On average, the sensor reading differs from a blood sugar test by approximately 10%. The difference is the greater the faster the sugar level changes. Furthermore, the sensor reading lags 10–15 minutes behind the fingertip blood sugar test. The reader uses arrows to show the direction of the change in blood sugar, either up or down, as well as the speed of change, which makes the result easier to assess.
If the sensor system needs calibrating, it is of the utmost importance to perform the calibration measurement carefully so as to ensure reliable results. The calibration is performed when the blood sugar level is even in the morning or before a meal.
If the glucose level changes rapidly, it may be necessary to double-check the result using a fingertip blood test before making any decisions regarding the treatment. Especially if the result is low, it should be verified with a fingertip blood test.
The operation of the sensor may be affected by temperature changes, the body’s fluid balance or liquid circulation in the tissue at the sensor’s location.