Spurious elevation of the electronically determined mean corpuscular volume and hematocrit caused by hyperglycemia.

Following normalization of blood glucose levels, a marked change in the MCV and in the calculated hematocrit was observed in five patients with transient severe hyperglycemia. The addition of varied concentrations of glucose to blood samples from healthy volunteers and from patients with microcytic, macrocytic, and normocytic anemia produced a similar and proportionate increase in the MCV. Increases in urea concentration to clinically relevant levels had no effect.