In patients with a normal hematocrit, the fasting whole blood glucose is 12-15% less than the plasma glucose. This is due to differences in the water content between the water phase of red blood cells and plasma.


Most clinical laboratory analyzers test serum or plasma. Most glucose self-monitoring meters test whole blood.


whole blood glucose in mg/dL =

= 0.875 * (plasma glucose in mg/dL)


plasma glucose in mg/dL =

= 1.142 * (whole blood glucose in mg/dL)


For patients with anemia, the following equation may be used:


whole blood glucose in mg/dL =

= ((1 - (0.0024 * (hematocrit in percent))) * (plasma glucose in mg/dL))


plasma glucose in mg/dL =

= (whole blood glucose in mg/dL) / (1 - (0.0024 * (hematocrit in percent)))



• The hematocrit is in percent (between 0 and 100), not a decimal fraction.


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