High red blood cells and hemoglobin, also known as an increase, are divided into relative and absolute increases. Relative increase is not an increase in red blood cells and hemoglobin, but a decrease in plasma and blood concentration due to dehydration, which can be seen in severe vomiting, diarrhea, profuse sweating, massive burns, uremia, diabetic ketoacidosis, etc. Absolute increase is further divided into primary increase and secondary increase. Primary hyperplasia, also called true erythrocytosis, is a hematologic neoplasm. Secondary increase is divided into physiological and pathological. Physiological increase is seen in fetuses, newborns and residents of highland areas. Pathological increase can be seen in chronic hypoxic heart and lung diseases, such as obstructive emphysema, pulmonary heart disease, cyanotic congenital heart disease; and abnormal hemoglobinopathies with low oxygen-carrying capacity; it can also be seen in certain tumors or kidney diseases, such as kidney cancer, hepatocellular carcinoma, ovarian cancer, uterine fibroids, renal embryonal tumors, as well as polycystic kidney and hydronephrosis. The secondary increase is due to an increase in erythropoietin in the blood.