What Is Time in Range? The T1D Metric That Changed Everything
Quick answer: Time in Range (TIR) measures the percentage of time your blood glucose stays between 70–180 mg/dL. The ADA recommends at least 70% TIR for most adults with Type 1 Diabetes. Higher TIR correlates with lower HbA1c and fewer complications.
For decades, HbA1c was the only number that mattered in diabetes care. One blood test, every three months, telling you your average glucose over the past 90 days. Clean, simple, and — as it turns out — dangerously incomplete.
Time in Range (TIR) changed that. It is now considered by the ADA, EASD, and leading endocrinologists worldwide as the single most important metric for day-to-day T1D management. Here is everything you need to know about it.
What Exactly Is Time in Range?
Time in Range measures the percentage of time your glucose level stays within the target zone. For most people with Type 1 Diabetes, that zone is 70 to 180 mg/dL (3.9 to 10.0 mmol/L).
If your CGM data shows you spent 17 hours of the last 24 hours between 70 and 180 mg/dL, your TIR is about 71%. The Latest ADA/EASD/ISPAD target for most adults with T1D is at least 70% TIR — meaning no more than 7.2 hours per day outside the safe zone [1] [2].
Why Not Just Use HbA1c?
HbA1c tells you the average glucose over three months. The problem is that averages hide volatility. Two people can have identical HbA1c readings of 7.0% while living completely different glucose lives.
Person A might spend 80% of their time in range, with occasional mild highs. Person B might spend equal time severely hypoglycemic (crashing to 45 mg/dL overnight) and severely hyperglycemic (spiking to 280 mg/dL after meals). Their average HbA1c would be similar, but their health trajectories are wildly different. HbA1c cannot see this. TIR can.
Research has consistently shown that higher TIR correlates with lower rates of diabetic retinopathy, nephropathy, and cardiovascular complications — independent of HbA1c [4]. It is not a replacement for HbA1c, but it adds a critical dimension that HbA1c alone cannot provide [3].
The Latest ADA/EASD/ISPAD TIR Targets
The Latest ADA/EASD/ISPAD Standards of Medical Care set clear TIR goals for different patient populations:
- Most adults with T1D: Greater than or equal to 70% TIR (70–180 mg/dL), with less than 4% below 70 mg/dL
- High-risk individuals (older adults, hypoglycemia unawareness): Greater than or equal to 50% TIR, with less than 1% below 70 mg/dL
- Pregnant women with T1D: Greater than or equal to 70% within the tighter 63–140 mg/dL range, with less than 4% below 63 mg/dL
The 4% threshold below 70 mg/dL is particularly important. That represents about 58 minutes per day below the hypoglycemia threshold — a number that sounds small but correlates with significant risk of severe hypoglycemia events.
Time Below Range and Time Above Range
TIR is actually one piece of a three-part picture. The full framework includes:
- Time in Range (TIR): Percentage between 70 and 180 mg/dL. Target: ≥70%
- Time Below Range (TBR): Percentage below 70 mg/dL. Target: less than 4%. Below 54 mg/dL (severe hypo): less than 1%
- Time Above Range (TAR): Percentage above 180 mg/dL. Target: less than 25%. Above 250 mg/dL (very high): less than 5%
These three numbers should add up to 100%. Improving TIR means reducing both TBR and TAR — but not at the expense of each other. Aggressively correcting hyperglycemia can push someone into dangerous hypoglycemia, worsening TBR even as TAR improves.
How CGM Made TIR Possible
You cannot calculate TIR from finger-stick blood glucose checks — you would need to check every 5 minutes for 24 hours. This is why TIR only became clinically practical with the widespread adoption of Continuous Glucose Monitors (CGMs).
A modern CGM checks glucose every 5 minutes — 288 readings per day. At the end of the day, your app can show you exactly what percentage of those readings fell in each zone. This data density is what makes TIR meaningful. The standard recommendation is to use at least 14 days of CGM data to calculate a reliable TIR estimate.
TIR in the FlightGlucose Simulation
FlightGlucose uses TIR as its primary scoring metric. After every scenario, you see your Time in Range percentage alongside the clinical target for that patient. This is intentional — we want players to experience what it feels like to manage glucose with a TIR goal in mind, not just a single target number.
The green safe zone in the game (the altitude band where the plane flies safely) represents exactly the 70–180 mg/dL TIR range. When your plane flies in that band, you are earning TIR. When it climbs or drops, you are losing it.
See your Time in Range score in real time — play a scenario now
Play Free to Learn →References
- Battelino T, Danne T, Bergenstal RM, et al. Clinical targets for continuous glucose monitoring data interpretation: recommendations from the international consensus on time in range. Diabetes Care. 2019;42(8):1593-1603. doi:10.2337/dci19-0028 [Link]
- American Diabetes Association. 6. Glycemic Goals and Hypoglycemia: Standards of Care in Diabetes—2024. Diabetes Care. 2024;47(Suppl 1):S111-S125. doi:10.2337/dc24-S006 [Link]
- Beck RW, Connor CG, Mullen DM, et al. The fallacy of average: how using HbA1c alone to assess glycemic control can be misleading. Diabetes Care. 2017;40(8):994-999. doi:10.2337/dc17-0399 [Link]
- Lu J, Ma X, Zhou J, et al. Association of Time in Range, as Assessed by Continuous Glucose Monitoring, With Diabetic Retinopathy in Type 2 Diabetes. Diabetes Care. 2018;41(11):2370-2376. doi:10.2337/dc18-1131 [Link]