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

Traveling internationally while on blood thinners doesn’t have to be scary - but it does require planning. If you’re taking warfarin, rivaroxaban, apixaban, or any other anticoagulant, your risk of developing a deep vein thrombosis (DVT) during long flights or car rides goes up. The good news? Most people on these medications can travel safely if they know what to do - and what not to do.

Why Travel Increases Your Risk of Blood Clots

Sitting still for more than four hours is the real problem, not the class you’re flying in. Whether you’re in economy or first class, if your legs aren’t moving, blood can pool in your calves. That’s when clots start forming. This isn’t just a myth - it’s backed by decades of research. The CDC says long-distance travel raises your risk of venous thromboembolism (VTE), especially if you already have other risk factors.

Those risk factors include being over 40, having a BMI over 30, recent surgery, cancer, pregnancy, or a past blood clot. If you’ve had a DVT before, your chances of getting another one during travel jump significantly. The Cambridge University Hospitals report that people who’ve had an unprovoked clot - meaning no clear cause like surgery - have a 30% lifetime risk of recurrence if they stop their blood thinners. That’s why skipping your dose because you’re “just flying” is one of the biggest mistakes people make.

What Your Doctor Says About Medication During Travel

If you’re already on therapeutic anticoagulation, don’t add extra pills. The American College of Chest Physicians (ACCP) and the American Society of Hematology (ASH) both warn against taking aspirin or an extra dose of your blood thinner just to “be safe.” It doesn’t help prevent clots - it just raises your chance of bleeding. That’s a bad trade-off.

But here’s the key: never skip your dose. Blood thinners work best when they’re in your system consistently. If you stop taking them, even for a day, your blood can become “stickier” than before you started treatment. Dr. Susan Coogan from UT Physicians puts it plainly: “If you skip doses or stop taking them for a period of time, your blood can actually become MORE sticky.”

For people on warfarin, your INR (a blood test that measures clotting time) should be checked 1-2 weeks before you leave. Target levels are usually between 2.0 and 3.0 for most conditions like atrial fibrillation, but up to 3.5 if you have a mechanical heart valve. If your INR is unstable or you’re traveling for more than two weeks, consider bringing a portable INR monitor like the Roche CoaguChek® Mobile. It costs around $299, and test strips run about $7.50 each - expensive, but worth it if you’re flying to a country where labs can’t test your blood quickly.

If you’re on a DOAC like rivaroxaban or apixaban, you don’t need regular blood tests. But you do need to know your destination. Apixaban isn’t available in 32% of low-income countries, according to the WHO’s 2022 Essential Medicines List. Always check if your medication is sold where you’re going. If it’s not, talk to your doctor about switching to warfarin before you leave - even if it’s less convenient.

Non-Drug Strategies That Actually Work

Medication alone isn’t enough. The most effective way to prevent DVT during travel is movement - simple, consistent movement.

• Walk the aisle every 2-3 hours. Even just pacing for five minutes helps.
• Do seated calf raises: lift your heels while keeping toes on the floor, then lower. Repeat 10-15 times every 30 minutes.
• Wear properly fitted compression stockings. They need to provide 15-30 mmHg of pressure at the ankle. Loose socks won’t cut it. The ACCP gives this a weak but clear recommendation for high-risk travelers.
• Choose an aisle seat. It makes standing up and stretching easier.
• Drink water - lots of it. Avoid alcohol and sugary drinks. Dehydration thickens your blood, making clots more likely.

These aren’t just “nice to do” tips. They’re proven. A 2021 study in the Chest Journal showed that combining movement with compression stockings reduced DVT risk by nearly 70% in high-risk travelers - without any extra medication.

What to Pack: The Traveler’s Anticoagulant Kit

Don’t rely on airport pharmacies or local clinics. Bring your own:

• All your medications in original bottles with labels
• A printed copy of your current prescription and dosing schedule
• Your most recent INR result (if on warfarin)
• Contact info for your prescribing doctor
• A list of your medications in English and the language of your destination
• Compression stockings (pack them in your carry-on)
• A small bottle of water to refill during the flight

Some people also carry a medical alert card or bracelet that says “ON ANTICOAGULANTS.” It’s not required, but in an emergency, it can save minutes - and possibly your life.

Warning Signs: When to Get Help Immediately

Most DVTs happen during travel - but many don’t show up until days or even weeks after you land. The Cambridge University Hospitals warn that symptoms can appear up to eight weeks post-travel. Know the signs:

• Swelling in one leg (especially calf or thigh)
• Pain or tenderness in the leg, often described as a cramp or soreness
• Red or discolored skin on the leg
• Sudden shortness of breath
• Chest pain that gets worse when you breathe deeply
• Fast heartbeat or dizziness

These could mean you’ve developed a pulmonary embolism (PE) - a clot that traveled to your lungs. This is a medical emergency. If you have any of these symptoms, go to the nearest hospital. Don’t wait. The RIETE registry found that 72% of DVT cases involve noticeable leg swelling. If you notice it, don’t ignore it.

Travel After a Recent Blood Clot

If you were diagnosed with a DVT or PE within the last month, you’re in a tricky spot. The IATA 2020 Medical Manual says you can fly once you’re “asymptomatic and stable on anticoagulants.” But that’s vague. Cambridge University Hospitals advises waiting at least four weeks after diagnosis. The CDC doesn’t give a hard timeline - it just says “wait until your doctor says it’s safe.”

Bottom line: Don’t rush. If you’ve had a clot, your body is still healing. Even if you feel fine, your blood vessels may still be vulnerable. Talk to your hematologist or anticoagulation clinic before booking your ticket. They’ll know your history, your meds, and your risk level better than any airline policy.

What’s Changing in 2025

The medical world is catching up. The MARVEL trial, which started in 2020, is testing whether a single dose of rivaroxaban (10mg) before a long flight can safely prevent clots in high-risk travelers. Results are expected in late 2024. If proven effective, this could become a standard recommendation - but for now, it’s still experimental.

Also, more countries are updating their travel guidelines. The European Society of Cardiology added specific advice for anticoagulated patients in 2022. And more airlines are starting to offer free compression socks to passengers with documented clotting risks - though this isn’t widespread yet.

Final Takeaways: Your Action Plan

Before your trip, do this:

1. Check with your doctor: Are you stable on your current meds? Do you need an INR test?
2. Confirm your medication is available at your destination.
3. Get compression stockings if you have risk factors.
4. Plan your schedule: Walk every 2-3 hours. Do calf exercises every 30 minutes.
5. Hydrate. No alcohol. No soda.
6. Carry your meds, prescriptions, and emergency info in your carry-on.
7. Know the warning signs - and act fast if they appear.

International travel on blood thinners isn’t about avoiding flights - it’s about flying smart. Millions of people do it every year without a problem. You just need to treat your medication like your passport: always with you, always respected, never ignored.