We know the A1C test provides average blood glucose levels over a 3-month period, but what if I told you that time in range (TIR) provides a more detailed picture?
What is Time in Range?
Time in range is a measure of the % of time glucose levels are in range, which is usually between 70 and 180 mg/dL.
The ADA recommends aiming to have a TIR of at least 70% of readings, which means at least 17 hours of a 24-hour day of not being high or low. However, discuss what your range should be with your healthcare provider because other factors influence what the target should be, such as your age, whether you have cardiovascular disease, hypoglycemia unawareness, are pregnant, etc.
TIR vs A1C
Do we really need to monitor our time in range if we have A1C tests? The answer is yes, as time in range is more like a weekly report, whereas A1C provides monthly summaries.
To illustrate, consider two individuals with an A1C of 7%. The first person has highs and lows throughout the week, while the second person has more stable blood sugars, with few highs and lows, and spends most of the week in range. Their blood sugar average is around 154. Therefore, if you are only looking at the A1C of 7%, it seems both have their blood sugar under control, which can be misleading.
In short, TIR is helpful because the A1C test does not display the blood sugar variations and fluctuations over days and weeks, even though both individuals have an A1C of 7%.
The first person can now use the TIR data to see how their blood sugar responds to food, exercise, stress, medication, etc.
You can use TIR the same way to review trends, which are the general direction in which your blood glucose levels develop. Having an off day with erratic blood sugar levels is normal, but spotting trends will help you make necessary changes. As I always say, be a diabetic detective. For example, if your blood sugar has been high all week after dinner, you may need to adjust your medication, change your diet, etc. In contrast, if you’re constantly going low at night, you may need to cut back on insulin, eat more carbs before bedtime, exercise earlier in the day, etc. Also, if you wear a CGM, you may need to adjust the insulin dose, timing, the high and low alarm settings, etc. Use the TIR data to identify which time of day you are often out of range. Then make one change at a time and see if Time in Range improves.
How to measure TIR
The best way to measure time in range is by using a continuous glucose monitor (CGM) with a TIR feature. But what if you don’t wear a CGM? Don’t worry, you can use a blood glucose meter. The first method is to calculate your TIR by performing frequent blood testing over 14 days and testing before and after meals, overnight, and in the morning. Then you enter or upload the data into an app.
The second alternate method is to calculate the TIR manually by using the equation below and taking 14 days of blood glucose data.
(from BREAKTHROUGHT1D CANADA)
When TIR Increases, Diabetes Complications Decrease
Another reason to improve your TIR, besides better control, is that it can decrease complications. Researchers discovered a high correlation between different time in range levels and diabetes complications, including kidney disease and eye disease (retinopathy), in a re-analysis of a landmark study (DCCT). Complications decreased with more extended time in range (https://diatribe.org/diabetes-management/time-range). Also, as TIR increases, A1C usually decreases.
How to Increase/Improve Your Time in Range
Here are ways to improve your time in range, but remember that this is not medical advice, and if you are constantly out of range, discuss your plan of action with your doctor or endocrinologist. Actions you can take include:
- Drinking enough water
- Getting enough sleep
- Eating a healthy diet
- Reducing stress
- Being active
- Adjusting the timing and/or dosage of medication if necessary
- Reviewing the 42 factors that can affect blood glucose from diaTribe
Conclusion
Time in range is not a replacement for A1C tests, and both are useful in helping you and your healthcare provider get a better picture of your diabetes control. In summary, an A1C is a blood sugar average over several months, whereas TIR can reveal daily and weekly trends. A1C tests do not reveal the frequent blood sugar fluctuations over a smaller period, so use both to spot trends, make adjustments, and improve blood sugar control.
Quote
“Make the maintenance of your diabetes fit your construct. If you are forgetful, set alarms to remind you of what you must do. Know that life is our medicine, not just the shots or pills we take. Exercise, food, sleep, and management of stress are also our medicine. Take all your medicine.” Dorian Gregory