Mistakes that can skew Glucometer readings - and what to do instead

For people managing diabetes or monitoring their blood sugar levels at home, a glucometer is a vital tool for daily life. But even the most reliable device can produce misleading results if not used correctly. Factors such as unwashed hands, expired strips, or improper testing techniques may affect accuracy, sometimes enough to prompt unnecessary concern or lead to missed warning signs. Understanding what influences these readings is essential to ensure that the numbers accurately reflect what is truly happening in the body.

While many patients increasingly rely on HbA1c for tracking diabetes control, it’s important to note that self-monitoring of blood glucose (SMBG) complements rather than replaces lab results. Since SMBG can sometimes show variability that HbA1c averages out, using both may provide a more complete picture of blood glucose control.

Common factors that affect accuracy
Several everyday factors can interfere with the accuracy of blood glucose readings. Being aware of these can help avoid errors and ensure that results are as reliable as possible:

• Not washing hands before testing: Even small traces of food or sugar on the fingers can give a falsely high reading. Testing without washing hands is one of the most common sources of inaccurate results.1
• Expired or improperly stored test strips: Test strips contain enzymes that degrade over time or when exposed to heat, moisture, or air.2 Using expired or improperly stored strips can compromise their effectiveness and accuracy.
• Insufficient blood sample: A drop that’s too small may not be enough for the glucometer to function correctly, leading to errors or inconsistent readings.
• Squeezing the finger excessively: Applying too much pressure to get a blood drop can mix tissue fluids with blood, affecting the test result.
• Incorrect storage conditions: Testing in very hot, cold, or humid environments can interfere with strip chemistry or device performance.3

Test strips contain reagents which interact with blood sample to provide glucose readings. And thus an improperly stored test strip container e.g. container kept open, or not closed properly, kept in direct sunlight, heat, humidity, moisture, etc. may affect the accuracy.

When to double-check or consult
Even when following all precautions, there may be times when blood sugar readings appear unexpectedly high or low.

Here’s what to consider:

• Repeat the test: Use a new strip and test again, ideally on a different finger, to rule out any sampling issues.
• Check the strip and device: Ensure the strip isn't expired and the device is clean and functioning properly.
• Consult a doctor: If readings remain inconsistent, fluctuate sharply without explanation, or don’t align with physical symptoms, it's best to consult a healthcare professional. Medical advice can help rule out device-related issues or underlying health concerns.

Over-monitoring, however, can also have downsides. Psychological stress is common among patients who constantly check their blood sugar. It is important to set realistic expectations, avoid obsessing over every number, and focus on trends rather than isolated readings. This is especially relevant with continuous glucose monitoring (CGM), which can create an overwhelming flow of data for some users.

Building a testing routine that works
For those newly diagnosed, integrating testing into daily life can feel daunting. Younger patients on intensive insulin regimens often require more frequent SMBG or CGM. From regular and structured monitoring regime e.g. pre-post meals, exercise, medications, etc., in consultation with your doctor is recommended.

What a Glucometer can (and cannot) tell you
A glucometer is a valuable tool for tracking blood sugar trends and making informed daily decisions, but it has its limitations.

What it can do:
A glucometer is a vital tool for tracking blood sugar trends. Regular and accurate use not only helps in managing diabetes but also reveals how diet and activity affect glucose levels, guiding timely treatment decisions with a doctor’s advice.

What it cannot do:
A glucometer does not diagnose diabetes, replace HbA1c tests or account for complex physiological factors that may affect blood sugar.5 It’s not a standalone tool for clinical decision-making.

Regular self-monitoring is a key part of managing diabetes effectively. Following basic hygiene, storage, and usage practices — and staying alert to anything unusual — can go a long way in ensuring that every reading is one you can trust.
References 1. https://www.fda.gov/media/80782/download 2. https://diabetesjournals.org/care/article/47/Supplement_1/S1/153952/Introduction-and-Methodology-Standards-of-Care-in 3. https://pubmed.ncbi.nlm.nih.gov/24876542/ 4. https://www.icmr.gov.in/icmrobject/custom_data/pdf/resource-guidelines/ICMR_GuidelinesType2diabetes2018_0.pdf 5. https://pmc.ncbi.nlm.nih.gov/articles/PMC2769965/

Disclaimer: The views and opinions expressed in the story are independent professional judgments of the experts, and TIL does not take any responsibility for the accuracy of their views. This should not be considered a substitute for medical advice. Please consult your treating physician for more details. This article has been produced on behalf of Roche Diabetes Care by Times Internet’s Spotlight team.