Preventing blood clots in your legs comes down to keeping your blood moving, staying hydrated, and managing the specific risk factors that apply to your situation. Deep vein thrombosis (DVT) forms when blood pools in the deep veins of your legs, thickens, and clots. Three conditions make this more likely: sluggish blood flow, blood that clots too easily, and damage to the walls of your veins. You can directly influence at least two of those three factors with everyday habits.
Why Blood Clots Form in the Legs
Your leg veins work against gravity to push blood back toward your heart. When you sit or stand still for long stretches, that return flow slows dramatically, and blood starts pooling in the calves and thighs. This stagnant blood is more prone to clotting. At the same time, anything that makes your blood thicker or stickier, like dehydration or certain medical conditions, tips the balance further toward clot formation. Vein wall damage from surgery, injury, or even an IV line provides the final ingredient.
You don’t need all three factors present at once. A long flight combined with mild dehydration can be enough. So can major surgery followed by days in bed. The goal of prevention is to interrupt as many of these factors as possible.
Move Regularly Throughout the Day
Physical movement is the single most effective thing you can do. Walking contracts your calf muscles, which act as a pump to squeeze blood upward through your veins. This is why getting up and moving has been a cornerstone of clot prevention since the 1950s, when early ambulation after surgery became standard medical advice.
If you work at a desk, aim to get up and walk for a few minutes every hour. A 2024 University of Sydney study found that sitting for more than 10 hours a day increased both cardiovascular and circulatory disease risk. Interestingly, the same study found that simply standing more (such as using a standing desk) did not reduce cardiovascular risk and could actually increase the risk of circulatory problems like varicose veins and DVT. The key distinction is active movement, not just changing your static position. Walking, even briefly, is far more protective than standing in place.
If you can’t leave your seat, calf exercises work surprisingly well. Raise and lower your heels while keeping your toes on the floor, then reverse it by raising your toes while your heels stay planted. Tighten and release your leg muscles repeatedly. These simple contractions keep blood from stagnating in your lower legs.
Preventing Clots During Travel
Flights and long car rides are a well-known trigger because you’re sitting in a cramped position for hours, often slightly dehydrated from cabin air or skipping water to avoid bathroom stops. The CDC recommends choosing an aisle seat when possible so you can get up and walk every two to three hours. On a road trip, schedule stops at the same interval.
While seated, rotate through the calf exercises described above every 20 to 30 minutes. Avoid crossing your legs, which further restricts blood flow. Drink water consistently throughout the trip rather than relying on coffee or alcohol, both of which can contribute to dehydration. Wearing moderate-compression stockings (15 to 20 mmHg) during flights longer than four hours adds another layer of protection, especially if you have additional risk factors like a history of DVT or recent surgery.
Stay Hydrated to Keep Blood Flowing
Dehydration thickens your blood by reducing its water content. This increased viscosity makes clotting more likely and forces your cardiovascular system to compensate: blood vessels constrict, heart rate rises, and circulation slows. All of these responses push conditions toward clot formation.
There’s no magic number of glasses per day that prevents DVT specifically, but consistent fluid intake throughout the day keeps blood volume and viscosity in a healthy range. Pay extra attention during travel, after exercise, in hot weather, and if you’re recovering from illness. If your urine is dark yellow, you’re likely not drinking enough.
How Compression Stockings Help
Graduated compression stockings apply the most pressure at the ankle and gradually decrease pressure moving up the leg, which mimics the natural pumping action of your calf muscles and helps push blood upward. They come in several pressure levels:
- Mild (8 to 15 mmHg): light support for minor swelling and leg fatigue
- Moderate (15 to 20 mmHg): the standard recommendation for DVT prevention during travel, mild varicose veins, and general swelling
- Firm (20 to 30 mmHg): used for moderate swelling, varicose veins, and post-surgical recovery
- Extra firm (30 to 40 mmHg): reserved for severe venous disorders and advanced DVT cases
For general prevention, the moderate range is what most people need. You can buy these over the counter at pharmacies. Firm and extra-firm stockings typically require a prescription and proper fitting. The stockings need to fit correctly to work. Too loose and they won’t provide meaningful compression; too tight and they can actually restrict circulation. Knee-high stockings are sufficient for most prevention purposes.
After Surgery or Hospitalization
Surgery is one of the highest-risk periods for DVT, particularly orthopedic procedures on the hips or knees and any operation that keeps you in bed for more than a few days. The combination of immobility, possible vein damage during the procedure, and the body’s natural increase in clotting factors after tissue injury creates near-ideal conditions for a clot.
Your surgical team will likely use a combination of prevention strategies: compression devices that inflate and deflate around your calves while you’re in bed, blood-thinning medications, and early walking. The most important thing you can do is get moving as soon as your medical team clears you. Even short walks down the hospital hallway make a measurable difference. At home, continue walking regularly and wearing compression stockings for as long as recommended, which is often several weeks after major joint surgery.
Dietary Considerations
If you take a blood thinner that works by blocking vitamin K (warfarin is the most common), your diet plays a direct role in how well that medication works. Vitamin K, found in leafy greens like spinach, kale, and broccoli, promotes clotting. The issue isn’t eating these foods; it’s eating wildly different amounts from day to day. Fluctuating vitamin K intake is one of the main causes of unstable blood-thinner control.
Research from the Leiden anticoagulation clinic found that patients who took a small, consistent daily vitamin K supplement alongside their medication actually had more stable anticoagulation than those who didn’t. The takeaway: consistency matters more than avoidance. Eat a steady amount of green vegetables rather than having none for a week and then a large salad. If you’re on a newer type of blood thinner (which works through a different mechanism), vitamin K intake is generally not a concern.
Know Your Personal Risk Factors
Some people need to be more aggressive about prevention than others. The factors that raise your risk include active cancer, recent surgery or prolonged bed rest (more than three days), a leg that’s been in a cast, a personal or family history of blood clots, pregnancy, use of hormonal birth control or hormone replacement therapy, obesity, and smoking. The more of these that apply to you, the more seriously you should take every prevention strategy on this list.
Certain signs warrant prompt attention: swelling in one leg (not both), pain or tenderness in the calf that feels like a cramp but doesn’t go away, warmth in the affected area, and skin that looks red or discolored. A classic warning sign is calf swelling that measures more than 3 centimeters larger than the other leg. DVT in one leg rarely causes identical symptoms in both legs, so asymmetry is a key signal. If a clot breaks loose and travels to the lungs, it causes sudden shortness of breath, chest pain, and rapid heartbeat, which is a medical emergency.
Putting It All Together
The most effective prevention strategy layers multiple approaches. Walk or do calf exercises throughout the day rather than simply standing or sitting. Stay consistently hydrated. Wear moderate-compression stockings during long travel or periods of reduced mobility. After surgery, follow your recovery team’s guidance on early movement and any prescribed blood thinners. If you’re on warfarin, keep your green-vegetable intake steady from day to day rather than cutting it out entirely. And if you carry multiple risk factors, talk with your doctor about whether a short course of preventive medication makes sense before high-risk situations like surgery or extended travel.