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Reliability of blood sugar measurement results

At the time of measurement, the result may be affected by a host of disturbing factors. Reducing or removing them ensures as reliable a result as possible.

The technology used for checking the blood sugar level as well as the way the equipment is stored and handled have an effect on the reliability of the results. You should carefully familiarise yourself with the user instructions of your meter and practice using it with your nurse.

If the result shown by the meter seems unreliable considering the situation and the way you feel, you should check your blood sugar again immediately using reliable technology. At the same time, try to think what could have possibly gone wrong.

The blood sugar result indicated by the meter means the glucose content of your blood. Its unit is mmol/l (millimoles per litre). Depending on the meter, the range is 0.6–33.3 mmol/l. The amount of blood required for the test strip is 0.3–0.6 microlitres.

The results achieved with meters and test strips are required to be reliable in accordance with the international (ISO15197:2013) standard. In practice, the accuracy of an instant meter is approximately 10 %. Hence, for a blood sugar value of 10 mmol/l, the correct result is 9.0–11.0. For a value of 5 mmol/l, the result is 4.5–5.5. This is accurate enough for the purpose of monitoring the success of diabetes therapy. The accuracy is especially important if the insulin dose is based on the result.

More than the meter itself, major test inaccuracies may be down to the person performing the check or errors in performing it. If the blood sugar result does not correspond with the actual level or sensations despite a control check, you should take the meter to the treatment centre to make sure that it works properly.

When it comes to technical issues related to blood glucose meters, you can also contact the device manufacturer or importer’s product support. Remember to quote the serial number of the meter as well as the lot number of the test strip tub.

Factors that may affect the reliability of the blood sugar result:

  • The skin in the injection site is dirty

  • The injection site is covered in disinfectant or hand lotion

  • Squeezing the fingertip

  • The drop of blood is too small

  • Cold skin or poor peripheral circulation

  • The test strips have been exposed to dirt, humidity, dust, heat or cold

  • The lid of the test strip lid has been left open or the strips have expired

  • The blood glucose meter is too cold

  • There is dirt or humidity inside the strip slot of the blood glucose meter

  • The blood glucose meter is damaged or its battery is weak

Some medical conditions affecting the composition of blood or oxygen therapy may have an effect on individual results, which must be taken into account when selecting a blood glucose meter.

Updated 30.9.2023