International Travel on Anticoagulants: How to Stay Safe and Prevent Blood Clots

Planning an international trip while on blood thinners? You’re not alone. Millions of people around the world take anticoagulants for conditions like atrial fibrillation, deep vein thrombosis, or artificial heart valves-and many of them fly, train, or drive long distances every year. The good news? Traveling while on these medications is generally safe-if you know what to do. The bad news? Skipping a dose, ignoring leg swelling, or drinking too much wine on the plane can turn a routine trip into a medical emergency.

Why Travel Increases Your Risk of Blood Clots

Sitting still for hours is the real enemy. It doesn’t matter if you’re in first class or economy. What matters is that your legs aren’t moving. When blood pools in your lower legs, it can start to clot. That’s called deep vein thrombosis, or DVT. If that clot breaks loose and travels to your lungs, it becomes a pulmonary embolism (PE)-a life-threatening event.

The CDC says the risk of travel-related DVT doubles after four hours of continuous sitting. For someone with no extra risk factors, the chance is low-about 1 in 4,656 flights. But if you’re over 40, have a BMI over 30, had surgery recently, have cancer, or have had a blood clot before? Your risk jumps to 1 in 1,000. That’s not a small number. And if you’re on anticoagulants but skip a dose? You’re essentially turning off your body’s safety net.

What Your Doctor Wants You to Know About Medication

If you’re on warfarin, your INR (a blood test that measures how long it takes your blood to clot) needs to be checked before you leave. Aim for a result between 2.0 and 3.5, depending on why you’re taking it. If your INR is too low, you’re at risk for clots. Too high? You risk bleeding. Don’t wait until you’re at the airport to find out.

For people on DOACs-drugs like rivaroxaban, apixaban, or dabigatran-there’s no need for regular blood tests. That’s one reason they’re easier to manage while traveling. But here’s the catch: DOACs cost a lot more. Rivaroxaban runs around $575 for a 30-day supply. Warfarin? About $4. If cost is an issue, stick with warfarin-but only if you can manage the testing.

Never skip a dose. Even one missed pill can make your blood start clotting again. Dr. Susan Coogan at UT Physicians says it plainly: “If you stop taking your blood thinner, your blood becomes MORE sticky.” That’s not a myth. It’s science.

Time zones? They matter. If you’re flying across multiple zones, take your medication at the same clock time-not the same time of day. If you usually take warfarin at 6 p.m. Pacific Time and you land in London, take it at 6 p.m. London time, not 6 p.m. your old time. That keeps your levels steady.

What to Pack: More Than Just Pills

Your suitcase needs more than clothes and chargers. Here’s what to bring:

• A printed list of all your medications: names, doses, and your doctor’s contact info
• Your most recent INR result (if on warfarin)
• Compression stockings (15-30 mmHg pressure) that fit properly
• A portable INR monitor like the Roche CoaguChek® Mobile if you’re traveling longer than two weeks and your INR is unstable
• Enough medication for the entire trip plus at least 7 extra days
• A note from your doctor explaining your condition and medications (helpful if customs asks)

Don’t assume your meds will be available abroad. Apixaban, for example, isn’t sold in 32% of low-income countries. If you’re going somewhere remote, bring extra. And if you’re on LMWH (like dalteparin), remember-it needs refrigeration. That’s a nightmare on a 12-hour flight with no fridge access.

How to Move While You Travel

Movement is your best defense. You don’t need to run laps in the airport. Just move your legs.

• Do calf raises every 30 minutes: lift your heels, hold for 3 seconds, lower. Repeat 10 times.
• Point and flex your toes. Do this while watching a movie or scrolling on your phone.
• Walk the aisle every 2-3 hours. Even 5 minutes helps.
• If you’re driving, stop every 2 hours. Walk around the gas station. Stretch your legs.
• Choose an aisle seat. It’s easier to get up without disturbing others.

Compression stockings aren’t optional for high-risk travelers. They squeeze your legs just enough to keep blood moving. Make sure they’re the right size-too loose, and they don’t work. Too tight, and they cut off circulation. Ask your pharmacy for a professional fitting.

What to Drink (and What to Avoid)

Hydration is critical. Dehydration thickens your blood. That’s bad news when you’re already at risk for clots.

• Drink water. A lot of it. Aim for at least 8 ounces every hour during travel.
• Avoid alcohol. It dehydrates you and can interfere with warfarin.
• Skip sugary sodas and energy drinks. They don’t hydrate-they just add sugar and caffeine.
• Don’t rely on airline drinks. They’re often watered down or served in tiny portions.

If you’re on warfarin, keep your vitamin K intake steady. That means don’t suddenly start eating giant salads or kale smoothies every day. It won’t cause a clot, but it can make your INR swing unpredictably.

Warning Signs: Don’t Ignore These

Most people with DVT don’t feel anything at first. But when symptoms appear, they’re clear:

• Swelling in one leg (72% of DVT cases show this)
• Pain or tenderness in the calf, especially when standing or walking
• Redness or warmth in the affected area
• Sudden shortness of breath
• Chest pain that gets worse when you breathe deeply
• Fast heartbeat or dizziness

If you feel any of these, get help immediately. DVT can develop up to eight weeks after travel. That means your risk doesn’t end when you land.

When to Avoid Travel Altogether

Some situations are too risky to ignore:

• Within four weeks of a new DVT or PE diagnosis
• If you’re still in pain, swollen, or short of breath
• If you’ve had major surgery in the last month
• If you have active cancer and are newly diagnosed
• If you’re not yet stable on your anticoagulant dose

The IATA says you can fly once you’re asymptomatic and stable on anticoagulants-but doesn’t say how long “stable” means. Cambridge University Hospitals says wait four weeks. Your doctor should decide based on your history. Don’t let airline policies override medical advice.

What’s Changing in 2026

The medical world is catching up. The MARVEL trial, which started in 2022, is testing whether a single daily dose of rivaroxaban before long flights can safely prevent clots in high-risk travelers. Results are expected by late 2024. If proven effective, this could become a new standard-especially for people with cancer or a history of unprovoked clots.

Meanwhile, more airlines are starting to offer compression sock sales on board. Some airports now have walking paths designed for long layovers. These are small steps-but they matter.

Final Checklist Before You Go

• ✅ See your doctor 2-4 weeks before departure
• ✅ Get your INR checked (if on warfarin)
• ✅ Confirm your meds are available at your destination
• ✅ Pack extra pills (7+ days beyond your trip)
• ✅ Buy properly fitted compression stockings
• ✅ Plan to move every 2-3 hours
• ✅ Carry emergency contact info for local hospitals
• ✅ Know the signs of bleeding and clotting
• ✅ Never skip a dose

Traveling on blood thinners isn’t about fear. It’s about preparation. You’ve already managed a chronic condition. Now you’re just adding a few smart habits to your routine. Do this right, and you can fly to Tokyo, hike in Peru, or road-trip across Europe-without a second thought about your blood.