The method involves reading out blood glucose and post-prandial blood glucose measurements provided with relative or absolute time mark and labelled as pre-prandial from memory of measuring instrument. The chronological sequence of the blood glucose measurements labelled as pre-prandial and post-prandial blood glucose measurements that correspond to pre-prandial blood glucose measurements are determined by applying time selection criterion. The difference between pre-prandial and post-prandial blood glucose measurements is determined and value is displayed. Independent claims are included for the following: (1) system for determining difference between pre-prandial and post-prandial blood glucose measurement and (2) computer program product for determining difference between pre-prandial and post-prandial blood glucose measurement.
