Erythrocytopenia is a measurement of the diameter, size, thickness of the erythrocyte. The diameter of erythrocytes (E) measured on fixed and stained thin smears of blood through the eyepiece micrometer - line inserted into eyepiece or in a special nozzle. Define D 200 erythrocytes. In normal blood magnitude D. ranging from 4.75 V to 9.5 MK, average diameter 7,2 - 7,5 MK. The volume of erythrocyte determined by the hematocrit (see). Knowing the amount of erythrocytes in percent, calculate their volume in 1 mm^{3} and divide this amount by the number of cells in 1 mm^{3}. The volume of erythrocyte normal 88-90 MK^{3}. The thickness of the erythrocyte (T) is determined by dividing its total volume by the area
S[S=3,14x (D/2)^{2}]. Normal T=1,9-2,1 MK. The shape of the red blood cells determines the ratio D/T (in the norm of 3.3), when it is increased erythrocyte flattened (planolit), with a decrease in its approaches spherical (Ferozit).

Erythrocytopenia is the determination of the amount of erythrocytes (diameter, length and thickness).

The diameter of erythrocytes set in three ways: direct microscopic, by way of indirect determination and electronic.

In practice apply microscopic method with ocularstream. Painted the drug is placed under the microscope and a ruler of ocularocular measure the diameter of 200 different red blood cells, remove the average diameter, maximum, and minimum. In norm the diameter of erythrocytes ranging from 4.75 V to 9.5 MK. Building curve Price-Jones: the amount of erythrocytes lay on the x-axis and the number of erythrocytes on the axis of ordinates. Peak (peak) this curve represents the average diameter (in norm 7,2-7,5 MK).

Indirect way diameter of erythrocytes measure the diameter of the colored rings in the office of Pipera.

Electronic measurement of red blood cells is carried out in the electronic counter "Teleskop" (description when the device).

The ratio between the volume of plasma and cell volume determined in hematocrit (normal average 44).

The average volume of erythrocytes calculate the hematocrit and the number of red blood cells in 1 mm^{3}. In healthy people, the average volume of erythrocytes is 88-90 MK^{3}.

The thickness of the erythrocyte determined according to the volume and diameter. Cm. also the Blood (research methods).