Erythrocyte pressure volume, also known as erythrocyte specific volume, refers to the ratio of the volume of red blood cells in the blood. Its normal range is 0.4-0.5 for adult males and 0.37-0.48 for adult females. erythrocyte pressure volume is affected by the increase or decrease in the number of red blood cells, changes in plasma volume, and the size of red blood cell volume. Increased erythropoietic pressure volume is commonly seen in hematoconcentration caused by various reasons, such as profuse sweating, severe diarrhea, vomiting, etc. It is also seen in absolute increase of red blood cells caused by true erythropoietic disease, primary thrombocytosis, etc. Decreased erythrocyte pressure volume is commonly seen in various cases of anemia. In anemia, the number of red blood cells decreases, resulting in a decrease in red blood cell pressure, commonly seen in iron deficiency anemia, aplastic anemia, megaloblastic anemia, etc.