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Two Different Blood Sugar Readings Within Seconds: Why?

In this article, we will take a close look at the factors that can cause two different blood sugar readings within seconds. We will discuss the role of cleanliness, the difference between the first and second blood drops, the impact of interfering substances, and the accuracy of the glucose sensor itself.

Jakub Gwiazdecki

Author - Jakub Gwiazdecki

Fifth year medical student at the Medical Faculty of Comenius University in Bratislava.

Jakub used MediSearch to find sources for this blog.
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Is it possible to get two different blood sugar readings within seconds?

Yes, it is possible to get two different blood sugar readings within seconds.

Several factors can cause two different blood sugar readings within seconds. The primary factor that can influence two blood sugar readings within seconds is the cleanliness of the hands.

Testing sugar levels without washing hands can lead to contamination of the blood samples. As a result, the glucose readings of the first and the second drops of blood can differ by more than 10% [1].

However, even after washing hands, the first and second drops of blood can give different results.

Usually, measurements of glucose concentration lower than 10 mmol/l is more exact for the first blood drop. The second blood sample is more precise for blood sugar levels higher than 10 mmol/l [2].

Other factors that can interfere with blood sugar readings and lead to differences in the two measurements are interfering substances, such as vitamin C and uric acid. Different concentrations of these substances in each blood drop can interfere with the results [3].

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Lastly, the accuracy of the glucose sensor itself can cause different readings within seconds. The accuracy can be affected by dirt or by a malfunction of the device [4].

How to prevent two different blood sugar readings within seconds?

It is difficult to prevent two different blood sugar readings within seconds. However, it is possible to minimize the difference. Here are a few things to remember.

  • Always wash your hands before measurement.
  • Remember to check your measuring device for dirt and malfunction.
  • Don’t take high doses of vitamin C, paracetamol, furosemide, or propranolol. These substances can interfere with the reading.

Remember that even adherence to all possible rules cannot prevent slight differences in the results.

Which blood glucose testing method is the most accurate?

The Diabetes Technology Society tested 18 popular blood glucose meters. Out of them, only six brands passed their accuracy test.

The brands with the highest accuracy include:

  • Contour Next, Bayer (100%),
  • Accu-Chek Aviva Plus, Roche (98%),
  • Walmart ReliOn Confirm (Micro), Arkray (97%),
  • CVS/pharmacy Advanced, Agamatrix (97%),
  • FreeStyle Lite, Abbott (96%),
  • Accu-Chek SmartView, Roche (95%) [5, 6, 7, 8, 9].

Should I see a doctor when I have two different blood sugar readings within seconds?

Generally, you do not need to see a doctor if you have two different blood sugar readings within seconds.

An insignificant difference between two measurements can happen and is nothing worrying.

However, when both the blood sugar results are above 300 mg/dL (16.7 mmol/L), you should immediately look for medical attention [10].

Also, when the values are constantly above 240 mg/dL (13.3 mmol/L), you should make an appointment with your doctor.

When the difference between the blood sugar results is significant, you can repeat the test. This time, make sure to adhere to all possible rules of measurement.

If this variation is permanent, you may want to try a new measuring device.

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