Increased In:

• Anxiety or stress (related to physiological response)
• Bone marrow failure (initial response is stimulation of RBC production)
• COPD with hypoxia and secondary polycythemia (related to chronic hypoxia that stimulates production of RBCs and a corresponding increase in RBCs)
• Dehydration with hemoconcentration (related to decrease in total blood volume relative to unchanged RBC count)
• Erythremic erythrocytosis (related to unchanged total blood volume relative to increase in RBC count)
• High altitude (related to hypoxia that stimulates production of RBCs)
• Polycythemia vera (related to abnormal bone marrow response resulting in overproduction of RBCs)

Decreased In:

• Chemotherapy (related to reduced RBC survival)
• Chronic inflammatory diseases (related to anemia of chronic disease)
• Hemoglobinopathy (related to reduced RBC survival)
• Hemolytic anemia (related to reduced RBC survival)
• Hemorrhage (related to overall decrease in RBC count)
• Hodgkin’s disease (evidenced by bone marrow failure that results in decreased RBC production)
• Leukemia (evidenced by bone marrow failure that results in decreased RBC production)
• Multiple myeloma (evidenced by bone marrow failure that results in decreased RBC production)
• Nutritional deficit (related to deficiency of iron or vitamins required for RBC production and/or maturation)
• Overhydration (related to increase in blood volume relative to unchanged RBC count)
• Pregnancy (related to anemia; normal dilutional effect)
• Renal disease (related to decreased production of erythropoietin)
• Subacute endocarditis