Therapeutic phlebotomy, the controlled removal of blood to treat disease, is used for a handful of conditions where the body accumulates too much iron or produces too many red blood cells. The most common are hereditary hemochromatosis and polycythemia vera, but several other conditions also call for it. Here’s a closer look at each one and why blood removal helps.
Hereditary Hemochromatosis
Hemochromatosis is the single most common reason for therapeutic phlebotomy. In this genetic condition, the body absorbs far more iron from food than it needs, and because humans have no efficient way to excrete excess iron, it builds up in the liver, heart, pancreas, and joints over years. Left untreated, the iron deposits can cause cirrhosis, diabetes, heart failure, and joint pain.
Phlebotomy works because each unit of blood removed contains iron locked inside red blood cells. To replace those cells, the body pulls iron out of its storage sites, gradually depleting the surplus. Treatment typically has two phases. During the initial “depletion” phase, you may need blood drawn every one to two weeks until your ferritin (a blood marker of stored iron) drops below 50 micrograms per liter. After that, a maintenance phase keeps ferritin below 100 micrograms per liter, usually requiring phlebotomy only a few times a year. Most people with hemochromatosis continue maintenance phlebotomy for life, but the sessions become infrequent enough that they barely disrupt a normal routine.
Polycythemia Vera
Polycythemia vera is a slow-growing blood cancer in which the bone marrow overproduces red blood cells. The extra cells thicken the blood, raising the risk of blood clots, stroke, and heart attack. Symptoms often include headaches, dizziness, itching (especially after a warm shower), and a flushed or reddish complexion.
The treatment goal is to keep hematocrit, the percentage of blood volume occupied by red cells, below 45%. A landmark trial published in the New England Journal of Medicine showed that patients maintained below this threshold had significantly fewer cardiovascular events than those kept at a higher level. During the initial phase, phlebotomy sessions may happen every few days. A common protocol removes about 350 milliliters per session, roughly the same as a standard blood donation, repeated until hematocrit reaches the target. Once under control, most people shift to maintenance sessions every one to three months, depending on how quickly their counts climb back up.
Porphyria Cutanea Tarda
Porphyria cutanea tarda (PCT) is a rare disorder in which the body can’t properly make heme, the iron-containing molecule in red blood cells. The result is a buildup of light-sensitive chemicals called porphyrins, which cause painful blistering on sun-exposed skin, particularly the hands, forearms, and face. The skin can also become fragile, scarring easily from minor bumps.
Excess iron is a central driver of PCT because it interferes with a key enzyme in heme production. Removing iron through phlebotomy restores that enzyme’s function and lowers porphyrin levels. Sessions are typically spaced further apart than in hemochromatosis, often every two weeks, and continue until iron stores normalize. Most people see their skin symptoms improve within several months. In cases where anemia prevents phlebotomy, low-dose antimalarial medication can be used instead.
Secondary Erythrocytosis
Secondary erythrocytosis is an overproduction of red blood cells driven not by a bone marrow disorder but by an outside trigger. The most common causes are chronic lung disease (like COPD), obstructive sleep apnea, long-term smoking, and living at high altitude. In each case, the body senses lower oxygen levels and responds by churning out more red cells to compensate.
Phlebotomy isn’t automatically needed here. Treating the underlying cause, using supplemental oxygen for lung disease or a CPAP machine for sleep apnea, is always the first step. But when hematocrit climbs above 60% to 65%, the blood becomes dangerously thick regardless of the cause, and phlebotomy is recommended. At those levels, people often experience impaired alertness, dizziness, headaches, and reduced exercise tolerance, along with a sharply increased risk of stroke, heart attack, and deep vein thrombosis.
Non-Alcoholic Fatty Liver Disease
A subset of people with non-alcoholic fatty liver disease (NAFLD) have elevated iron levels in the liver, a pattern sometimes called “dysmetabolic iron overload.” This extra iron worsens inflammation and can accelerate the progression from simple fatty liver to more serious scarring. Phlebotomy to reduce iron stores has been used in these patients, though it is not a standard first-line treatment for everyone with NAFLD. It tends to be reserved for those whose blood tests confirm meaningful iron excess alongside their liver disease.
Post-Transplant Erythrocytosis
After a kidney transplant, some recipients develop an abnormally high red blood cell count, a condition called post-transplant erythrocytosis. It occurs in roughly 10% to 15% of kidney transplant patients, usually within the first two years. The new kidney sometimes overproduces erythropoietin, the hormone that signals the bone marrow to make red cells, leading to thickened blood and a higher clot risk. When medications don’t bring the count under control, therapeutic phlebotomy is used to keep hematocrit at a safe level.
Iron Overload From Chronic Transfusions
People who receive regular blood transfusions for conditions like sickle cell disease, thalassemia, or myelodysplastic syndromes gradually accumulate iron because each unit of transfused blood delivers a significant iron load and the body has no way to shed it. Over months and years, this iron deposits in the liver and heart.
In sickle cell disease specifically, partial manual exchange phlebotomy, removing blood before a transfusion, can reduce net iron accumulation by 15% to 20% compared to simple transfusion alone. Full exchange transfusion cuts the iron load by about 85%. For patients who eventually stop needing regular transfusions but still carry excess stored iron, straightforward phlebotomy sessions can bring levels back down. However, many chronically transfused patients remain anemic, making standard phlebotomy unsafe. In those cases, iron chelation therapy (medications that bind iron so the body can excrete it) is used instead.
What to Expect During a Session
A typical session looks almost identical to donating blood. You sit in a reclining chair, a needle is placed in a vein in your arm, and 350 to 500 milliliters of blood is collected into a bag. The whole process takes about 15 to 30 minutes. Afterward, you’re encouraged to drink extra fluids and avoid strenuous activity for the rest of the day. Lightheadedness and mild fatigue are the most common side effects, and they usually resolve within a few hours.
People with severe anemia or cardiovascular instability are generally not candidates for phlebotomy, since removing blood could worsen their condition. In those situations, alternative treatments like chelation therapy or medication adjustments are used to manage the underlying problem.