How Blood Clots Form

The body has a natural clotting system that normally helps stop bleeding when you get a cut or injury. Sometimes this system can become overactive or disrupted. When this happens, blood clots can form in places where they are not needed, such as the veins in your legs or arms (deep vein thrombosis) or the lungs (pulmonary embolism).

How deep vein thrombosis (DVT) develops – Watch the following video from Thrombosis Canada to learn how blood clots form in the deep veins of the legs or arms.

How Pulmonary Embolisms (PE) Develop – Watch the following video from Thrombosis Canada Understand how a clot can travel to the lungs and affect blood flow. 

• Immobility: Sitting or lying still for long periods slows blood flow. This can happen during a hospital stay, after surgery, on long trips (driving or flying), or when sitting/standing at work for a long time.
• Surgery or Injury: Surgery, medical procedures, or injuries (such as broken bones or severe bruising) can damage blood vessels, triggering clot formation
• Health conditions: Illnesses such as cancer, inherited blood disorders, and some hormone therapy (pregnancy/menopause) can affect how blood clots and increase the risk of developing a blood clot
• Lifestyle factors: Smoking and low physical activity can reduce circulation, damage blood vessels, and increase the risk of clot formation
• Age over 60: As we age, veins and valves can weaken, and age-related health conditions can increase the likelihood of clot formation

Early recognition of symptoms and prompt medical attention are critical to reduce risk of serious complications.

Learn more about risk factors