Abstract: The invention provides a blood sugar measuring device to measure blood sugar either non-invasively or with only slight invasiveness which is capable of better measurement accuracy. The device receives as input measured data related to blood sugar level such as patient mealtime and how much food he had, or if he had an insulin injection and adjusts the measured blood sugar value based on the data which are previously input based on the above measured data. The device also may include a retry indicator which retries the measurement (or directs the user to retry the measurement) if the measurement result is out of a proper or predetermined range.