Polycythemia vera is a rare type of blood cancer leading to an increase in all blood cells, but particularly in red blood cells. Patients are hence typically hypervolemic and with elevated hemoglobin concentration. The extra blood cells and platelets cause the blood to be thicker than normal and slow down the flow of blood, reducing oxygen supply to parts of the body. As a result, abnormal blood clots are more likely to form and block the flow of blood through arteries and veins. Individuals with polycythemia vera have an increased risk of deep vein thrombosis, pulmonary embolism, risk of heart attack and stroke caused by blood clots in the heart and brain. Thicker blood also doesn’t flow as quickly to your body as normal blood. Despite the augmented oxygen transport capacity associated to a higher red blood cell volume the thicker blood causes a slowed blood flow and limits organs from getting enough oxygen and polycythemia vera patients often experience fatigue, weakness and shortage of breath.