Key metrics for CGM data analysis and reporting
| CGM metric | Short description | Reference |
| TIR | Measures the percentage of time spent in consensus target glucose range 70–180 mg/dL (3.9–10.0 mmol/L) | Battelino et al 25 |
| TBR | Measures the percentage of time spent with glucose <70 mg/dL (<3.9 mmol/L), including readings <54 mg/dL (<3.0 mmol/L) | Battelino et al 25 |
| TAR | Measures the percentage of time spent with >180 mg/dL (>10.0 mmol/L), including readings >250 mg/dL (>13.9 mmol/L) | Battelino et al 25 |
| eA1C | A linear transformation of the mean glucose value, meant to estimate the HbA1C blood test. Calculated by the following formula: (46.7+mean (glucose))/28.7 | Nathan et al 26 |
| J_index | This index was designed to stress the importance of the two major glycaemia components: the mean level and the variability of glycaemia. Calculated by the following formula: 0.001×(mean (Glucose)+SD(Glucose))2 | Wójcicki27 |
| MAGE | Mean amplitude of glycaemic excursions (MAGE), an index for glycaemic variability. This index is focused on the amplitude of blood glucose changes, and as such it takes into account only changes in the blood glucose (either upward or downward) that are large enough to be considered significant responses—exceeding one SD of the blood glucose for the same 24 hours period. | Service et al 28 |
| MODD | Mean difference between glucose values obtained at the same time of day (MODD). This is a measure of glycaemic variability that is calculated by taking the mean of the absolute differences between glucose values measured at the same time, a day apart. | Service et al 28 |
| CV | A measure of dynamic glucose variability expressed as percentage CV and calculated as 100 × (SD divided by mean glucose); CV is correlated with time below range | Rodbard29 |
| HBGI | High blood glucose index (HBGI) is a measure used to assess the variability and magnitude of high blood glucose levels in individuals with diabetes. It provides a quantitative indication of how often and how severely blood glucose levels exceed the target range. Prior to calculation, the blood glucose levels are transformed using a nonlinear transformation to create a symmetric distribution around the ‘clinical centre’ and create equal-sized intervals for hyperglycaemic and hypoglycaemic ranges (without this transformation the range of hyperglycaemia is much larger than the range for hypoglycaemia). | Kovatchev et al 30 |
| LBGI | Low blood glucose index (LBGI) is a numerical metric used to assess the extent of low blood glucose levels or hypoglycaemia in individuals with diabetes. It quantifies the risk and severity of hypoglycaemic events. | Kovatchev et al 30 |
CGM, continuous glucose monitoring; CV, coefficient of variation; eA1C, estimated A1C; HbA1C, haemoglobin A1c; TAR, time above range; TBR, time below range; TIR, time in range.