Erythrocyte specific volume, also called erythrocyte pressure volume, is the volume of all red blood cells in the peripheral blood as a percentage of the total blood volume. It is 40%-50% for normal adult males and 37%-48% for adult females. A high erythrocyte specific volume can be seen in two conditions, the first condition, an increase in the number of red blood cells. In the second condition, a decrease in blood volume. Increased erythrocyte count can be seen in myeloproliferative disorders such as true erythropoietic disorders, primary thrombocytosis, early stages of myelofibrosis, etc. Also certain long-term hypoxic diseases can cause an increase in the number of red blood cells, such as chronic obstructive pulmonary disease, congenital cyanotic heart disease, etc. Decreased blood volume can be seen after massive dehydration of the body, such as violent vomiting and diarrhea. As a result of the decrease in blood volume, it eventually causes an increase in the erythrocyte specific volume.