mg/dL (3.0–3.8 mmol/L). TBR Level 2: < 54 mg/dL (< 3.0 mmol/L), indicating clinically significant hypoglycemia. 4
• TAR Level 1: 181–250 mg/dL (10.1–13.9 mmol/L). TAR Level 2: > 250 mg/dL (> 13.9 mmol/L). 4

Management Priorities

• The primary therapeutic priority is to reduce Time Below Range to the specified target; once hypoglycemia risk is minimized, attention shifts to achieving TIR and TAR goals. 6

Glycemic Variability

• When evaluating TIR, the coefficient of variation (a measure of glycemic variability) should be ≤ 36 %. 4

Time‑Above‑Range (TAR) Metrics and Clinical Targets in Continuous Glucose Monitoring

Definition and Classification

• TAR quantifies the proportion of CGM readings (or absolute time) that exceed the upper glucose target, reported as Level 1 (181–250 mg/dL) and Level 2 (>250 mg/dL). The International Consensus on CGM defines these two tiers to differentiate moderate post‑prandial excursions from sustained severe hyperglycemia. 9

Data Requirements for Reliable Assessment

• A minimum of 14 days of CGM data with ≥70 % sensor wear time is required; this duration correlates strongly with 3‑month mean glucose and hyperglycemia metrics. Longer collection periods (e.g., 4 weeks) are advised for individuals with highly variable glycemic control. 9

Population‑Specific Clinical Targets

Standard‑Risk Adults (Type 1 or Type 2 Diabetes)

• Target TAR < 25 % of the day (equivalent to < 6 hours of glucose > 180 mg/dL). This goal applies to both type 1 and type 2 diabetes in adults without high‑risk features. 9

Older or High‑Risk Individuals

• Target TAR < 10 % of the day (≈ 2 hours 24 minutes) for glucose > 250 mg/dL (Level 2 only). The more stringent limit reflects the priority of avoiding hypoglycemia in frail or high‑risk populations. 9

Pregnancy

• Target glucose range 63–140 mg/dL; TAR is defined as time > 140 mg/dL with stricter goals to reduce fetal risk. 9

Clinical Significance and Outcomes

• Each 5 % increase in Time‑in‑Range (TIR) – and the corresponding decrease in TAR – is associated with clinically meaningful reductions in diabetes‑related complications for both type 1 and type 2 diabetes. 9
• TAR shows a strong inverse correlation with mean glucose (r = ‑0.79, p < 0.001), offering real‑time insight into hyperglycemic excursions beyond what HbA1c provides. 9

Integration with Other CGM Metrics

• TAR should be interpreted together with TIR, Time‑Below‑Range (TBR), and glycemic variability (coefficient of variation, CV). Isolated assessment may miss important safety signals. 9
• Glycemic variability should be maintained ≤ 36 % when evaluating TAR and TIR, as higher variability raises the risk of both hypo‑ and hyperglycemia. 9

Therapeutic Priorities

• First priority: reduce TBR to < 4 % of the day (< 1 hour) for standard‑risk adults and < 1 % (< 15 minutes) for older/high‑risk individuals before aggressively targeting TAR. 9
• After hypoglycemia is controlled, aim for TIR > 70 % and TAR < 25 % in standard‑risk adults. 9
• When Level 2 TAR (> 250 mg/dL) is elevated, intensify basal insulin, add or up‑titrate GLP‑1 receptor agonists or SGLT2 inhibitors, or adjust prandial insulin coverage. 9

Practical Clinical Application

• Visualize TAR using the Ambulatory Glucose Profile (AGP), which aggregates ≥ 14 days of CGM data and highlights periods of hyperglycemia requiring intervention. 9
• CGM‑guided lifestyle interventions (diet and activity) can reduce TAR from roughly 50 % at baseline to 20–30 % within 3–6 months, even without medication changes. 9