Key Points

• Excessive blood clotting is a condition in which blood clots form too easily or don't dissolve properly.
• Normally, blood clots form to seal small cuts or breaks on blood vessel walls and stop bleeding. Blood clots also can form due to slow blood flow in the blood vessels.
• There are many causes of excessive blood clotting. The condition may be due to problems with the blood, blood vessel defects, or other factors. Regardless of the cause, problem blood clots can limit or block blood flow. This can damage the body's organs or even cause death.
• Excessive blood clotting can be acquired or genetic. "Acquired” means that another disease, condition, or factor triggers the condition. "Genetic" means the condition is due to an abnormal gene.
• People at highest risk for excessive blood clotting have both genetic and acquired risk factors.
• Signs and symptoms of excessive blood clotting depend on where the clots form. Signs and symptoms may include chest pain; shortness of breath; upper body discomfort; pain, redness, warmth, and swelling in the lower leg; ongoing headaches; speech changes; paralysis (an inability to move); dizziness; and trouble speaking and understanding.
• If your doctor thinks that you have excessive blood clotting based on your signs and symptoms, he or she will look for the cause of the condition. Your doctor will ask about your medical and family histories and review the results from a physical exam and tests.
• Excessive blood clotting is treated with medicines. Depending on the size and location of the clot(s), you may need emergency treated and/or routine treatment. Long-term control of problem blood clotting is treated with blood-thinning medicines over time. Some people must take blood thinners for the rest of their lives.
• You can't prevent genetic causes of excessive blood clotting. However, you can take steps to control or avoid some acquired risk factors. (For more information, see "How Can Excessive Blood Clotting Be Prevented?")
• If you have excessive blood clotting, you should know the signs and symptoms of problem blood clots, take all of your medicines as prescribed, and get ongoing medical care.
• The outcome for people who have excessive blood clotting depends on the underlying cause of the condition. With medicines and ongoing care, most people who have the condition can successfully manage it.