Phlebotomy is the removal of blood from a vein. It is the usual starting point of treatment for most patients. A volume of blood is drawn at regular intervals and the hematocrit concentration is brought down to normal values within a period of weeks to months. The procedure is identical to that used for donating blood to a blood bank. The immediate effect of phlebotomy is to reduce the hematocrit concentration, which usually results in the improvement of certain symptoms such as headaches, ringing in the ears and dizziness. Eventually, phlebotomy results in iron deficiency.
Phlebotomy may be the only form of treatment required for many patients, sometimes for many years. Acceptable disease control may be achieved with withdrawal of a volume of blood every few months. Patients may feel tired afterward and need to rest for a short time.