Red blood cells

Blood Clots


Healthgrades Editorial Staff

What are blood clots?

A blood clot is an organized clump of hardened blood. Normal blood clotting helps stop blood loss, such as when you get a minor cut or scrape. However, a blood clot that forms inside a blood vessel (artery or vein) or in the heart is called a thrombus and is a serious medical condition. Blood clots can form in the superficial veins just below your skin, or they can form in the deeper, large veins (deep vein thrombosis). Blood clots can also dislodge and move from their initial location to another. This is called an embolism.

Blood clots are more common in people who cannot move around easily because of advanced age, injury, surgery, or disease. People with certain blood clotting disorders that make their blood clot more easily have an increased risk of developing blood clots in the deep veins. In addition, certain cancers and estrogen-based medications can increase your risk for blood clots.

A blood clot is dangerous because it can block or reduce the flow of blood to the part of the body in which it formed. This blockage causes a lack of oxygen to the tissues (called ischemia) and eventually leads to permanent tissue damage.

Blood clots can also break apart from the blood vessel wall and travel to another location, such as the brain or lung, leading to catastrophic consequences. A blood clot that travels to the lung can lead to a pulmonary embolism, permanent lung damage, and even sudden death. A blood clot that travels to the brain can cause a stroke. A blood clot that forms within the arteries of the heart can cause a heart attack.

Your risk of developing blood clots can be minimized by making certain lifestyle changes and following your doctor’s treatment plan. In particular, regular exercise, smoking cessation, elevating your feet, and frequently changing your body position can help prevent blood clots from forming.

Medical Reviewers: William C. Lloyd III, MD, FACS Last Review Date: Nov 3, 2016

© 2018 Healthgrades Operating Company, Inc. All rights reserved. May not be reproduced or reprinted without permission from Healthgrades Operating Company, Inc. Use of this information is governed by the Healthgrades User Agreement.

View Sources

Medical References

  1. About Heart Attacks. American Heart Association.
  2. What is pulmonary embolism? National Heart, Lung and Blood Institute, National Institutes of Health.
  3. Collins RD. Differential Diagnosis in Primary Care, 5th ed. Philadelphia: Lippincott, Williams & Williams, 2012.
  4. Domino FJ (Ed.) Five Minute Clinical Consult. Philadelphia: Lippincott Williams & Wilkins, 2013.

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