1. Glucose Levels Differ Depending on Where You Measure
Our body’s blood glucose levels show slight differences depending on the type of blood measured. The self-monitoring glucose meters we use at home use ‘capillary blood’ from the fingertip, while the blood drawn at a hospital for diagnosis is ‘venous blood’ from the arm.
2. Why Do the Levels Differ?
– Fasting State: When you have fasted, all body tissues use a similar amount of glucose, so there is almost no difference between fingertip and venous blood glucose levels.
– Post-Meal State: After a meal, glucose spreads throughout the body via the arteries. It enters the cells of peripheral tissues, like the fingertips, before returning to the veins. Therefore, after a meal, the capillary blood glucose at the fingertip is usually slightly higher than the venous blood glucose from the arm.
3. The Diagnostic Standard: ‘Venous Plasma Glucose’
Because of these differences, the official diagnostic criteria for diabetes used worldwide (e.g., fasting glucose of 126 mg/dL) are based on the glucose concentration in ‘venous plasma,’ which is what’s left after blood cells are separated from a venous blood sample drawn at a hospital. Self-monitoring meters that use fingertip blood are intended for ‘monitoring’ daily fluctuations, not for diagnosis. Although modern meters have advanced calibration to provide results similar to venous plasma, they are not used for an official diagnosis.
Summary: Blood glucose levels can vary depending on the type of blood measured. The official diagnostic standard for diabetes is venous blood drawn at a hospital, not capillary blood from a fingertip.
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