Time in range is the percentage of time your blood sugar level is within a ‘target’ range. It is decided by your healthcare team and could be anywhere from 3.9mmol/l to 10mmol/l. It is not a replacement for HbA1c, another way to measure blood sugar levels.
Being within an ‘ideal’ or ‘target’ range over time means you are less likely to develop complications from high blood sugar levels.
Time in range and flash glucose monitor or CGM
If you use a flash glucose monitor (Freestyle Libre) or continuous glucose monitor (CGM), which shed lights on your blood sugar levels 24 hours a day, it tells you what your time in range is every day.
If time in range isn’t as high as you’d like, you and your healthcare team can see from the graphs on your device when your blood sugar started to go up during the day and look for reasons why so you can try something different.
For example, you may spot low-level hypos overnight that don’t wake you up. These can push your blood sugar levels up during the day. So if this is a regular pattern, it may help to reduce your overnight insulin.
Time in range v HbA1c
The most common way to measure ‘safe’ ranges in blood sugar levels is your HbA1c your average blood sugar levels for the last two to three months. It’s done with a blood test (not the normal finger prick test you’d usually do).
If you have diabetes, an ideal HbA1c level is 48mmol/mol (6.5%) or below. That roughly equates to a time in range of 80% of the time.
During the pandemic, when people couldn’t see their healthcare professionals and have their HbA1c blood tests done, time in range was a different way for them to keep track of how people were doing who had a CGM or flash glucose monitor. That’s because the results of your blood sugar readings can be shared automatically with your healthcare team.
Although HbA1c doesn’t give you an understanding of what your blood sugar levels are doing at all times, it’s an effective way of measuring your risk of getting diabetes complications from high blood sugar levels.
So using time in range together with HbA1c can be an effective way for your healthcare team to review your diabetes care to help you reduce your risk of long-term health problems.
