If blood moves too slowly through your veins, it can cause a clump of blood cells called a clot. When a blood clot forms in a vein deep inside your body, it causes what doctors call deep vein thrombosis (DVT). This is most likely to happen in your lower leg, thigh, or pelvis. But it can occur in other parts of your body, too.
DVT can lead to major health problems. In some cases, it can be fatal. That’s why if you think you have one, you must see a doctor right away.