Why does chemotherapy cause easy bleeding and bruising?

Some cancer treatments, such as chemotherapy and targeted therapy, can raise your risk of bleeding and bruising. They can lower the number of platelets in the blood. Platelets are the cells that help your blood clot and stop bleeding.

When your platelet count is low, you may bruise or bleed a lot or very easily. You may also see tiny purple or red spots on your skin. A low platelet count is called thrombocytopenia. It's important to tell your doctor or nurse if you notice any of these changes.

Some bleeding problems need a call right away. Those include bleeding that doesn't stop after a few minutes, bleeding from your mouth or nose, red or pink urine, and black or bloody stools. So do head and vision changes, such as bad headaches, confusion, or feeling very sleepy. Your health care team can explain steps to lower your risk. They can also tell you which signs mean you should call them or go to the emergency room.