A lung clot usually comes from another place in the body. Most often, it begins in a deep vein in the leg.[1] A clot can move along in the bloodstream. It may then lodge in an artery that supplies the lung. Doctors refer to this as a pulmonary embolism.
Learning that term can feel scary at first. Still, the process follows a fairly clear sequence: a clot forms, part of it breaks loose, and it travels to the lungs. If you understand these basic steps ahead of time, you may recognize the warning signs earlier and know when to get help. Many people have never heard the term pulmonary embolism before, so this guide explains the causes, the risk factors and the warning signs in plain language, one section at a time.
What causes blood clots in the lungs?
Most pulmonary embolisms happen when a clot forms in a deep vein—usually in the leg—and part of it travels to an artery in the lungs. This is called a pulmonary embolism (PE). Clots are more likely to develop when blood flow slows, a vein is injured, or the blood is more likely to clot. Understanding these causes can help you recognize situations that may increase your risk.
Common causes for blood clots in the lungs:
- Spending extended periods of time seated for long trips or flights
- Surgery or injury in the last few days or weeks.
- Resting for extended periods.
- Some blood clotting problems
- Walls of a blood vessel becoming damaged
What health conditions and lifestyle factors raise the risk of lung blood clots?
Some medical conditions, medicines, and situations can increase the risk of developing a blood clot that may travel to the lungs. Having more than one risk factor can raise the likelihood further. Knowing your risk factors can help you discuss prevention with your healthcare team.
Risk Factors for Blood Clots
- Having had a previous DVT or pulmonary embolism, or having an inherited blood-clotting disorder [4]
- Having excess weight or limited movement.
- Having active cancer or certain chronic conditions, including heart or lung disease [4]
- Pregnancy, the postpartum period, and use of estrogen-containing birth control or hormone therapy [2].
- Having a family history of blood clots [4]
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What are the warning signs of a lung blood clot?
Signs of a pulmonary embolism may include shortness of breath, chest pain, or a rapid heartbeat. Symptoms can appear suddenly, although they may also develop more gradually. If you experience possible PE symptoms—especially sudden breathing difficulty or chest pain—seek emergency medical help immediately; do not wait to see whether they pass.[1]
A lung blood clot may have the following symptoms:
- Rapid onset of breathlessness (difficulty breathing)
- Difficulty breathing and pain while breathing
- A faster-than-normal heart rate [1]
- Coughing, occasionally with blood
- Feeling lightheaded or dizzy
How Does a Blood Clot End up in the Lungs?
Often the question arises: if and how fast does a blood clot travel from the leg to the lungs? The clot may develop in a deep leg vein, detach, and travel through the veins to the right side of the heart before entering an artery in the lungs. The timing and symptoms vary: some people develop symptoms within seconds to minutes, while others notice them more gradually over days or weeks. [1]
How Pulmonary Embolism Develops
A pulmonary embolism can occur when part of a clot breaks away and travels through the veins to the right side of the heart. It is then pumped into the pulmonary arteries, where it can become lodged and block blood flow to part of the lungs. A CT pulmonary angiogram (CTPA) is the main imaging test used to diagnose PE.[1]
Screening and Imaging Support
If a doctor suspects a blood clot in the lungs, they may order imaging tests to investigate. The main imaging test is CT pulmonary angiography (CTPA), a specialized CT scan that uses contrast material to show the blood vessels in the lungs and look for a clot. A routine or general CT scan is not automatically equivalent to a CTPA and should not be described as a test that rules out pulmonary embolism.[1] Because suspected PE requires urgent assessment, testing is generally arranged in an emergency or hospital setting so clinicians can interpret the results and begin treatment promptly.
In addition to this, ViaScan also conducts heart scans, whole-body scans, and general CT scans, providing individuals with even more ways to keep up with their overall health. A heart scan (coronary calcium score) looks for calcified plaque in the heart’s arteries [3], and a whole-body scan looks at several areas of the body in one visit. These preventive scans are not used to look for blood clots and are not a substitute for emergency care, so anyone experiencing symptoms of a lung clot should seek immediate medical attention.
Conclusion
Blood clots can end up in the lungs because a clot often starts somewhere else in the body. It can then travel through the bloodstream and lodge in a pulmonary artery. Risk may be higher after surgery or injury, during prolonged immobility, or in people with certain medical conditions or clotting disorders. Spotting the warning signs sooner matters. Getting help fast can make a big difference. If you think you may have a blood clot in your lungs, seek emergency medical attention immediately, and talk with your doctor afterward about your personal risk factors and prevention.
References:
[1] National Heart, Lung, and Blood Institute — Pulmonary Embolism (PE). https://www.nhlbi.nih.gov/health/pulmonary-embolism
[2] National Heart, Lung, and Blood Institute — Women and Venous Thromboembolism (VTE).https://www.nhlbi.nih.gov/health/venous-thromboembolism/women
[3] CardioSmart (American College of Cardiology) — Coronary Artery Calcium (CAC) Scoring. https://cardiosmart.org/cac
[4] Centers for Disease Control and Prevention — Risk Factors for Blood Clots. https://www.cdc.gov/blood-clots/risk-factors/











