What Are Deep Vein Thrombosis and Pulmonary Embolism?
A blood clot in your leg is a serious medical condition that doctors call deep vein thrombosis, or DVT. This happens when blood thickens and forms a clot inside a vein deep in your leg, usually in the calf or thigh. According to the Centers for Disease Control and Prevention, between 300,000 and 600,000 Americans develop blood clots each year. About one-third of people who have DVT will have long-term problems like pain, swelling, and skin discoloration, even after treatment.
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When a blood clot breaks loose from a leg vein and travels through the bloodstream to the lungs, it can cause a pulmonary embolism, or PE. A pulmonary embolism is particularly dangerous because it can block blood flow to the lungs and make it difficult to breathe. The American Heart Association reports that pulmonary embolism causes about 100,000 deaths per year in the United States. Many of these deaths could be prevented if people understood their risk factors and took steps to reduce their chances of developing clots.
The reason blood clots form is often tied to three main conditions: blood vessel damage, slow blood flow, or changes in blood chemistry. When you sit still for long periods, your blood doesn't circulate as well, which increases clot risk. Injuries or surgery can damage blood vessel walls. Certain medical conditions change how your blood clots. Understanding these basic causes helps you recognize situations where you need to take prevention steps.
Practical Takeaway: Learn the difference between DVT and PE so you can recognize the seriousness of these conditions. DVT is a clot in your leg; PE is when that clot travels to your lungs. Both require medical attention, but PE is life-threatening and needs emergency care.
Common Risk Factors for Leg Blood Clots
Certain situations and health conditions make blood clots more likely to develop. One of the most common risk factors is prolonged immobility. When you sit or lie down for extended periods—such as during long flights, car rides, or bed rest—your leg muscles don't contract enough to push blood back up toward your heart. Research shows that airplane flights lasting more than four hours increase DVT risk. After surgery, especially orthopedic procedures like hip or knee replacement, patients have a significantly higher clot risk for several weeks.
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Age plays a role in clot formation. People over 60 have a higher risk than younger adults, though DVT can happen at any age. Pregnancy and the postpartum period increase risk because hormonal changes affect blood clotting and the growing baby can put pressure on leg veins. Women taking birth control pills or hormone replacement therapy have increased clot risk due to hormonal effects on blood chemistry. Smoking damages blood vessel walls and increases clotting risk, as does obesity, which can put pressure on veins and change how blood flows.
Several medical conditions increase your clot risk significantly. Cancer patients have higher risk, partly due to the disease itself and partly due to treatment. Heart disease, diabetes, and chronic lung disease all increase DVT risk. People with a personal or family history of blood clots have a substantially higher risk of developing them again. Certain genetic conditions affect how the blood clots, making some people naturally more prone to clot formation. Some medications, particularly those containing estrogen and certain cancer drugs, increase clotting risk.
Recent trauma or surgery is another major risk factor. Hip fractures, leg fractures, and major surgeries—especially orthopedic, cancer, or abdominal procedures—put people at high risk for several weeks after the procedure. The trauma causes inflammation and blood vessel damage, while immobility during recovery reduces circulation. This is why doctors often recommend movement and sometimes blood thinners after surgery.
Practical Takeaway: Write down your personal risk factors and review them with your doctor. If you have multiple risk factors, such as a family history of clots plus an upcoming surgery, your doctor may recommend specific prevention measures. Understanding your individual risk helps you know when to be extra vigilant about prevention.
Prevention During Everyday Life
The most basic clot prevention strategy is movement. Regular physical activity keeps your blood circulating and strengthens the muscles in your legs that help push blood back toward your heart. Walking is one of the best activities for clot prevention—even a 30-minute walk several times per week reduces your risk. Swimming, cycling, and other low-impact exercises also work well. Muscle contractions in your legs act like a pump, pushing blood against gravity back up to your heart. When you're sedentary, this pump doesn't work, and blood pools in your leg veins.
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If your job requires long periods of sitting, take frequent movement breaks. Stand up and walk around for a few minutes every hour. Simple leg exercises you can do at your desk also help: lift your legs, march in place, or do calf raises. These muscle contractions improve circulation even while you're seated. Avoid crossing your legs for long periods, as this can compress veins and slow blood flow. If you spend hours on your feet without moving, that's also risky—your legs need actual muscle movement, not just standing.
Staying hydrated helps prevent clots by keeping your blood from becoming too thick. Dehydration causes blood to concentrate, which increases clotting risk. During long travel, especially flights, drink water regularly—aim for about 8 ounces every hour or two. Avoid excessive alcohol and caffeine, as these can have dehydrating effects. Maintaining a healthy weight also reduces clot risk because excess weight puts pressure on veins and changes how blood flows through the legs.
Compression stockings can help prevent blood clots in high-risk situations. These specially designed socks apply graduated pressure that's tighter at the ankle and looser higher up the leg, helping push blood upward. Studies show compression stockings reduce DVT risk by about 50 percent in hospitalized patients and after surgery. You can purchase them at pharmacies or online. For long flights or car rides, wearing compression stockings during travel can reduce your risk.
Elevating your legs when resting also improves blood flow back to your heart. When you sit down to relax, place your feet on an ottoman or chair so your legs are at or above heart level. This uses gravity to help blood return to your heart rather than pooling in your leg veins. This simple position change costs nothing and requires only a few minutes to be helpful.
Practical Takeaway: Build movement into your daily routine through a combination of planned exercise and frequent activity breaks. If you have high-risk factors, add compression stockings during long trips or periods of reduced activity. These simple, no-cost measures significantly reduce your clot risk.
Prevention During Travel and Immobility
Travel poses a special clot risk because you sit still for hours with your legs bent, reducing blood flow. This applies to airplane flights, long car drives, bus trips, or train journeys. Research published in the British Medical Journal found that people who sit still for more than four hours have a clot risk about 26 times higher than people who don't travel. The risk increases with each additional hour of immobility. A cross-country flight lasting six hours or a 12-hour car drive puts you in the high-risk category, regardless of your other health factors.
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Preventing clots during travel starts before you leave home. Wear loose, comfortable clothing that doesn't restrict blood flow. Choose compression stockings rated for travel (typically 15-30 millimeters of mercury of pressure), which are available at drugstores and medical supply stores. They're more comfortable than medical-grade compression stockings and specifically designed for travel situations. Put them on before you leave and wear them throughout your journey.
During travel, follow these movement strategies: get up and walk around every two hours. On planes, walk the aisles. During car trips, stop at rest areas and walk around for five to ten minutes. Even short walking breaks significantly reduce clot risk. While seated, do regular leg exercises: raise and lower your legs, flex your feet by pointing toes and pulling them back, or do calf raises by lifting your heels while keeping toes on the floor. Do these exercises every 30 minutes during long trips. These movements activate the muscle pump in your legs and keep blood circulating.
Hydration during travel is crucial. Airplane cabins have extremely low humidity, and the pressurized environment causes dehydration. Drink water regularly—