Yes, leukemia can cause blood clots, and the risk is significant. People with blood cancers like leukemia are up to 28 times more likely to develop a clot than the general population. This happens through several overlapping mechanisms: the leukemia itself disrupts normal clotting processes, treatments can tip the balance further, and even the medical devices used during care add risk.
How Leukemia Triggers Clotting
Leukemia increases clot risk through at least three distinct pathways, all driven by the abnormal white blood cells (called blasts) flooding the bloodstream.
First, leukemic blasts are stiffer and larger than normal white blood cells. They physically clog small blood vessels, reducing blood flow and starving downstream tissue of oxygen. This alone can trigger clotting at the site of obstruction.
Second, leukemic cells release inflammatory signals that activate the lining of blood vessels. These signals cause the vessel walls to become “sticky,” expressing surface proteins that grab onto passing leukemic cells and pile them up. This creates a snowball effect where more cells adhere, more inflammation follows, and the vessel narrows further.
Third, leukemic blasts release enzymes that directly damage blood vessel walls. This damage exposes tissue beneath the vessel lining to the bloodstream, which is one of the body’s strongest triggers for forming a clot. The same damage can also cause small bleeds in surrounding tissue, creating the paradox where leukemia patients face both clotting and bleeding risks simultaneously.
Risk Varies by Leukemia Type
Not all leukemias carry the same clot risk. In a large study of over 5,300 people with acute myeloid leukemia (AML), about 5.2% developed a blood clot within two years. Roughly 3.6% had deep vein thrombosis or a pulmonary embolism (a clot that travels to the lungs), while another 1.6% developed clots in the upper body veins.
Acute promyelocytic leukemia (APL), a subtype of AML, carries a uniquely dangerous clotting complication called disseminated intravascular coagulation, or DIC. In DIC, the clotting system activates throughout the entire body at once, using up clotting proteins so rapidly that dangerous bleeding and clotting happen at the same time. One study of 116 APL patients found that nearly 78% developed this condition. A larger U.S. hospital analysis found DIC in about 19% of APL admissions. The leukemic cells in APL are especially potent triggers because they carry high levels of a protein called tissue factor on their surface, which directly activates the clotting cascade.
In acute lymphoblastic leukemia (ALL), the clot risk is heavily influenced by treatment. One study of 455 patients with acute leukemia found clots in 12.1% overall, with roughly equal rates in AML and ALL.
Treatment Can Increase the Risk
Several standard leukemia treatments independently raise clot risk, sometimes substantially.
One chemotherapy drug commonly used in ALL works by starving leukemia cells of an amino acid they need to survive. A side effect is that the liver also reduces its production of natural blood-thinning proteins. In studies, this drug cut levels of one key anticoagulant protein nearly in half after just four infusions, dropping from a healthy 120% to 59%. The result is blood that clots more easily than it should.
Steroids, which are a cornerstone of many leukemia treatment plans, compound this problem. They boost production of multiple clotting factors while simultaneously suppressing the body’s ability to dissolve clots. When steroids and the amino acid-depleting drug are given together, clot rates in one study reached 11.6%, compared to 2.5% when the drug was used in a protocol with less steroid overlap. That combination carried nearly eight times the odds of developing a clot.
Central Lines Are a Major Contributor
Most leukemia patients receive chemotherapy through a central venous catheter, a tube inserted into a large vein in the chest or arm. These devices are essential for treatment but create a physical surface where clots readily form. In the study of 455 acute leukemia patients, half of all blood clots were directly associated with a central line. Catheter-related clot rates in leukemia patients have been reported between 6% and 15% across multiple studies.
Having a central line raised the risk of deep vein thrombosis or pulmonary embolism by 60% in one large analysis of AML patients. This is a practical concern because these catheters often stay in place for weeks or months during intensive treatment cycles.
Low Platelet Counts Don’t Protect Against Clots
One of the most counterintuitive aspects of clotting in leukemia is that it happens even when platelet counts are very low. Platelets are the blood cells responsible for forming clots, so you might expect that having too few would make clotting impossible. It doesn’t.
Many leukemia patients develop severely low platelet counts, either from the disease crowding out normal blood cell production or from chemotherapy. Yet these patients still form dangerous clots. The prothrombotic state created by leukemic cells, inflammatory signals, vessel damage, and treatment effects overrides the low platelet count. This creates a difficult treatment situation: giving blood thinners to treat the clot raises the risk of serious bleeding in someone whose platelets are already dangerously low. Prolonged low platelet counts lasting more than 30 days have been linked to higher risks of both bleeding and recurrent clotting.
Other Risk Factors That Stack Up
Beyond the disease and its treatment, several patient-specific factors increase clot risk further. In the large AML study, women had a 40% higher risk of developing a clot than men. Patients with more pre-existing health conditions (measured by a comorbidity index) had up to 80% higher risk. Obesity, prolonged immobility during hospitalization, and abnormalities in blood counts all contribute as well. These factors don’t act in isolation. They layer on top of the leukemia-specific risks, meaning a woman with AML, a central line, and limited mobility during induction chemotherapy faces a substantially compounded risk.
Warning Signs to Recognize
Blood clots in leukemia patients most commonly show up as deep vein thrombosis in the arms or legs, or as clots around central lines in the chest and upper body. The signs to watch for include swelling, redness, or pain in one arm or leg, particularly if it comes on suddenly or affects just one side. If your treatment involves a port or catheter, new swelling or redness around that site can signal a clot forming there.
A clot that breaks free and travels to the lungs (pulmonary embolism) is a medical emergency. Sudden shortness of breath, chest pain, rapid heartbeat, or lightheadedness during leukemia treatment warrants immediate emergency care. Abdominal clots, though less common, can cause sudden belly pain.
Because leukemia patients are often already dealing with fatigue, bruising, and general discomfort from treatment, new or asymmetric swelling and unexplained pain are the most reliable distinguishing signals that a clot may be forming rather than a general treatment side effect.