Blood Clots Fact Sheet

Find out what you need to know about blood clots.

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How to Prevent Blood Clots (2:30)

Anyone who’s made a long-haul flight has heard of deep-vein thrombosis or DVT, as it’s commonly known. Longer periods of sitting, driving and flying have put more people at risk for clots. Should you be worried? Find out where exactly these clots come from, who’s at risk and how you can prevent them from forming.

What Is a Blood Clot?

Blood is supposed to clot when blood vessels are damaged. In doing so, they prevent blood from leaking out in places where it shouldn’t be while the body repairs the vessel wall. In healthy individuals, clotting generally provides a beneficial service and keeps the clot out the way of blood flowing past inside the vessel. Unfortunately, certain conditions that damage blood vessels and increase inflammation in the body can trigger the clotting system unnecessarily, leading to formation of a clot that blocks blood flow.

There are two main types of concerning clots: DVT and pulmonary embolus (PE). The DVT is often a precursor to the PE. Here’s how it works. As blood gets stuck behind a blockage (like a folded knee), certain components of the blood build up. If they congregate in an area more prone to damage or inflammation, a clot might start to form, setting off a chain reaction that grows and grows, blocking the vessel. This type of clot is called a deep-vein thrombosis (DVT). If a piece of that clot happens to break free, it can travel through your blood stream and lodge in your lungs. This blocks blood flow and prevents your body from getting oxygen, which can be deadly. This is called a pulmonary embolism (PE).

Who’s at Risk?

The following conditions can put you at risk for clotting:

  • Vein injury caused by fractures, muscle injury or surgery.
  • Slowed blood flow with long periods of sitting (especially cross-legged), being confined to bed, being paralyzed or limited movement.
  • Increased estrogen caused by birth control pills or hormone replacement therapy.
  • Chronic illnesses including heart diseasediabetes, lung disease, cancer and inflammatory conditions like Crohn’s disease, ulcerative colitis, lupus or rheumatoid arthritis.
  • Age, with risk increasing over time.

What are the Symptoms?

The symptoms vary depending on the type of clot. For a DVT, you might experience pain, swelling, redness and tenderness in the area. If a PE has occurred, you’ll have trouble breathing, chest pain, a fast or irregular heart rate and low blood pressure that may cause you to faint.

What Can I Do to Prevent Them?

Interrupted blood flow is a major contributor to blood clot formation. To keep this from happening, move every couple of hours in situations where you aren’t moving around a lot. Clots occur on planes, especially flights shorter than eight hours. If you’re on a long flight, get up and walk around every two to three hours. Exercise your legs while sitting, and avoid tight clothing.

If you’ve had recent surgery or have been confined to be bed because of illness, get moving as soon as possible. While you might not feel that well, short bouts of movement will help prevent potentially deadly blood clots and your medical team should encourage you in doing so.

Losing weight and staying active is also a great way to avoid clots. Diseases like diabetes and high cholesterol that are associated with inactivity increase inflammation and damage the walls of your blood vessels. Keeping your body generally healthy will have the side effect of decreasing you clot risk.

When Should I Worry?

If you have a chronic condition that puts you at risk for clots, you’ve probably already talked to you doctor about it. If you think you might be at risk, ask your doctor about your condition and whether you should be taking precautions. Remember, it’s all about context. Most healthy individuals who are disease-free and live active, healthy lifestyles are at very low risk for blood clots even when they’re immobile for long periods of time. If you ever experience symptoms of what you think might be a DVT, see a doctor immediately. If you have symptoms of a PE, especially sudden chest pain and trouble breathing, you should go to the emergency room.