The Time in Range (TIR) is a concept based the percentage of time a person with diabetes spends with their sensor glucose (SG) levels in a particular target range. The emergence of continuous glucose monitoring is underpinning improvements in glycaemic control and the development of this concept of time in range (TIR). TIR has emerged as a key metric for assessing glycemic control in addition to HbA1c. It is recommended to aim for SG levels between 3.9-10.0 mmol/L (70–180 mg/dl) while reducing time spent in hypoglycaemia. Based on the current evidence and a consensus a TIR of >70% is recommended for most individuals who have type 1 and type 2 diabetes.
TIR is considered to be a metric of high value for clinical care as it is a number that can be actioned and can be visibly used for education and as a measure to monitor changes. While the HbA1c is valuable as an average measure over the previous 2-3 months, it can not measure the variability of glycaemic control and does not provide information on hypoglycaemia and hyperglycemia. Iron deficiency and pregnancy can also affect HbA1c measurements.
Definitions:
Time in Range (TIR): the percentage of readings and time per day within the target glucose range that is defined as 3.9–10.0 mmol/l (70–180 mg/dl).
Time below range (TBR): the time spent below the target of 3.9 mmol/l (70 mg/dl).
Time above range (TAR): the time spent above target of 10.0 mmol/l (180 mg/dl)
2019 International Consensus on Time in Range:
An international working group established the series of target glucose ranges and recommendations for time spent within these ranges that is consistent with optimal glycaemic control:
From the International Consensus Report, Diabetes Care, August 2019
The international consensus report has been endorsed by the American Diabetes Association, American Association of Clinical Endocrinologists, American Association of Diabetes Educators, European Association for the Study of Diabetes, Foundation of European Nurses in Diabetes, International Society for Pediatric and Adolescent Diabetes, JDRF, and Pediatric Endocrine Society.
Time in Range and Diabetes Complications:
Strong correlations between TIR and diabetes-related complications have been reported in a number of studies, especially on retinopathy and nephropathy.
Time in Range and Diabetic Foot Complications:
Li et al’s (2022) short term retrospective analysis of those who underwent a toe amputation showed that patients in the TIR < 70% had a higher rate of re-amputation, and a higher rate of postoperative infection. A multivariate analysis revealed that smoking, lower extremity arterial disease and TIR < 70% were risk factors for a re-amputation.
External Links:
Time in range and diabetic foot amputation (Podiatry Arena)
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