Blood Clots

Source: MedlinePlus Health Topics, U.S. National Library of Medicine

Last synced 8/9/2026Status: primary verified

What is a blood clot? A blood clot is a mass of blood that forms when platelets , proteins, and cells in the blood stick together. When you get hurt, your body forms a blood clot to stop the bleeding . After the bleeding stops and healing takes place, your body usually breaks down and removes the blood clot. But sometimes the blood clots form where they shouldn't, your body makes too many blood clots or abnormal blood clots, or the blood clots don't break down like they should. These blood clots can be dangerous and may cause other health problems. Blood clots can form in, or travel to, the blood vessels in the limbs, lungs, brain, heart, and kidneys. The types of problems blood clots can cause will depend on where they are: Deep vein thrombosis (DVT) is a blood clot in a deep vein, usually in the lower leg, thigh, or pelvis. It can block a vein and cause damage to your leg. A pulmonary embolism (PE) can happen when a DVT breaks off and travels through the bloodstream to the lungs. A PE, especially if it is large, can damage your lungs and prevent your other organs from getting enough oxygen. Cerebral venous sinus thrombosis (CVST) is a rare blood clot in the venous sinuses in your brain. Normally the venous sinuses drain blood from your brain. CVST blocks the blood from draining and can cause a hemorrhagic stroke . Blood clots in other parts of the body can cause problems such as an ischemic stroke , a heart attack , kidney problems , kidney failure , and pregnancy-related problems . Who is more likely to develop blood clots? Certain factors can raise your risk of developing blood clots: Atherosclerosis Atrial fibrillation Being overweight or having obesity Cancer and cancer treatments Certain genetic disorders Certain surgeries COVID-19 Diabetes Family history of blood clots Overweight and obesity Pregnancy and giving birth Serious injuries Some medicines, including birth control pills Smoking Staying in one position for a long time, such as being in the hospital

Educational only

This information is for general education and is not medical advice. Always talk to a licensed U.S. clinician about your situation, medications, or treatment decisions.