A blood clot is a coagulation of the blood in your body. On the positive side, coagulation forms to help to stop excessive bleeding when you are injured. After which the clot will usually dissolve naturally after the injury has healed. It is when a blood clot forms independently from an injury or open wound and is not absorbed by the body, where it can be quite dangerous.
Clots can form due to substances in the skin or blood vessel walls, high levels of cholesterol, or of the pallets in the blood tend to stick together and form blockages. The body will not break these clots down because of various reasons, from some drugs such as aspirin and other blood thinners, or conditions such as hemophilia. The body does not have the right kinds of proteins to stop clotting in the blood.
If a blood clot forms in an artery or vein it can restrict blood flow to the heart and other organs, therefore, becoming life threatening. Symptoms include a chest pain or heaviness if the clot is near the heart. A weakness in the face, arms or legs, headache and dizziness for clots affecting the brain. In the lung, you may fee a sharp pain, shortness of breath, fever, and sweating, and in the abdomen, severe pain, vomiting, and diarrhea.