People with cancer, especially those receiving treatment, are at risk for blood clots. A person with a clotting disorder may get blood clots in the veins or arteries if the blood forms a clot too fast.
Normal blood clotting, called coagulation, is a complex process in which platelets (specialized blood cells) and different proteins in the blood (called clotting or coagulation factors) clump together to heal broken blood vessels and control bleeding. Coagulopathies (disorders of the blood clotting system) occur when clotting factors are missing or damaged, when there is a low number of platelets, or when the platelets don't work correctly.
Blood clots are a serious side effect of cancer and cancer treatment. Read ASCO's recommendations for preventing and treating blood clots  for information on the causes, treatments, and questions to ask your doctor about blood clots.