Man checking blood sugar with glucometer while wondering what can cause false high blood sugar readings

What Can Cause False High Blood Sugar Readings?

Written on August 7, 2023 by Lori Mulligan, MPH. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

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For anyone living with diabetes, the key to avoiding diabetes-related complications such as heart disease, nerve damage, eye problems, kidney disease, and the dangerous onset of hypoglycemia, is to proactively manage blood sugar levels.

When used correctly, blood glucose monitors—small devices that measure and display your blood sugar level—are usually accurate. But occasionally they may be incorrect.

You may be wondering what can cause false high blood sugar readings. Consider these factors that affect meter accuracy and the steps to resolve or prevent the problem.

Test Strip Problems

Throw out damaged or outdated test strips. Store strips in their sealed container. Keep them away from moisture and humidity. Be sure the strips are meant for your specific glucose meter.

Extreme Temperatures

Keep your glucose meter and test strips at room temperature.

Alcohol, Dirt, or Other Substances on Your Skin

Wash and dry your hands and the testing site thoroughly with soap and water before pricking your skin. Don't use hand sanitizer before testing. If using alcohol wipes, let the site completely dry prior to pricking.

Monitor Problems

Fully insert the test strip into the monitor. Replace the monitor batteries as needed. Replace the monitor every 4 to 5 years.

Not Enough Blood Applied to the Test Strip

Touch a generous drop of blood to the test strip. Don't add more blood to the test strip after the first drop is applied.

Testing Site Location

If you're using a testing site other than your fingertip and you think the reading is wrong, test again using blood from a fingertip. Blood samples from alternate sites aren't as accurate as fingertip samples when your blood sugar level is rising or falling

The Amount of Red Blood Cells in Your Blood

If you are dehydrated or your red blood cell count is low (anemia), your test results may be less accurate.[1]

Everlywell HbA1c Test CTA graphic

Inadequate Education of Patients and Diabetes team

To provide reliable blood glucose results, even blood glucose systems with high analytical performance require correct handling and appropriate measurement conditions. Inadequate education has been identified as a leading cause of bad self-monitoring blood glucose (SMBG) performance. Thus, patients need appropriate education in the correct performance of SMBG as well as for handling and storage of test strips. Education must also include careful interpretation of blood glucose readings since blind trust in exceptional results may produce wrong and even dangerous treatment decisions.[2]

Meter Not Calibrated

Blood glucose meters sometimes lose their accuracy without any obvious signs, so you should calibrate your meter regularly.

To calibrate your meter, you need to perform a control solution test. The solution sometimes comes with your meter. If it doesn’t, get in touch with the manufacturer: they’ll usually be happy to provide a control solution for free. To find out exactly how to calibrate your specific meter, consult the instruction manual.[3]

Risks of Glucose Dehydrogenase Pyrroloquinoline Quinone (GDH-PQQ) Enzyme/Indicator Test Method.

Certain saccharides can falsely elevate the results obtained from point-of-care (POC) glucose meters using the glucose dehydrogenase pyrroloquinoline quinone (GDH-PQQ) enzyme/indicator test method.

The most common methods offered by the medical manufacturers and FDA to prevent falsely elevated blood glucose levels include the following [4]:

  • Labeling affected POC glucose meters to alert users not to use that meter for patients receiving icodextrin (Extraneal) or other solutions containing maltose, galactose, or xylose
  • Educating staff and at-risk patients about the problem and becoming familiar with the enzymatic test method used by the relative POC glucose meter.
  • Instructing staff and at-risk patients to use an alternative POC glucose meter not based on the GHD-PQQ test method during therapy with interfering drugs

In addition to the methods described above to prevent falsely elevated blood glucose levels, clinical analysts suggest that providers also consider the following:

  • Identify patients who have received or will be receiving icodextrin-, xylose-, maltose-, or galactose-containing agents.
  • Make sure POC glucose meters not based on the GHD-PQQ method are available in areas with high-risk patients or only using laboratory glucose testing for high-risk patients.
  • Recheck suspected hypoglycemia with a laboratory glucose test or a POC meter not based on the GHD-PQQ method if POC blood glucose results are inconsistent with a clinical suspicion of hypoglycemia.

Blood Glucose Levels Move Up and Down

Your results can vary because of natural changes in your blood glucose level. For example, your blood glucose level moves up and down when you eat or exercise. Sickness and stress also can affect your blood glucose test results.[5]

How Everlywell Can Help

Everlywell offers an at-home HbA1c test (with sample collection at home and sample testing in a lab) that could serve as a periodic complement to your more frequent blood glucose monitoring to help you manage your diabetes.

Best Time for HbA1c Test

How Much Can I Lower My A1c in a Month?

What Happens When A1c Is Too High?


  1. Blood glucose monitors: What factors affect accuracy? Mayo Clinic. URL. March 15, 2022. Accessed on July 23, 2023
  2. Erbach M, Frechmann G, Hinzmann R. J Diabetes Sci Tech. Interferences and Limitations in Blood Glucose Self-Testing.Published online 2016 Apr 4. doi: e10.1177/1932296816641433. URL
  3. 6 things that can affect blood glucose readings. URL. February 26, 2021. Accessed on July 23, 2023.
  4. Icodextrin in Peritoneal Dialysis Solution May Cause Falsely High Blood Glucose Readings. Pa Patient Saf Advis 2008 Jun;5(2):64-5. URL
  5. The A1c test & diabetes. NIDDK 2018. URL
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