Calculation of the hyperglycaemic index (HGI). All measured glucose values (black dots) and their corresponding sampling times are taken into account. The average over time is calculated for the area (shaded) under the glucose curve for hyperglycaemic values only. The normal glucose range is indicated by the hatched area, with 6.0 mmol/l (dotted line) the cutoff. HGI is the shaded area divided by the total length of stay. In this case HGI is 0.73 mmol/l, as indicated by the dashed line. Note that normal or hypoglycaemic measurements do not affect HGI, and thus they do not falsely lower this index.