Relative polycythemia, also called hemoconcentration, is caused by a decrease in plasma volume rather than an increase in red blood cells. It can result from losses of body fluids due to diarrhea, vomiting, diuretic use, or adrenal insufficiency. Absolute polycythemia is caused by an increased production of red blood cells and can be primary, such as polycythemia vera, or secondary to tissue hypoxia due to conditions like heart or lung disease. Polycythemia vera is a chronic myeloproliferative disorder characterized by increased red blood cell volume and hyperviscosity syndrome. Treatment focuses on phlebotomy, medications to suppress bone marrow, and managing symptoms like