Deep Vein Thrombosis (DVT) and Flying: What Travellers Need to Know

Long haul flights carry a small but real risk of deep vein thrombosis (DVT), a blood clot that forms in a deep vein, usually in the leg. It’s a well known travel health concern, and one that’s easy to reduce with a few simple precautions.

What Is DVT, and Why Does Flying Raise the Risk?

DVT happens when blood flow slows down enough for a clot to form, usually in the calf or thigh. Several things about flying contribute to this:

• Prolonged immobility. Sitting still for hours reduces blood flow in your legs.
• Dehydration. Cabin air is very dry, and this can thicken your blood slightly.
• Lower cabin pressure. This has a small additional effect on circulation.
  
  

The risk is generally linked to flight duration. Flights over about 4 hours carry more risk than shorter ones, and the risk continues to rise with longer flights.

Who’s at Higher Risk?

Anyone can develop DVT during a long flight, but risk is higher if you:

• Have had DVT or a blood clot before
• Have a family history of blood clots
• Are pregnant or recently gave birth
• Take the combined contraceptive pill or hormone replacement therapy
• Have had recent surgery, particularly on your legs or abdomen
• Have certain cancers, or are undergoing cancer treatment
• Are significantly overweight
• Are over 60
• Have a known clotting disorder
  
  

If more than one of these applies to you, it’s worth discussing your travel plans with a GP or pharmacist before a long flight.

Recognising the Symptoms

DVT symptoms can appear during your flight, or in the days afterward. Look out for:

• Swelling in one leg (usually just one side)
• Pain or tenderness, often in the calf
• Warm skin over the affected area
• Red or discoloured skin
  
  

A DVT can potentially travel to your lungs, causing a pulmonary embolism, a medical emergency. Signs include sudden breathlessness, chest pain (especially when breathing in), and coughing up blood. This needs immediate emergency medical attention.

How to Reduce Your Risk

Before you fly:

• If you’re at higher risk, ask your GP or pharmacist about compression stockings or other precautions before booking a long haul flight.
  
  

During the flight:

• Move around the cabin every hour or two, if possible.
• Do simple seated exercises: flex your ankles, rotate your feet, and stretch your calf muscles regularly.
• Stay well hydrated, drink water regularly throughout the flight.
• Avoid excessive alcohol, which contributes to dehydration.
• Wear loose, comfortable clothing.
• Consider graduated compression stockings, particularly for flights over 4 hours if you have any risk factors.
  
  

After you land:

• Keep moving once you arrive, a short walk helps restore normal circulation.
• Stay alert for symptoms over the following 1 to 2 weeks, since DVT can develop after you’ve landed.
  
  

When to Seek Medical Help

If you notice swelling, pain, or warmth in one leg after a flight, see a doctor promptly, don’t wait to see if it improves on its own. If you develop sudden breathlessness or chest pain, treat this as a medical emergency and seek immediate help.

It’s also worth mentioning any long haul flights you’ve taken in the past few weeks to a doctor if you develop unexplained leg swelling or breathlessness, even if the connection isn’t obvious to you at the time.

This article is for general information only. It’s not personal medical advice. If you have risk factors for DVT and are planning a long flight, please speak to your GP or pharmacist beforehand for personalised advice. Book consultation with us