Time in Range
Last Updated: August 7, 2019
“Time in Range” (TIR) is the percentage of time that a person spends with their blood glucose levels in a target range. The range will vary depending on the person, but general guidelines suggest starting with a range of 70 to 180 mg/dl. (Over time, some people decide to aim for a tighter range, such as 70 to 140 mg/dl.)
Want more information like this?
In a single number, time-in-range captures a lot about how blood glucose levels might vary throughout a day or over time. The example graphics below show various levels of time-in-range, from 0% to 100%:
Time-in-range can also be understood as “hours per day” spent in-range. For example, 50% time-in-range (70-180 mg/dl) means 12 hours per day spent in-range.
TIR goes Beyond A1C in representing blood glucose levels because it captures variation – the highs, lows, and in-range values that characterize life with diabetes. By contrast, A1C is a measure of average blood sugar over a two-to-three-month period; it cannot capture time spent in various blood glucose ranges. To illustrate the limitations of A1C and the advantages of time-in-range, see the graphics below. These three examples show three different people – all with the same average blood glucose (154 mg/dl) and the same A1C (7%). However, the highs, lows, and in-range blood glucose values are markedly different: the first person has a rollercoaster of dangerous highs and lows, the second has moderate variability and fewer highs and lows, and the third person has little variability with all time spent in-range.
People living with diabetes experience different energy levels, moods, and overall quality of life when they are “in-range” vs. “out-of-range.” Time-in-range can capture these differences in a way A1C cannot.
Because time-in-range can be measured at home on a daily basis or weekly basis (see below), it has a huge advantage over A1C: understanding what behaviors and choices prompt more time-in-range (Bright Spots), what drives blood glucose out-of-range (Landmines), and where/when changes can be made (e.g., time of day). Thinking about blood glucose in terms of time-in-range offers a more nuanced, cause-and-effect understanding of diabetes than A1C. For instance, how do different foods affect your time-in-range? How does walking after meals affect your time-in-range? A1C cannot reveal these relationships.
On a longer time horizon, early studies suggest time-in-range is just as good a predictor of long-term diabetes complications (e.g., Diabetes Care 2019, Diabetes Care 2018). In a re-analysis of a landmark study (DCCT), researchers found a strong relationship between different levels of time-in-range and diabetes complications: eye disease (retinopathy) and kidney disease (microalbuminuria). As time-in-range increased, complications decreased.
Some researchers believe time-in-range may emerge as a better predictor of complications, since it is a direct measure of glucose in the blood vessels – i.e., what actually does damage to the body. By contrast, A1C is an indirect measure of blood glucose, since it is dependent on red blood cell turnover (and that varies between people quite a bit; read more here.)
On average, a time-in-range (70-180 mg/dl) of 70% corresponds with an A1C of approximately 7%; a time-in-range of 50% corresponds to an A1C of approximately 8%.
Time-in-range goals are different for every person and may depend on medication, type of diabetes, diet (especially carb intake), age, health, and risk of hypoglycemia. In general, people with diabetes should aim to spend as much time in-range as possible, taking care to avoid low blood sugars and too much burden. Experts emphasize that even a 5% change in time-in-range – for example, going from 60% to 65% – is meaningful, as that translates to one more hour per day spent in-range.
In studies and large real-world data sets, time-in-range is typically around 50%-60% in the average person with diabetes. Recently, researchers published goals for time-in-range, above-range, and below-range for various groups of people with diabetes.
For people with type 1 or type 2 diabetes, experts recommend aiming for:
At least 70% of the day in 70-180mg/dl
Less than 4% of the day below 70mg/dl
Minimize time each day above 180mg/dl
For people with gestational diabetes, experts recommend aiming for:
At least 85% of the day in 63-140mg/dl
Less than 4% of the day below 63mg/dl
Less than 10% of the day above 140mg/dl
For people with medically “frail” diabetes, experts recommend aiming for:
At least 50% of the day in 70-180mg/dl
Less than 1% of the day below 70mg/dl
Less than 10% of the day above 250mg/dl
For people who are pregnant and have type 1 diabetes, experts recommend aiming for:
At least 70% of the day in 63-140mg/dl
Less than 4% of the day below 63mg/dl
Less than 25% of the day above 140mg/dl
What is time-in-range in people without diabetes? A recent study put CGM on people without diabetes for 10 days, finding 97% time-in-tight-range (70-140 mg/dl), with blood glucose levels averaging 99 mg/dl and showing little variation.
Consistent, in-range blood glucose levels are sometimes called “flat, narrow, in-range” (FNIR). This is one way to think about “ideal” blood sugars: high time-in-range and flat glucose levels with few ups and downs. People with type 1 or type 2 diabetes can strive for FNIR. On a day with FNIR levels, ask: What made that possible? How can I have more days like that?
To determine your TIR, you should use at least 14 days’ worth of blood glucose data.
TIR is most accurately measured using a continuous glucose meter (CGM), although a blood glucose meter (BGM) can also be used.
CGM provides a constant stream of information about your blood sugar – every five minutes – which means that you have a full picture of precisely how many hours of the day you spent in your target range. This includes overnight and after meals, which are usually missed with fingersticks. If you don’t have access to your own personal real-time CGM, ask your healthcare provider about professional CGM.
If you have CGM, TIR is calculated automatically in the software/app that comes with your device: Dexcom Clarity Mobile app and Clarity on the computer; FreeStyle LibreLink mobile app and LibreView on the web; Medtronic’s CareLink on the web and Sugar.IQ mobile app; and Senseonics Eversense DMS.
With a BGM, the more fingersticks you take throughout the day, the better the picture you’ll get of your TIR. Make sure to get readings over at least two weeks, ideally with some fingersticks taken after meals and overnight.
If you are using BGM data, TIR is the percentage of your data points that fall in your range over a period of time. In the graphic on the right, TIR would be 50% - half the readings are in-range and half are out-of-range. You can most easily calculate TIR with an app, by entering or uploading your BGM fingerstick data. Bluetooth-enabled meters come with paired apps, including Accu-Chek Connect, Contour Diabetes, One Drop, OneTouch Reveal, mySugr.
If you don’t have a BGM with Bluetooth, you can take 14 days of fingerstick data and calculate TIR manually using this equation:
Read Bright Spots & Landmines by diaTribe Senior Editor Adam Brown – it is filled with hundreds of tips for improving time-in-range.
Time-in-Range: What’s an Achievable Goal with Diabetes? – Adam shares five key tips for spending more time-in-range
Wear CGM or check blood glucose more often, using the data to understand patterns
Minimize the biggest glucose disturbances and sources of error – for Adam, that’s too many carbohydrates at one time
Make course corrections when out-of-range blood sugars occur
Identify and replicate Bright Spots – when I have a day with lots of time-in-range, what happened? How can I replicate those decisions?
Build routines to minimize Landmines – when I see less time-in-range, what choices drove that? How can I avoid those decisions next time?
Have a question about time-in-range? Is this article missing something? Let us know!
CGM and Time-in-Range: What Do Diabetes Experts Think About Goals? published 12/20/17
Going Beyond A1C – One Outcome Can’t Do It All published 8/25/16
What's a "Normal" A1C? When is it Misleading? published 10/23/17
Validation of Time in Range as an Outcome Measure for Diabetes Clinical Trials in Diabetes Care, March 2019
Association of Time in Range, as Assessed by Continuous Glucose Monitoring, With Diabetic Retinopathy in Type 2 Diabetes in Diabetes Care, November 2018
The Fallacy of Average: How Using HbA1C Alone to Assess Glycemic Control Can Be Misleading in Diabetes Care, August 2017
The Relationship of Hemoglobin A1C to Time-in-Range in Patients with Diabetes in Diabetes Technology & Therapuetics, February 2019
Click here for a full list of resources on time in range.