What are common causes of polycythemia?

Polycythemia is a condition characterized by an increase in the number of red blood cells in the bloodstream, leading to elevated hemoglobin levels and hematocrit values. Chronic hypoxia is a significant cause of secondary polycythemia, where the body responds to low oxygen levels by producing more red blood cells to enhance oxygen delivery to tissues. Conditions that can lead to chronic hypoxia include chronic obstructive pulmonary disease (COPD), sleep apnea, and living at high altitudes. This compensatory mechanism is the body's way of adapting to the oxygen deficit.

Dehydration can also contribute to a relative increase in red blood cells in the bloodstream. When the volume of plasma decreases due to inadequate fluid intake or excessive fluid loss, the concentration of red blood cells in the remaining plasma appears increased. This does not indicate an increase in the actual number of red blood cells but rather a decrease in plasma volume.

The combination of chronic hypoxia stimulating erythropoiesis (the production of red blood cells) and dehydration leading to hemoconcentration is why the chosen answer accurately reflects common causes of polycythemia.