What Is Excessive Blood Clotting?

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. For example, if a blood vessel narrows, blood flow may slow down as it moves through the vessel.

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.

Overview

Excessive blood clotting can be acquired or genetic. Acquired causes of excessive blood clotting are more common than genetic causes.

"Acquired" means that another disease, condition, or factor triggers the condition. For example, atherosclerosis (ath-er-o-skler-O-sis) can damage the blood vessels, which can cause blood clots to form. Other examples of acquired causes include smoking, overweight and obesity, and hospitalization.

"Genetic" means the condition is due to an abnormal gene. Most genetic defects that cause excessive blood clotting occur in the proteins needed for blood clotting. Defects also can occur with the substances that delay or dissolve blood clots.

Although the acquired and genetic causes of the condition aren't related, a person can have both. People who are at highest risk for excessive blood clotting have both causes.

Outlook

The outlook and treatment for excessive blood clotting depend on the cause of the blood clots, how severe they are, and how well they can be controlled.

Life-threatening blood clots are treated as emergencies. Medicines that thin the blood are used as routine treatment for blood clotting problems. Some people must take these medicines for the rest of their lives.

With medicines and ongoing care, most people who have excessive blood clotting can successfully manage it.

September 2008