While flying is a great way to get from place to place, sitting for several hours in a small area can raise the likelihood of developing blood clots in some individuals. This is especially crucial for long-distance travel, where passengers are sitting for long periods of time and have limited leg room.
A DVT flight risk is associated mainly with prolonged immobility, which can slow blood circulation in the legs and contribute to clot formation. Although most travellers do not develop blood clots after flying, people with certain medical conditions or existing risk factors may be more vulnerable.
Knowing the link between deep vein thrombosis flying and sitting for long periods can help you take the necessary precautions before, during and after your flight.
Whether you’re traveling for a short distance or heading overseas, understanding how to avoid DVT on a plane can help you make informed decisions about your health.
For those planning a long haul flight, check out our long haul flight health tips for more information on how to stay comfortable and healthy during a long haul flight.
What Is Deep Vein Thrombosis (DVT)?
Deep vein thrombosis (DVT) is a medical condition that occurs when a blood clot forms in a deep vein, usually in the lower leg or thigh.
Blood normally circulates continuously throughout the body. But if the blood flow slows down, a vein becomes damaged or the blood is more prone to clotting, a blood clot can form.
DVT is especially dangerous because a portion of the clot may detach and migrate to the lungs. This can cause a pulmonary embolism (PE), a potentially life-threatening condition that requires emergency medical treatment.
Anyone can get DVT, but there are some factors that make it more likely. One known risk factor is sitting for long periods of time during air travel, particularly if you have a medical condition or limited mobility.
Read the NHS guide to deep vein thrombosis for more information.
Can Flying Increase the Risk of DVT?
Yes. Air travel can make you more susceptible to DVT, especially if you are traveling for four hours or more.
The primary issue is lack of movement. Passengers who sit for long periods of time have less leg muscle activity, which can reduce blood flow in the deep veins.
This is more likely to happen on long-haul flights where there may be less opportunity to stand, stretch or walk around the cabin.
But, DVT does not always occur when a person flies. The overall risk is generally low for healthy travellers without additional risk factors. The risk is higher if sitting for long periods is coupled with other risk factors, including a history of blood clots, recent surgery, pregnancy or certain medical conditions.
Four hours is a threshold that is used in travel-related research, not a time when DVT suddenly starts.
The UK Civil Aviation Authority’s guidance on air travel and health states that sitting for more than four hours on an aeroplane or other mode of transport can raise the risk of blood clots forming.
What Are the Main DVT Risk Factors During Long-Haul Flights?
Knowing what factors increase the risk of DVT during long-haul travel can help you determine if you need extra precautions.
Although prolonged sitting is a common contributing factor, individual health conditions, physical characteristics and medical history also play an important role.
1. Long Flight Duration
The longer you remain seated without moving, the more likely blood circulation in your legs is to slow down.
Travels of four hours or more are typically linked to a higher risk of travel-related blood clots. Several long trips in a short time can also lead to extended periods of inactivity.
If you are travelling by connecting flights, take into account the total time spent sitting, including waiting times when you are not moving. Two connecting flights should not be assumed to be equivalent to one flight, as the risk of each flight depends on the length of the period of immobility and individual health factors.
2. Previous History of DVT or Blood Clots
Those who have had a previous DVT or pulmonary embolism may be at increased risk for another clot.
If you have a history of blood clots, consult your health care provider before travelling. They can evaluate your personal risk and suggest preventive measures.
3. Older Age
DVT is more likely to occur as people get older. Other factors may also be at play for older travellers, such as decreased mobility, chronic health conditions or previous medical procedures.
4. Recent Surgery or Injury
Recent surgery, especially of the hips, knees or legs, can make it more likely for blood clots to form.
Movement-restricting injuries can also be a risk factor. Travellers recovering from surgery should seek medical advice about when it is appropriate to fly.
5. Pregnancy and Recent Childbirth
Pregnancy naturally increases the body’s tendency to form blood clots. The risk remains elevated after childbirth, particularly during the first six weeks, although it can remain increased for longer.
Pregnant women and women who have recently given birth should consult a health care provider before travelling.
6. Obesity
Overweight or obesity can also be a risk factor for DVT, particularly if you are sitting for long periods of time on a long-haul flight.
7. Hormonal Medications
Certain hormonal drugs, such as oestrogen-containing contraceptives and hormone replacement therapy, can raise the risk of blood clots.
Individuals who are on these medications and have other risk factors for DVT should talk to their doctor about appropriate precautions.
8. Inherited or Acquired Clotting Disorders
Some health problems increase the risk of blood clots. These include inherited thrombophilia and some acquired clotting disorders.
People with known clotting disorders should obtain medical advice before undertaking long-distance air travel.
9. Height and Restricted Legroom
Body size can also play a role in the risk of blood clots during air travel.
Very short travellers (those shorter than about 160 cm) and very tall travellers (those taller than about 190 cm) are considered to be at potentially higher risk, according to the CDC Yellow Book.
If the feet do not reach the floor comfortably, shorter passengers may feel pressure behind their thighs, and taller passengers may find that they have limited legroom, making it difficult to move around.
Selecting a seat with enough legroom and moving around frequently can help minimize prolonged pressure and immobility.
10. Recent Illness and Serious Medical Conditions
Some diseases and health problems can make it more likely to form blood clots.
These include:
- Active cancer or recent chemotherapy.
- Heart failure.
- Inflammatory bowel disease, particularly during active inflammation.
- Serious respiratory illnesses.
- Recent hospitalisation or prolonged bed rest.
- Other conditions associated with inflammation or reduced mobility.
Those who have had a severe illness, such as COVID-19 or influenza, should assess their own health and mobility before embarking on a long trip.
If you have recently been seriously ill or hospitalised, consult your doctor before flying.
External medical guidance: The CDC’s travel-related blood clot guidance explains individual risk factors and ways to reduce the risk of blood clots during long journeys. The CDC Yellow Book: Deep Vein Thrombosis and Pulmonary Embolism also discusses the relationship between physical stature, restricted seating and travel-related clotting risk.
How to Prevent DVT on a Plane
Taking sensible precautions before and during your journey can help reduce the risk of developing blood clots.
These measures are especially important for passengers with existing risk factors.
1. Move Around During the Flight
Avoid remaining seated throughout the entire journey.
When it is safe to do so, stand up and walk around the aircraft cabin every one to two hours. Moving your legs helps activate the calf muscles, which support blood circulation.
If you cannot walk around regularly, change your sitting position and perform simple leg movements.
2. Perform Simple Leg Exercises
If you cannot leave your seat, perform simple exercises to keep your lower legs moving.
Try the following movements:
- Ankle circles: Rotate each ankle in both directions.
- Heel raises: Keep your toes on the floor and lift your heels.
- Toe raises: Keep your heels on the floor and lift your toes.
- Calf contractions: Tighten and relax your calf muscles repeatedly.
- Leg extensions: Straighten one leg at a time, where space allows.
These exercises help maintain movement in your lower legs while seated.
The CDC’s blood clot prevention advice for travellers recommends moving your legs frequently and walking around every one to two hours during long journeys.
3. Consider Graduated Compression Stockings
Graduated compression stockings apply gentle pressure to the legs, helping support blood circulation and reduce blood pooling.
Medical evidence suggests that properly fitted graduated compression stockings can reduce asymptomatic DVT in selected long-distance travellers.
The American College of Chest Physicians (ACCP) recommends that travellers at increased risk consider properly fitted, below-knee graduated compression stockings providing approximately 15–30 mmHg pressure at the ankle.
However, these stockings are not necessary for every passenger. Their suitability depends on individual risk factors.
Important fitting advice:
- Choose the correct size according to your leg measurements.
- Make sure the stockings fit smoothly without folds or bunching.
- Avoid stockings that are excessively tight or cause discomfort.
- Do not roll down the top of the stockings.
- Ask a healthcare professional for advice if you have circulation problems or existing leg conditions.
Poorly fitted compression garments can cause discomfort or pressure-related problems. Seek professional advice about the correct type and fit.
For further information, see the ACCP clinical guidelines on preventing venous thromboembolism.
4. Wear Comfortable, Loose-Fitting Clothing
Tight clothing around the waist, thighs or legs may make movement uncomfortable during a long journey.
Choose loose-fitting clothing that allows you to change positions and move your legs easily.
Avoid placing heavy bags under the seat in front of you if they restrict your leg movement.
5. Stay Normally Hydrated
Drink water regularly throughout your journey and avoid becoming dehydrated.
Although maintaining hydration is sensible for general health, drinking extra water alone has not been proven to prevent travel-related DVT.
Regular movement and appropriate medical precautions remain important.
6. Choose an Aisle Seat
An aisle seat may offer greater freedom to get up, stretch and walk around for a long haul flight.
If you have a concern with DVT, select a seat that will make it easier to move your legs during the ride.
7. Avoid Excessive Alcohol and Unnecessary Sedatives
Unnecessarily taking large amounts of alcohol or sedatives and sleeping pills could decrease your activity on a long flight.
Certain sleep medications will make passengers very immobile, especially when they are seated in a confined area.
Don’t consume too much alcohol and be sure to talk to a healthcare provider before taking a sleeping pill to help you sleep through an extended flight.
If you are taking medication, please take it according to your doctors’ advice.
8. Speak to Your Doctor Before Flying
Please consult a doctor before travelling if you have had DVT in the past, if you are recently operated or have a clotting disorder or have a number of risk factors.
Prescription anticoagulant medication is recommended for some high-risk travellers.
However, blood-thinners are never used on their own for the prevention of DVT while travelling.
Aspirin is not routinely recommended to prevent travel-related DVT. All three organisations, the ACCP, CDC and UK Civil Aviation Authority, discourage the routine use of aspirin for this purpose.
Read the NHS guidance about preventing DVT for more information.
What Are the Symptoms of Blood Clots After Flying?
It is important to be aware of the signs and symptoms of blood clots after flying because DVT can occur while you are flying or upon arrival at your destination.
Several hours or days after flight may be sufficient for the onset of symptoms. The risk of blood clots from travel is highest in the first one to two weeks after the trip, but may be present for up to eight weeks after the trip.
Common signs of DVT include:
- One leg swelling especially around the calf or ankle.
- Pain or tenderness in the leg.
- Warmth in the affected area.
- Redness or discolouration of the skin.
- Unexplained discomfort or heaviness in one leg.
These symptoms do not necessarily mean that you have DVT. They should be evaluated quickly by a health care professional, however.
DVT Swelling vs Normal Post-Flight Leg Swelling
Some people may have swelling in the feet and ankles for a short period of time after sitting for several hours. This may happen because of fluid build up in the legs during extended sitting time.
There are some distinctions that must be comprehended:
| Possible DVT symptoms | Common post-flight swelling |
|---|---|
| Often affects one leg | Often affects both feet or ankles |
| May include pain or tenderness | May be painless |
| Can involve warmth or skin discolouration | Usually improves with movement and elevation |
| Requires prompt medical assessment | Often settles after walking or resting |
These differences are not the best method to diagnose or rule out DVT. Not all people will have symptoms of DVT and swelling may occur in different ways.
Swelling, pain, warmth and redness, especially in one leg, should not be ignored as being due to normal travel swelling, and should be assessed by your GP as soon as possible.
Warning Signs of Pulmonary Embolism
A pulmonary embolism can occur if a piece of a blood clot dislodges and moves into the lungs.
Symptoms may include:
- Sudden shortness of breath.
- Chest pain, particularly when breathing deeply or coughing.
- Coughing up blood.
- A rapid or irregular heartbeat.
- Fainting or severe dizziness.
A pulmonary embolism is an emergency situation. If you experience these symptoms, get medical help right away.
For further information, see the NHS guide to pulmonary embolism.
Who Should Take Extra Precautions When Flying?
While anyone can get DVT, some travellers should be extra diligent in protecting themselves against it.
You may need additional precautions if you:
- Have previously experienced DVT or pulmonary embolism.
- Have recently undergone surgery or experienced a significant injury.
- Are pregnant or have recently given birth.
- Have an inherited or acquired clotting disorder.
- Have active cancer or are receiving cancer treatment.
- Have limited mobility.
- Have serious medical conditions, including heart failure or active inflammatory bowel disease.
- Have several risk factors, such as older age combined with obesity or hormonal medication use.
If one or more of these circumstances apply to you, speak with your doctor before taking a long-haul flight.
Your healthcare professional can assess your individual risk and recommend appropriate preventive measures.
When Is It Safe to Fly After Having DVT?
Please be aware that if you have received a recent diagnosis for DVT, you should not presume that you are safe to travel by air because your symptoms have resolved.
Traveling is dependent on a number of factors, including:
- The location and severity of the clot.
- Whether you have experienced pulmonary embolism.
- Whether you have started anticoagulant treatment.
- Whether your condition is medically stable.
- Your overall health and any additional risk factors.
The NHS recommends that DVT patients should avoid taking flights or long journeys for at least two weeks following their first dose of blood-thinning treatment.
The British Thoracic Society (BTS) guidelines in the CDC Yellow Book also recommend a 14-day waiting period post-DVT or pulmonary embolism diagnosis before air travel.
Such is a general recommendation, though, and not automatic medical clearance. Before you travel, you should seek advice from your treating doctor.
Do not abandon or alter a prescription for an anticoagulant drug for a flight.
Read the NHS guidance on DVT recovery for further information.
Frequently Asked Questions About DVT and Flying
1. How long does a flight need to be to increase DVT risk?
Flights lasting four hours or longer are generally associated with an increased risk of travel-related blood clots. However, individual risk also depends on personal health, medical history and mobility during the journey.
2. Can you get blood clots after flying?
Yes. Blood clots can develop during or after air travel. Symptoms may appear hours, days or even weeks after a journey, so it is important to recognise warning signs after reaching your destination.
3. Do compression socks prevent DVT on flights?
Graduated compression stockings can reduce the risk of asymptomatic DVT in selected long-distance travellers. They may be particularly useful for people with additional risk factors, but their suitability and correct fit should be discussed with a healthcare professional.
4. Does drinking water prevent DVT when flying?
Staying hydrated is sensible, but drinking water alone has not been proven to prevent travel-related DVT. Regular movement and appropriate medical precautions are more important.
5. Should I take aspirin before a long-haul flight?
Aspirin is not routinely recommended for preventing travel-related DVT. If you have an increased risk of blood clots, speak with your doctor about appropriate preventive options.
6. Can healthy people develop DVT after flying?
Yes. Although the overall risk is low for healthy travellers, prolonged immobility during long-distance travel can increase the risk of blood clots. Regular movement is a sensible precaution.
7. How long after flying should I watch for DVT symptoms?
Remain alert to symptoms during your journey and for several weeks afterwards. Most travel-associated blood clots occur within the first one to two weeks, but the increased risk can persist for up to eight weeks.
8. Can taking sleeping tablets during a flight increase DVT risk?
Sleeping tablets may cause prolonged immobility, particularly if they make you sleep deeply without changing position. Avoid unnecessary sedatives during long journeys and discuss prescribed medication with your healthcare professional.
Final Thoughts
Understanding the connection between DVT flight risks and prolonged sitting is important when planning a long-distance journey. Although the overall risk of developing a blood clot during air travel is relatively low for most people, certain travellers may be more vulnerable because of their medical history or other risk factors.
Simple precautions, including moving every one to two hours, performing seated leg exercises, avoiding excessive alcohol and considering graduated compression stockings when appropriate, can help reduce the risk.
At World Flight Vibes, we believe that a safe and comfortable journey starts with being informed and prepared. Whether you are planning a short trip or an international long-haul flight, understanding how to prevent DVT on a plane can help you make smarter travel decisions.
If you have a history of blood clots or other significant risk factors, consult a healthcare professional before flying. Recognising the symptoms of DVT and seeking prompt medical attention can also help prevent serious complications.
With the right precautions, medical guidance and travel preparation, you can enjoy a healthier, safer and more comfortable journey with World Flight Vibes.
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