Testing blood glucose is a cornerstone of Diabetes management. The precision of monitoring often defines success, as it guides decisions on diet, physical activity, and medication, including insulin. While home glucose meters have made testing accessible, accuracy is paramount.
Glucometer testing must be done with meticulous care. Any low or high readings that seem out of place must be interpreted cautiously, often in consultation with a healthcare provider. Here are real-life examples where the numbers lied.
Story 1: The Sweet Skin Error
I saw a 35-year-old man who recorded persistently high capillary glucose levels, yet his laboratory results were normal. On careful review, he admitted to testing immediately after peeling fruits without washing his hands. Trace amounts of sugar on his fingertips contaminated the strips, causing spuriously high readings.
The Lesson: Always wash and dry your hands before testing. Invisible residues from food, lotions, or even alcohol sanitizers can alter blood glucose levels, sometimes by 20-40 mg/dL.
Story 2: The Late Test
A 50-year-old gentleman noticed unexplained, erratic glucose fluctuations. I found he was using expired strips and, moreover, storing them in a humid environment. Degraded enzymes from the expired strips and moisture from humidity both resulted in falsely low readings.
The Lesson: Store glucose strips in their tightly closed, original container, away from heat and humidity. Never use expired strips.
Story 3: The Lag Test
A young sportsman complained that his continuous glucose monitoring (CGM) readings spiked after meals, while his finger-stick glucometer readings were normal. He did not account for the fact that CGM reports can lag behind actual blood glucose by up to 15 minutes (called the lag effect). This is because the CGM sensor sits in the fluid between cells, and it takes time for this fluid’s glucose to align with blood glucose levels.
The Lesson: A CGM lag is normal, especially after meals. When in doubt, or when making an immediate treatment decision, confirm the reading with a finger-stick glucometer.
Story 4: The Blood Effect
A young marathon runner with Type 1 Diabetes had a fantastically controlled HbA1c of 5.6%. However, both his home glucometer and CGM readings were consistently high. Special tests revealed he had thalassemia, a hemoglobin abnormality. This condition, along with certain anemias, can interfere with HbA1c testing, making it falsely low.
The Lesson: If your three-month average (HbA1c) is low but your daily glucose readings are high, discuss it with your doctor. In this situation, it may be better to trust the blood glucose readings, not the HbA1c.
We must also remember that dehydration, common during long marathon runs, can spuriously elevate blood glucose readings. It Glucose measurement is all-important in Diabetes because it guides every aspect of care, from nutrition and exercise to oral medications and insulin. As you read, remember that every laboratory test must be interpreted with its advantages and disadvantages in mind. When in doubt, always discuss the results with your physician.
Happy testing, happy reading.
Dr Unnikrishnan AG
Editor
