International Travel on Anticoagulants: How to Prevent DVT and Stay Safe

Traveling internationally while on blood thinners doesn’t have to be scary-but it does require smart planning. If you’re taking warfarin, rivaroxaban, apixaban, or any other anticoagulant, your biggest worry isn’t the flight itself. It’s the DVT-deep vein thrombosis-that can sneak up during long trips. The risk is real, but it’s manageable. Thousands of people fly, train, and drive long distances every year while safely on anticoagulants. The key isn’t avoiding travel. It’s knowing how to reduce your risk without overdoing it.

Why Travel Increases Your Risk of Blood Clots

Sitting still for more than four hours is the main problem. It doesn’t matter if you’re in economy, business, or first class. What matters is that your leg muscles aren’t moving. When muscles stay relaxed for too long, blood pools in your calves. That’s when clots can form. This isn’t just a myth from old airline warnings. It’s backed by data from the CDC, the American College of Chest Physicians, and the International Air Transport Association. The risk goes up with time: after 4 hours, your chance of a clot starts to rise. After 12 hours, it climbs even higher.

But you’re not just at risk because you’re sitting. If you have other factors-like being over 40, having a BMI over 30, having had surgery in the last three months, or having a history of blood clots-your risk multiplies. People with active cancer, heart failure, or inherited clotting disorders like Factor V Leiden are at especially high risk. The CDC says that for travelers with two or more of these risk factors, the chance of a clot during a long trip jumps to about 1 in 1,000. That’s 5 times higher than for someone with no extra risks.

What You Should NOT Do

A lot of people think they need to take extra medicine before flying. That’s a dangerous mistake. If you’re already on a therapeutic dose of an anticoagulant-meaning your doctor prescribed it to treat or prevent clots-you don’t need to take more. The American College of Chest Physicians says adding aspirin or another blood thinner won’t help. It only raises your risk of bleeding. You could end up in the ER with a stomach bleed or a brain hemorrhage because you thought you were being extra safe.

Don’t skip your dose. This is one of the most common mistakes. Some people think, “I’m flying tomorrow, maybe I should skip my pill to be safer.” That’s the opposite of what you should do. Anticoagulants work by keeping your blood from clotting too easily. If you miss a dose, your blood starts to thicken again. Dr. Susan Coogan at UT Physicians says it plainly: “If you skip doses or stop taking them, your blood can actually become MORE sticky.”

Don’t rely on compression socks you bought online without checking the fit. Many people buy “medical-grade” socks that say 15-20 mmHg but are actually loose or worn out. For them to work, they must fit snugly from your ankle to just below the knee. If they’re too loose, they do nothing. If they’re too tight, they can cut off circulation.

What You SHOULD Do

The best defense is simple, free, and effective: move. Get up and walk every 2 to 3 hours. If you’re on a plane, walk up and down the aisle. On a bus or train, get off at stops and stretch. If you can’t get up, do seated calf exercises every 30 minutes. Tighten your calf muscles, hold for 5 seconds, then relax. Repeat 10 times. Do ankle circles. Point your toes up and down. These movements squeeze the veins in your legs and push blood back toward your heart.

Wear properly fitted compression stockings. Look for below-knee graduated compression socks that provide 15-30 mmHg of pressure at the ankle. These aren’t fashion items-they’re medical devices. Ask your pharmacist or doctor to help you pick the right size. Measure your calf and ankle before buying. A bad fit is worse than no socks at all.

Stay hydrated. Drink water. Not soda, not coffee, not alcohol. Alcohol and sugary drinks dehydrate you. When you’re dehydrated, your blood thickens. That’s the last thing you want. Aim for at least 8 ounces of water every hour during travel. If you’re on a 10-hour flight, that’s 80 ounces. Bring an empty bottle through security and fill it up.

Managing Your Medication While Traveling

If you’re on warfarin, you need to plan ahead. Warfarin’s effect is measured by your INR-a number that tells how long your blood takes to clot. Your doctor should check your INR 1 to 2 weeks before you leave. The target range depends on why you’re on it: 2.0-3.0 for atrial fibrillation, 2.5-3.5 for mechanical heart valves. If your INR is too low, you’re at risk for clots. Too high, and you risk bleeding.

If you’re traveling for more than two weeks and your INR has been unstable, consider a portable INR monitor. The Roche CoaguChek® Mobile costs around $299, and each test strip is about $7.50. It’s worth it if you’ve had trouble keeping your INR steady. You can test yourself in your hotel room and call your doctor if it’s out of range.

Time zones matter. If you’re taking warfarin once a day, take it at the same clock time, not the same circadian time. If you normally take it at 7 p.m. in New York and fly to London (5 hours ahead), take it at 7 p.m. London time. Don’t shift to 2 a.m. your old time. That throws off your schedule and increases the chance of a missed dose.

If you’re on a DOAC-like rivaroxaban, apixaban, or dabigatran-you’re luckier. No blood tests. No food restrictions. Just take it at the same time every day. Rivaroxaban is taken with food, so plan meals around it. If you forget a dose, take it as soon as you remember, unless it’s almost time for the next one. Never double up.

What to Pack

Don’t just throw your pills in your suitcase. Bring your medication in its original bottle with the pharmacy label. Carry a copy of your prescription and a letter from your doctor listing your medications, dosages, and diagnosis. This helps if you’re stopped at customs or need emergency care abroad.

Check if your medication is available where you’re going. Apixaban and rivaroxaban aren’t sold in 32% of low-income countries, according to the WHO. If you’re going somewhere remote, bring extra-enough for your whole trip plus a few extra days. Store DOACs at room temperature. LMWH (like dalteparin) needs refrigeration. If you’re flying with injections, bring a cooler with ice packs and a doctor’s note explaining why you need them.

Pack a small emergency kit: a list of symptoms to watch for, contact info for your doctor back home, and the nearest hospital or clinic at your destination. Know the signs of a clot: swelling in one leg, redness, warmth, or pain. Know the signs of a pulmonary embolism: sudden shortness of breath, sharp chest pain when you breathe, rapid heartbeat.

When to Avoid Travel

The IATA Medical Manual says you can fly if you’ve had a DVT and are now asymptomatic and stable on anticoagulants. That’s good news. But some hospitals, like Cambridge University Hospitals, advise against long trips within four weeks of a clot. There’s no universal rule. If you’ve had a recent clot, talk to your doctor. Don’t rely on airline policies. Your doctor knows your history.

If you’ve had major surgery in the last month-especially under general anesthesia-or if you have active cancer, your risk is high. Even with anticoagulants, your body is still healing. Your doctor might suggest delaying travel. If you must go, they may recommend a single dose of LMWH before departure. Rivaroxaban 10 mg taken one to two hours before travel is another option, but only if your doctor approves it.

What to Do If You Think You Have a Clot

Don’t wait. If you notice swelling in one leg, especially if it’s painful, warm, or red, get medical help immediately. DVT can turn into a pulmonary embolism-a clot that travels to your lungs. That’s life-threatening. If you have sudden shortness of breath, chest pain that gets worse when you breathe, or cough up blood, call emergency services. Don’t try to drive yourself.

Remember: clots can develop up to eight weeks after travel. That’s not a typo. You’re not safe just because you’re home. Keep watching for symptoms for at least two months after your trip.

Bottom Line: You Can Travel Safely

About 4 million Americans are on long-term anticoagulants. Around 65% of them travel each year. Most do it without a problem. The secret isn’t avoiding flights or skipping meds. It’s knowing the risks and taking simple, proven steps: move often, wear the right socks, stay hydrated, take your pills on time, and pack smart. You don’t need to be afraid. You just need to be prepared.