What Causes Blood Clots in the Lungs? Risk Factors and Prevention

Blood clots in the lungs, known medically as pulmonary embolism, usually happen when a clot forms elsewhere in the body and travels to the lungs. Understanding the symptoms, risk factors, and prevention steps can help people seek timely care and lower their risk.

Overview

Blood clots in the lungs are called pulmonary emboli, and the condition is known as pulmonary embolism. This happens when a clot blocks one of the blood vessels in the lungs, reducing blood flow. In many cases, the clot starts in a deep vein in the leg or pelvis and then travels through the bloodstream to the lungs.

A pulmonary embolism can range from small to severe. Small clots may cause mild symptoms or sometimes none at all, while larger clots can put strain on the heart and lungs. Because the lungs help deliver oxygen to the body, any blockage in their blood supply can affect breathing and circulation.

Blood clots in the lungs are considered a medical condition that needs prompt evaluation. Early diagnosis and treatment can lower the risk of complications and help protect lung and heart function. Many people recover well, especially when the problem is recognized and treated quickly.

Symptoms of Blood Clots in the Lungs

Symptoms of blood clots in the lungs can vary depending on the size of the clot and how much of the lung is affected. The most common symptom is sudden shortness of breath. Some people notice chest pain that may feel sharper when taking a deep breath, coughing, or moving.

Other symptoms may include a fast heartbeat, dizziness, fainting, sweating, anxiety, or coughing. In some cases, the cough may bring up blood-streaked mucus. These symptoms do not always mean pulmonary embolism, but they should not be ignored, especially if they start suddenly.

Some people also have signs of a deep vein clot before the clot reaches the lungs. These can include swelling, pain, warmth, or redness in one leg, often in the calf. This earlier condition is called deep vein thrombosis, and it is closely linked to pulmonary embolism.

• Sudden shortness of breath
• Chest pain, especially with breathing
• Rapid heart rate
• Cough, sometimes with blood
• One-sided leg swelling or pain

What Causes Blood Clots in the Lungs?

The most common cause of blood clots in the lungs is a clot that forms in a deep vein and then breaks loose. This is why pulmonary embolism and deep vein thrombosis are often discussed together. The combined condition is known as venous thromboembolism.

Clots are more likely to form when blood flow becomes slow, when the lining of a blood vessel is injured, or when the blood is more likely to clot than usual. These three factors are often described together in medicine because they explain why some situations increase risk so strongly.

For example, sitting still for long periods can slow blood flow in the legs. Surgery or injury can affect blood vessels and trigger clot formation. Some medical conditions and inherited traits can make the blood clot more easily than normal.

In a smaller number of cases, clot-like blockages in the lungs may be related to other rare causes, but a true pulmonary embolism is usually due to a blood clot from the veins. Doctors focus on finding the source of the clot so they can treat it and help prevent another event.

Risk Factors

Many factors can raise the risk of blood clots in the lungs. Long periods of immobility are a common cause. This can happen during bed rest, recovery after surgery, long hospital stays, or long-distance travel. When the leg muscles are inactive, blood may pool in the veins and clot more easily.

Recent surgery, trauma, and cancer are also important risk factors. Certain cancers and cancer treatments can make the blood more prone to clotting. People with heart disease, obesity, smoking history, or advancing age may also face a higher risk.

Hormonal factors matter as well. Pregnancy, the weeks after childbirth, and the use of estrogen-containing medications such as some birth control pills or hormone therapy can increase clot risk. A personal or family history of clots may suggest an inherited clotting tendency.

Risk can rise when several factors happen together. For example, a person who has surgery, is less mobile afterward, and already has a family history of clots may need closer monitoring and preventive treatment. Doctors may also investigate for related conditions such as pulmonary hypertension if there are concerns about lasting pressure changes in the lung circulation after a clot.

How Blood Clots in the Lungs Are Diagnosed

Diagnosis starts with a medical history, symptom review, and physical examination. Doctors ask about sudden shortness of breath, chest pain, leg symptoms, recent travel, surgery, pregnancy, medication use, and previous clots. Because symptoms can overlap with pneumonia, asthma, heart problems, or lung cancer, testing is important to confirm the cause.

Common tests may include a blood test called D-dimer, which can help show whether clotting activity may be present. Imaging is often needed to make the diagnosis. A CT pulmonary angiogram is a commonly used scan that can show clots in the lung arteries. If CT is not suitable, a ventilation-perfusion scan may be used in some cases.

Doctors may also check the legs with ultrasound to look for deep vein thrombosis. Additional tests such as oxygen measurement, chest X-ray, electrocardiogram, or echocardiogram can help assess how the clot is affecting the heart and lungs. These tests also help rule out other causes of symptoms.

Prompt and accurate diagnosis matters because treatment decisions depend on clot size, location, and the patient’s overall stability. The care team also considers whether the person has a low, moderate, or high risk of complications.

Treatment Options

The main treatment for blood clots in the lungs is anticoagulation, often called blood-thinning treatment. These medicines do not dissolve the clot immediately, but they help prevent the clot from growing and reduce the chance of new clots forming. Over time, the body can gradually break down the clot on its own.

Some people may need oxygen, pain relief, or hospital monitoring, depending on symptoms and overall health. In more serious cases, treatment may involve medicines that actively break down clots or procedures to remove them. These options are usually reserved for selected situations where the clot is large or causing major strain on the heart.

If a person cannot safely take blood thinners, doctors may consider other approaches, such as a device placed in a large vein to help stop clots from reaching the lungs. When needed, specialists may use advanced tests or procedures to guide care, including interventional radiology techniques in appropriate cases.

Follow-up care is an important part of treatment. Doctors monitor for side effects, decide how long anticoagulation should continue, and look for underlying causes. In complex cases, assessment by specialists in cardiology and respiratory medicine may be helpful. Acibadem International’s multidisciplinary specialists and JCI-accredited hospitals diagnose and treat pulmonary embolism for international patients.

Prevention and Self-care

Prevention is especially important for people with known risk factors. Regular movement helps keep blood flowing in the legs. During long trips, it can help to stand up, stretch, or walk when possible. Flexing the ankles and calves while seated may also support circulation.

After surgery or illness, following the care team’s advice about getting out of bed, wearing compression stockings if prescribed, and taking preventive blood thinners when recommended can lower the risk of clots. Staying hydrated is also useful, especially during travel or recovery, although hydration alone cannot prevent all clots.

Managing overall health may reduce long-term risk. This includes stopping smoking, maintaining a healthy weight, staying physically active, and working with a doctor to control chronic conditions. People who have had blood clots before should discuss future pregnancy, surgery, and travel plans with their healthcare team.

Some people at high risk may benefit from expert review before major surgery or during cancer treatment. In selected situations, doctors may coordinate prevention with specialists involved in vascular surgery or other supportive care teams.

When to See a Doctor

Anyone with sudden unexplained shortness of breath, chest pain, fainting, or coughing up blood should seek urgent medical attention. These symptoms can have several causes, but pulmonary embolism is one of the conditions that doctors need to rule out quickly.

Medical advice is also important for people who notice signs of a possible leg clot, such as swelling or pain in one calf, especially after surgery, travel, or prolonged bed rest. Treating a deep vein clot early may help prevent it from reaching the lungs.

People with a history of clots should speak with a doctor before long flights, planned operations, or starting hormone-based medicines. Knowing personal risk can make prevention more effective and reassuring. A qualified healthcare professional can recommend the safest next steps based on individual needs.

Frequently asked questions

Are blood clots in the lungs the same as deep vein thrombosis?

No. Deep vein thrombosis is a clot that usually forms in a deep vein of the leg or pelvis, while a pulmonary embolism happens when a clot travels to the lungs. The two conditions are closely related and often considered part of the same disease process.

Can a blood clot in the lungs go away?

Yes, the body can gradually break down a clot over time, especially with proper treatment. Blood-thinning medicines help prevent the clot from getting larger and reduce the risk of new clots. Follow-up is important to make sure recovery is progressing safely.

What does a blood clot in the lung feel like?

Many people describe sudden shortness of breath, chest pain that may worsen with deep breathing, or a fast heartbeat. Some also feel lightheaded, anxious, or have a cough. Symptoms vary, so any sudden breathing or chest symptoms should be assessed by a doctor.

Who is most at risk of pulmonary embolism?

People at higher risk include those who have recently had surgery, been immobilized, traveled for long periods, or had cancer. Pregnancy, smoking, obesity, estrogen-containing medicines, and inherited clotting disorders can also increase risk. Risk is often higher when several factors occur together.

Can walking help prevent blood clots?

Yes, regular movement and walking can help reduce the risk by improving blood flow in the legs. This is especially useful during recovery, long trips, or sedentary periods. However, people at higher risk may still need medical prevention measures such as compression or medication.

Is pulmonary embolism treatable?

Yes, pulmonary embolism is treatable, and many people recover well with timely care. Treatment usually involves anticoagulant medicines, though some cases need more advanced procedures. The best approach depends on the clot’s size, location, and the person’s overall health.

References

• World Health Organization
• Centers for Disease Control and Prevention
• National Heart, Lung, and Blood Institute
• American Society of Hematology
• European Society of Cardiology

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.