Continuous glucose monitoring (CGM) systems give more information than capillary blood sugar meters. This information is displayed directly on the reader, allowing the user to quickly take proper action and anticipate low blood sugar episodes, and is also used in reports to help better analyze blood sugar trends over a certain period, for example two weeks.
That makes for a lot of information for the user and their healthcare team to keep track of. The time in range and the time spent in hypoglycemia are two important statistics found in these reports.
What is time in range?
Time in range gives a visual representation of the time spent within target blood sugar levels. This data complements hemoglobin A1c (A1c) and helps better assess a patient’s risk of diabetes-related complications. Both time in range goals and A1c goals need to be customized for each patient.
To stay within target blood sugar levels more easily, it is generally recommended to take a moment every two weeks to check time in range values, trends (as needed), and periods of the day where blood sugar levels are the most variable.
Reports also indicate what percentage of time was respectively spent in hypoglycemia and in hyperglycemia, based on personal targets.
Experts came to a consensus on time in range recommendations.
They concluded that people with type 1 diabetes should aim to:
- Spend less than 1 hour per day (4% of time) in hypoglycemia (blood sugar lower than 4 mmol/L)
- Spend less than 6 hours per day (25% of time) in hyperglycemia (blood sugar higher than 10 mmol/L)
This means that time spent in range (between 4,0 and 10,0 mmol/L) should exceed 16.8 hours per day (70% of time). Reaching this threshold often results in an A1c that is very close to 7%.
What are the recommendations for pregnant women?
Target blood sugar levels for pregnant women who have type 1 diabetes are different, as hyperglycemic episodes can have adverse effects on proper fetus development. A blood sugar range between 3.5 and 7.8 mmol/L is recommended. However, time in range recommendations are the same.
A better use of technology
With technology constantly improving and now being covered by more and more private insurers and the RAMQ, the number of CGM system users keeps growing. This means that an ever-growing number of people with type 1 diabetes are getting a clearer picture of their blood sugar levels.
A recent study also concluded that CGM systems are the best device to reduce time spent in hypoglycemia or hyperglycemia, regardless of the method used to inject insulin (pump or needles).
Type 1 diabetes patients and health professionals can therefore work together based on the recommended time in range to identify areas for improvement and establish realistic goals for better blood sugar management.
- Battelino, T., et al. (2019). Clinical targets for continuous glucose monitoring data interpretation: recommendations from the international consensus on time in range. Diabetes Care, 42(8), 1593-1603. doi : 10.2337/dci19-0028
- Šoupal, J., Petruželková, L., Grunberger, G., et al. (2019). Glycemic Outcomes in Adults With T1D Are Impacted More by Continuous Glucose Monitoring Than by Insulin Delivery Method: 3 Years of Follow-Up From the COMISAIR Study. Diabetes Care. doi : 10.2337/dc19-0888