Embolism is a serious medical condition where a blockage forms in a blood vessel, usually caused by a blood clot that has traveled from another part of the body. This obstruction prevents blood and oxygen from reaching vital organs and tissues, potentially leading to severe complications or even death if not treated quickly.

Understanding Embolism: A Widespread Health Concern

An embolism occurs when something—most commonly a blood clot—blocks a blood vessel and stops blood from flowing properly. Blood carries oxygen that every cell in your body needs to survive. When a blockage prevents this oxygen from reaching tissues and organs, it can cause serious damage. The substance causing the blockage is called an embolus, and while blood clots are the most frequent culprits, other materials like fat, air bubbles, or even tumor cells can also create these dangerous obstructions.^[1]

What makes embolisms particularly concerning is that the blockage usually doesn’t form where it causes problems. Instead, it starts somewhere else in the body and travels through the bloodstream until it gets stuck in a narrower vessel. This can happen when blood vessels branch off and become smaller, or where fatty deposits have already narrowed an artery. The lungs are the most common destination for these traveling blockages, though they can also lodge in the brain, kidneys, or other organs.^[1]

How Common Are Embolisms?

Embolisms are far from rare—they represent a major global health challenge. In the United States alone, approximately 900,000 people receive a diagnosis of venous thromboembolism (a term that covers blood clots in veins and their complications) each year. This staggering number makes it clear that embolisms affect a significant portion of the population.^[1]

When we look at causes of death related to the heart and blood vessels, pulmonary embolism (a blockage in the lungs) ranks as the third leading cause worldwide. Only strokes and heart attacks claim more lives in this category. This sobering statistic underscores the life-threatening nature of embolisms and the importance of recognizing symptoms early.^[1]

Among the different types of embolisms, those occurring in veins are more common than those in arteries. Most pulmonary embolisms start as blood clots in the deep veins of the legs—a condition called deep vein thrombosis or DVT. When a piece of this clot breaks off and travels to the lungs, it creates a pulmonary embolism that can range from minor to immediately life-threatening.^[3][4]

What Causes Embolisms?

The vast majority of embolisms begin as blood clots that form in the deep veins of the legs. This condition, known as deep vein thrombosis, occurs when blood pools in one area and begins to clot. Sometimes, a portion of this clot breaks free and enters the circulation, traveling through the veins back to the right side of the heart, which then pumps it into the lungs. This is how most pulmonary embolisms develop.^[3][4]

Deep vein thrombosis in the arms can also lead to pulmonary embolism, though this is less common. The fundamental problem is that blood begins clotting when it shouldn’t, creating a solid mass that can obstruct blood flow either where it forms or after it travels to another location.^[4]

While blood clots are the primary cause, embolisms can result from other substances entering the bloodstream. Infections in the heart called infective endocarditis can send infected material through the blood. Heart rhythm problems like atrial fibrillation can allow clots to form in the heart chambers, which then travel to other organs. After a heart attack, clots can form in the damaged heart muscle and later break free.^[1][2]

Traumatic injuries, particularly bone fractures, can release fat particles into the bloodstream, creating what’s called a fat embolism. Medical procedures like liposuction or bone marrow transplants carry similar risks. In pregnant women, a rare but serious complication called amniotic fluid embolism can occur when amniotic fluid escapes into the mother’s circulation. Even air bubbles, particularly in people who dive underwater, can become trapped in blood vessels and cause blockages.^[1][6]

Who Is at Risk?

Certain people face a much higher likelihood of developing embolisms than others. Understanding these risk factors is crucial for prevention and early detection. Physical inactivity tops the list—when you don’t move around much, blood flow slows down, making it easier for clots to form. This is why people who are bedridden due to illness or those who sit for extended periods during long flights or car trips face elevated risk.^[1][5]

Surgery and certain medical procedures significantly increase the risk of embolisms. Operations, especially major ones like hip or knee replacements, can trigger the body’s clotting mechanisms. The combination of tissue damage, reduced movement during recovery, and the body’s natural healing response creates ideal conditions for clots to form.^[1][5]

Age plays an important role—people 65 and older are more susceptible to embolisms. The risk increases with several chronic health conditions, including heart failure, stroke, cancer, and high blood pressure. Cancer is particularly concerning because it can alter the blood’s clotting properties, making clots more likely to form. Some cancers also produce substances that directly promote clotting.^[1][5]

People who use tobacco products face increased risk, as smoking affects blood vessel health and promotes clotting. Those with inherited conditions that make blood clot too easily—called thrombophilia—have a very high risk that often requires lifelong management with blood-thinning medications. Traumatic injuries, particularly those involving severe damage or multiple broken bones, can trigger both clotting and the release of fat particles into the bloodstream.^[1][5][7]

Recognizing the Warning Signs

Embolism symptoms vary greatly depending on where the blockage occurs, how large it is, and whether you have underlying heart or lung disease. Some people experience severe, sudden symptoms, while others notice milder problems that develop gradually over days or weeks. Worryingly, some individuals have no symptoms at all, making the condition even more dangerous.^[1][3]

The most common warning sign is sudden shortness of breath that appears without explanation. This breathlessness can occur even when you’re resting and typically worsens with any physical activity. You might find yourself unable to catch your breath or feel like you can’t get enough air, no matter how hard you try to breathe.^[1][3]

Chest pain is another frequent symptom, often sharp and stabbing. Many people describe it as feeling like a heart attack. The pain usually intensifies when you take a deep breath, cough, or move. This discomfort occurs because the blocked blood vessel prevents oxygen from reaching lung tissue, causing damage and pain. Some people also experience pain in their back, shoulder, neck, or jaw.^[1][3]

Your breathing pattern may change noticeably. You might breathe very rapidly but shallowly, a condition called tachypnea. Your heart may race as it tries to compensate for reduced oxygen levels, leading to tachycardia or a rapid, pounding heartbeat. Some people develop a cough, which may produce bloody mucus—a particularly alarming symptom that requires immediate medical attention.^[1][3]

Low oxygen levels in your blood, called hypoxemia, can cause your skin to appear pale, clammy, or even bluish. You might feel dizzy, lightheaded, or faint. Some people experience anxiety or a sense that something is seriously wrong. In severe cases, you might actually lose consciousness. Other symptoms can include excessive sweating, fever, and swelling in your arms or legs if the original clot formed there.^[1][3]

When an embolism occurs in the brain rather than the lungs, it can cause stroke symptoms like sudden weakness, severe headache, seizures, difficulty speaking, or vertigo. In the abdomen, emboli can cause severe abdominal pain, nausea, and vomiting. A rare type affecting the eye can cause sudden blindness.^[1][6]

Preventing Embolisms: Steps You Can Take

Preventing embolisms involves addressing the risk factors that make blood clots more likely to form. The good news is that many preventive measures are within your control and can significantly reduce your risk. Staying physically active is one of the most effective strategies. Regular exercise keeps blood flowing smoothly through your veins and helps prevent the pooling that leads to clot formation.^[15][17]

When you must sit for long periods—during long flights, car trips, or train rides—take frequent breaks to move around. Aim to stand up and walk at least once every hour or two. If you can’t leave your seat, exercise your leg muscles by pumping your feet up and down, pulling your toes toward your knees and then pointing them down. This simple movement helps push blood through your leg veins back toward your heart.^[15][18]

After surgery or during illness that requires bed rest, try to get up and move as soon as your doctor says it’s safe. Even small amounts of movement can make a big difference. If you absolutely cannot get out of bed, flex your feet and move your legs regularly to maintain blood flow. Your healthcare team may recommend wearing compression stockings—special tight socks that help blood move up from your legs toward your heart.^[15][18]

Maintaining a healthy weight reduces your risk of embolisms and many other health problems. Obesity increases pressure on leg veins and can slow blood flow. If you smoke, quitting is one of the best things you can do for your vascular health. Smoking damages blood vessel walls and makes your blood more likely to clot.^[5][15]

Talk with your doctor about whether hormonal birth control or hormone therapy is safe for you, especially if you have other risk factors for blood clots. There may be alternative options that don’t increase clotting risk. Staying well-hydrated helps keep blood flowing smoothly, particularly important during travel or hot weather.^[5][17]

Getting vaccinated against COVID-19, influenza, and pneumonia helps prevent serious illnesses that could lead to prolonged bed rest or hospitalization—both of which increase embolism risk. If you have a family history of blood clots or a known clotting disorder, make sure your healthcare providers are aware so they can take appropriate precautions during any medical procedures.^[18]

How Embolisms Affect Your Body

Understanding what happens in your body during an embolism helps explain why this condition is so serious. When a blood clot or other material blocks a blood vessel, it prevents blood from flowing past that point. Blood carries oxygen and nutrients that cells need to survive and function. Without this supply, tissues and organs begin to suffer damage almost immediately.^[1][2]

In the lungs, a pulmonary embolism blocks blood flow to sections of lung tissue. The affected area cannot exchange oxygen and carbon dioxide properly, reducing the amount of oxygen entering your bloodstream. This is why shortness of breath is such a prominent symptom. Your heart must work much harder to pump blood through the remaining open vessels, increasing pressure in the pulmonary arteries. This extra strain can lead to heart failure if the blockage is severe or left untreated.^[3][4]

The blocked lung tissue itself suffers injury from lack of oxygen, called a lung infarct. This damaged tissue can cause chest pain and may lead to permanent scarring. In severe cases, large clots can block major pulmonary vessels, preventing the right side of your heart from pumping blood into your lungs at all—a catastrophic situation that can cause sudden death.^[1][4]

When an embolism occurs in an artery supplying the brain, it blocks oxygen delivery to brain tissue, causing a stroke. Brain cells begin dying within minutes of being deprived of oxygen, leading to permanent damage if blood flow isn’t restored quickly. The specific symptoms depend on which part of the brain is affected—loss of speech, paralysis, vision changes, or cognitive problems can all result.^[2][6]

Small emboli might break off repeatedly from a larger clot in a vein, traveling to the lungs in a series of smaller blockages. While each individual embolus might be small, the cumulative effect of multiple clots can be just as dangerous as one large blockage. This pattern explains why some people experience gradually worsening symptoms over several days or weeks rather than a sudden catastrophic event.^[1][9]

Blood pressure throughout your body can drop dangerously low if a large embolism prevents adequate blood circulation. Your body tries to compensate by increasing heart rate and breathing rate, but these mechanisms may not be enough if the blockage is severe. Organs throughout your body can suffer from inadequate oxygen delivery, leading to multiple organ dysfunction in the worst cases.^[1][4]