Ask The Expert
Monitoring

When blood is collected, whether at the lab, or using home blood glucose monitoring, it is whole blood. However, when the laboratory measures glucose, it first spins the tube of blood in a centrifuge; this causes the red blood cells to separate and fall to the bottom of the tube; the liquid part of the blood—called plasma—is actually a clear pale yellow color. The laboratory measures glucose from this plasma part of the blood. Because the red blood cells are absent from this part of the blood, there is more room for glucose to occupy this space.

What this means is that Plasma Glucose is generally about 11% higher than Whole Blood Glucose.

In the past, the original home blood glucose meters were all whole blood calibrated—but since laboratory standards are based on plasma values, diabetes specialists and diabetes educators requested that home blood glucose meters should be plasma calibrated so that they would correlate with the laboratory glucose value. Because of this, for several years now, almost all meters on the market are plasma calibrated.

FreeStyle meters and Precision meters are calibrated on plasma equivalent values.