Due to factors such as genetics, smoking, and living at high altitudes, polycythemia causes an increased number of red blood cells which leads to elevated levels of hemoglobin, hematocrit, and red blood cell count. Symptoms include headache, dizziness, and skin itching. Diagnosis involves blood tests and bone marrow tests. Treatment includes phlebotomy to reduce blood volume, medications to decrease blood cell production, and lifestyle changes like exercise and avoiding tobacco. Nursing care focuses on monitoring for blood clots, administering treatments, providing education, and addressing pain and nutrition needs.