Phoebe Slim
Author: Phoebe Slim, Marketing Executive

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Top tips for flying safely and avoiding Deep Vein Thrombosis (DVT)

When taking a long-haul flight, most of us are aware these days of the potential risk of deep vein thrombosis (DVT), and the importance of moving around every now and then to boost blood flow. 

DVT can affect anybody, but it becomes more common with age. Things that can increase the likelihood of having DVT include obesity, pregnancy, smoking and periods of inactivity (such as being bed-ridden following illness or surgery). Having other health conditions can also mean you’re prone to DVT – including some cancers and heart disease. Taking certain medications, like some types of oral contraceptive pills, can also contribute.

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What is DVT?

Deep Vein Thrombosis (also known as DVT) is a blood clot that forms in the deep veins of the body, most commonly in the calf muscle of the leg. Sometimes there are no symptoms, and clots can be treated with anticoagulant medicines (drugs that reduce clotting). 

There are some warning signs, such as pain, swelling, a heavy ache and redness/warmth of the skin in the affected area. Speedy treatment is crucial, as if it’s left untreated deep vein thrombosis can lead to a much more serious condition called a pulmonary embolism. This happens when a blood clot finds its way to the chest, blocking vital blood vessels in the lungs. A pulmonary embolism can be fatal, so it’s vital to seek medical help immediately if you’re concerned.

Thankfully, there’s a lot that can be done to prevent DVT, and having a history of the condition does not automatically mean flights are off the agenda, as Professor Mark Whiteley of The Whiteley Clinic one of the world’s leading venous experts, explains.

Why does flying cause DVT?

“Flying is definitely associated with deep vein thrombosis, and much research has been done on this subject,” says Professor Whiteley, who points out that it is flights over four hours that are linked with a “significant risk”.

“The two main known reasons are the inactivity due to sitting still for long periods of time, and secondly the fact that the air is thinner at altitude. This means there are less oxygen molecules in the air, and so there is less oxygen in the bloodstream. This can affect the lining of the vein walls, predisposing to a DVT.”

How long after a flight can DVT occur?

A deep vein thrombosis blood clot can develop anytime from a few days to a few weeks after a flight – usually after a long-haul journey. However, if you’re active during your flight and in the subsequent weeks, these blood clots can break up naturally.


I had DVT - is it safe to fly again?

Hopefully yes – but you’ll need to speak with your doctor, and possibly take extra precautions. 

“This question is not simple to answer as it is dependent on a number of factors, such as how long ago the first DVT was, whether the person has experienced more than one DVT, the reasons the previous DVT occurred, its size, and so on,” explains Professor Whiteley.

“However, as a general rule, as long as the patient takes advice from a specialist, they should be able to fly again, even if it does mean taking medication or an injection to keep safe during the flight.”

Whiteley also notes that a one-off, small DVT suffered many years ago is unlikely to indicate a significant increased risk. However, if you have had “one or two major DVTs” with causes that have not been investigated and you’ve not been prescribed anticoagulation medication, you might be advised not to fly until you’ve seen a specialist. 

The British NHS guidelines for preventing future blood clot when flying is to wear flight socks or compression stockings, do plenty of exercises, walk around whenever you can, avoid alcohol and drink plenty of water.

How long after DVT can I fly?

While this varies hugely from person to person, if you are out of the recovery phase, taking anticoagulation medication (such as warfarin) and doing plenty of exercise, the risk of you developing DVT again is low and you should be able to fly as and when you want. This includes long-haul flights.

Your doctor will be able to tell you whether this will be a few weeks or a few months. 

Does the cause of my DVT affect the risk of suffering another episode?

Not always but it might do – and this is why having the cause investigated is important. “It was previously thought that having one case of DVT will put you at risk forever. However, it’s now recognised that DVTs come in different shapes and sizes, and for different reasons,” explains Whiteley. “This is why it’s really important to not only receive the correct treatment, but also find out what the underlying cause was, so that future problems can be avoided.” 

What else can I do to reduce my risk?

There are things you can do to lower the risk of DVT – and Professor Whiteley points out that these are things everybody can benefit from, not just those with a history or who are deemed ‘higher risk’.  

“I would recommend keeping well hydrated, both in the lead up to and during a flight, and making sure you move around in the cabin every half-hour or so,” he suggests. “If your flight is longer than four hours, or if you have any predisposing medical conditions [which may put you at increased risk of DVT], I would also suggest wearing properly fitted grade-two graduated compression stockings, at least to the knee if not above.”

If you are able to take aspirin, you might want to consider taking 75mg before flying, though Whiteley notes that “whether this actually helps is unknown”. 

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Flying after a pulmonary embolism

If your DVT developed into a pulmonary embolism, you will likely be taking anticoagulants following your treatment. It’s a good idea to seek the advice of your doctor if you’re planning on flying anytime soon, but the actions you can take to avoid future pulmonary embolisms are to continue to take any prescribed anticoagulant medication, wear compression stockings, exercise regularly and drink plenty of water.

The other question pulmonary embolism sufferers ask is “how long do I have to wait to fly after my pulmonary embolism?” The answer is there is no rule of thumb for this – you might be more or less at risk based on your age, weight, fitness or family medical history.

More information on this can be found on the NHS page.

Travel insurance for deep vein thrombosis, blood clots and pulmonary embolisms

If you've had a thrombosis in the past, it's worth mentioning this to your travel insurer to make sure that you’re covered just in case you develop another clot during your trip, which causes the need for medical treatment.

We’re here to help you compare quotes from a variety of specialist insurers.

Using our comparison tool, you will be able to declare your pre-existing medical conditions quickly and easily online and get the most competitive quotes based on your condition(s).

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