Heart and circulation

Can You Fly With a Blood Clot in Your Leg? What Sources Say and What to Ask

Can you fly with a blood clot in your leg? Guidance on timing differs. See the urgent signs first and clearance questions to ask the clinician treating it.

By Cardio Guardian Editorial TeamPublished October 15, 20269 min read

You may be able to fly with a blood clot in your leg once the clinician treating it agrees, but there is no single waiting time that fits everyone. Published guidance differs: the airline medical manual summarized in the CDC Yellow Book says travelers with a recent clot in a leg vein may fly once they have no symptoms and are stable on blood-thinning medicine, a UK clinical statement says air travel should be delayed for 2 weeks after diagnosis, and a US patient guide says it may be best to avoid flying in the first 4 weeks but that this is not an absolute recommendation. [1] [2] [3] The UK statement adds that there are no concrete data to support a safe time interval. [2] If you have leg signs that have not been checked yet, CDC says to contact your doctor as soon as possible. [4] Do not wait until after the trip.

Urgent symptoms come first. Call 911 for severe chest pain or pressure, severe shortness of breath, suddenly not being able to speak, see, walk or move, or suddenly being weak or drooping on one side of the body. [5] Difficulty breathing, a faster than normal or irregular heartbeat, chest pain or discomfort that gets worse with a deep breath or coughing, coughing up blood, or lightheadedness or fainting can be signs of a blood clot in the lungs (pulmonary embolism); CDC says to seek medical help immediately. [4] Do not wait for a routine callback from your provider: go to an emergency department or call 911 or your local emergency number for help. [5] New or worsening swelling of a leg, pain or tenderness you cannot explain, skin that is warm to the touch, or redness or discoloration of the skin can be signs of a blood clot in a deep vein (deep vein thrombosis); CDC says to contact your doctor as soon as possible. [4] [6] These steps apply before, during and after a trip; if signs start while you are away, use the local emergency number where you are. [5] If you take a blood thinner, do not stop, skip or change it for a trip on your own; CDC says to follow your doctor’s recommendations on medication use. [4]

Save questions for my appointment

This page is general education for adults. It cannot tell you whether or when you can fly, and it does not recommend any medicine, dose, compression product or home test.

Why a clot in the leg affects travel plans

A deep vein thrombosis is a blood clot in a deep vein, usually in the lower leg, thigh or pelvis; a pulmonary embolism happens when a clot breaks loose and travels through the bloodstream to the lungs. [7] A US patient guide for people newly diagnosed with either says the highest risk period for serious complications is in the first few days, when a clot can break off and travel to the lungs. [3] Lack of movement while traveling long distances can also raise the likelihood of blood clotting. [7]

CDC says anyone traveling more than 4 hours, whether by air, car, bus or train, can be at risk, and that the risk is generally very small even on a long trip; it depends on how long you travel and whether you have other risks, and a previous blood clot is one of them. [4] The CDC Yellow Book, written for clinicians, says most travel-associated clots happen in people who already have a risk factor and most occur within the first 1 to 2 weeks after the flight. [1] Age matters too: NHLBI says a clot in a vein can occur at any age, but the chance nearly doubles every 10 years after age 40. [8]

What published guidance says about timing

The sources below are the ones that address flying after a clot. Each was written for a different audience, and none sets a waiting time that fits everyone.

Published guidance on air travel after a clot in the leg: who it was written for, what it says and its limits
Source	Written for	What it says about timing	Limits
IATA Medical Manual, 2020 edition, as summarized in the CDC Yellow Book	Airlines worldwide; summarized for US clinicians advising travelers	Travelers with a recent clot in a leg vein may fly once they have no symptoms and are stable on blood-thinning medicine; the time frame can change after a medical assessment. [1]	An airline industry manual read through CDC’s summary, not a clinical study. [1]
British Thoracic Society Clinical Statement, 2022	UK clinicians caring for passengers with lung and breathing conditions	Air travel should be delayed for 2 weeks after a diagnosis of deep vein thrombosis or pulmonary embolism, and anyone with a clot in the last 6 weeks should be reassessed before air travel. [2]	Expert consensus; the statement says there are no concrete data to support a safe time interval, and UK practice may differ from US practice. [2]
Vascular Medicine patient information page, 2023	US patients newly diagnosed with deep vein thrombosis or pulmonary embolism	There is no clear guidance on the safety of plane travel right after a clot; it may be best to avoid flying in the first 4 weeks, but this is not an absolute recommendation, and the risks and benefits should be discussed with your doctor. [3]	A patient guide by three US clinicians, not a formal guideline. [3]
Aerospace Medical Association, Fitness to Fly and Medical Clearances, 2014	Physicians advising passengers	No waiting time; an individual with an unstable medical condition should not fly, and deep venous thrombosis is among the conditions a pre-flight medical evaluation should address. [9]	General aviation-medicine guidance from 2014, not specific to leg clots. [9]

The British Thoracic Society statement also says the risk-benefit balance needs to be assessed if more urgent air travel is needed, and that the chance of another clot while taking anticoagulation is extremely low. [2] Which timing, if any, applies to you depends on your clot, your treatment and your trip, so the decision belongs to the clinician who is treating you.

Why the clinician treating your clot makes the call

Treatment differs from person to person. NHLBI says not everyone diagnosed with a clot in a vein needs treatment, and that blood thinners may be taken for several months or for a lifetime, depending on factors such as the type of blood thinner and the cause of the clot. [10] The Vascular Medicine guide says the next steps after diagnosis vary with medical history, age and the circumstances of the clot, and that the location of the clot helps decide how long treatment lasts. [3]
Fitness to fly is a medical review. The Aerospace Medical Association says physicians should review the passenger’s condition, giving special consideration to the dosage and timing of any medicines, and that as a general rule an individual with an unstable medical condition should not fly. [9]
Airlines may ask for paperwork. The same guidance says some airlines require a medical certificate from the health care provider stating that the passenger is currently stable and fit for air travel, and that the physician should first check the airline’s website for its procedure. [9]
Prevention steps for the trip are individual. The CDC Yellow Book says decisions about preventive blood-thinning medicine for long-distance travelers at high risk should be made on an individual basis. [1] An American Society of Hematology guideline panel counts a prior blood clot among the things that put a traveler at substantially increased risk; its travel suggestions are conditional and based on very low certainty evidence. [11]
Medicines stay as prescribed. MedlinePlus discharge instructions for people treated for deep vein thrombosis say to take a prescribed blood thinner just the way your provider prescribed and to know what to do if you miss a dose. [6] Ask before changing anything for a trip.

What the sources tell travelers about the journey

These are general instructions from the sources; ask the clinician treating your clot which apply to you.

MedlinePlus discharge instructions for deep vein thrombosis say to get up and walk around often on a plane, bus or train, to stop often on car trips and walk around for a few minutes, and while sitting to wiggle your toes, tighten and relax your calf muscles and shift your position often. [6]
NHLBI’s travel tips include standing up and walking around every 1 to 2 hours if possible, wearing loose-fitting clothing and avoiding alcohol. [12]
The CDC Yellow Book says there is no evidence linking dehydration with travel-associated clots; staying hydrated is reasonable but cannot be recommended specifically to prevent them. [1]
Keep watching after you land: most travel-associated clots occur within the first 1 to 2 weeks after the flight, and the signs in the urgent box above still apply. [1]
The same MedlinePlus instructions say to read food labels to check the amount of salt (sodium) in foods and to ask your provider how much sodium is OK for you each day. [6] To practice finding sodium on a label, try the food label reading worksheet.

Clearance questions to save for your appointment

Write your answers before your visit and take them to the clinician treating your clot. The questions follow what the sources say matters before air travel after a clot: how recent and stable it is, your treatment, your trip and what to watch for. [2] [9] [1] This page does not collect anything you write.

Download the clearance question sheet (PDF, 2 pages, 47 KB)

About my clot and treatment

When was my clot diagnosed, and which vein was it in?
Was the clot only in my leg, or was there also a clot in my lungs?
Do I still have swelling, pain or other symptoms in that leg, and are they getting better or worse?
Which blood thinner am I taking, when did I start it, and how long am I expected to take it?
Have I missed any doses, or has my medicine changed recently?
Have I had a blood clot before, or does anyone in my family have a history of clots or a clotting disorder?

About the trip

When do I plan to travel, and how long is each flight or leg of the journey?
Will part of the trip be a long car, bus or train ride?
Will I be able to get up and move around during the journey?
Is the trip urgent, or could the date move if needed?
Where am I going, and how would I get medical care there?
Does my airline ask for a medical certificate or form?

Other things that can raise my clot risk

Have I recently had surgery, an injury or a hospital stay?
Am I pregnant, or have I given birth in the last 3 months?
Do I use estrogen-containing birth control or hormone replacement therapy?
Do I have active cancer or recent cancer treatment, a heart or lung condition, or diabetes?

Questions to ask the clinician treating my clot

Is my condition stable enough for this trip, and when would you be comfortable with me flying?
Do I need a check-up or any test before I go?
Should I take any extra steps for this trip, such as compression stockings or other prevention, or none?
How should I take my blood thinner on travel days and across time zones, and what should I do if I miss a dose?
Can you complete a medical certificate for the airline if it asks for one?
Which signs during or after the trip mean I should get emergency care, and which mean I should call you?

Bring to your appointment

This sheet with your answers
A list of every medicine and supplement you take, with the times you take them
Your travel dates, flight lengths and destination
Any airline medical form or certificate you have been asked to complete
Reports from your clot diagnosis, such as ultrasound results, if you have them

What this page cannot tell you

It cannot tell you whether or when you can fly. Only the clinician treating your clot, who knows your history, tests and treatment, can make that call. [9]
It does not recommend any medicine, dose, compression product or test, and nothing here is a reason to start, stop or change a medicine on your own. [6]
The timing guidance comes from an airline industry manual, a UK statement for passengers with lung conditions and a US patient guide. The UK statement says there are no concrete data supporting a safe interval, and the travel-risk findings describe travelers in general, not people with a current clot. [1] [2] [3]
The American Society of Hematology guideline dates from 2018 and the Aerospace Medical Association guidance from 2014; newer evidence may change them. [11] [9]

For more on how blood moves through the body, browse Heart and circulation or test what you know with our circulatory system worksheets.

Common questions

How long after a blood clot in my leg can I fly?

Published guidance differs, from once you have no symptoms and stable treatment in the airline manual summarized by CDC, to 2 weeks after diagnosis in the British Thoracic Society statement, to possibly avoiding the first 4 weeks in a US patient guide that says this is not absolute. [1] [2] [3] The clinician treating your clot decides which applies to you.

Can I fly while taking a blood thinner?

The sources describe people flying while on blood thinners: the airline manual summarized by CDC refers to travelers who are stable on blood-thinning medicine, and the British Thoracic Society says the chance of another clot while taking anticoagulation is extremely low. [1] [2] CDC says to follow your doctor’s recommendations on medication use, so ask how to take your doses on travel days. [4]

Can flying cause a blood clot in the leg?

Long trips can raise the chance of a clot, mainly because of sitting still for a long time. NHLBI says flights of more than 4 hours more than double the likelihood, while the CDC Yellow Book says studies suggest 2 to 4 times the risk but the data are inconsistent. [12] [1] MedlinePlus says the added risk from sitting while traveling is most likely when you also have one or more other risk factors. [13]

Will my airline need a note from my doctor?

It may. The Aerospace Medical Association says some airlines require a medical certificate stating that the passenger is currently stable and fit for air travel, and that physicians should check the airline’s website for its medical clearance procedure. [9]

Should I wear compression stockings on the flight?

Ask the clinician treating your clot; the sources do not give one answer for everyone. NHLBI’s travel tips include compression stockings, MedlinePlus says to wear pressure stockings if your provider prescribed them, and CDC says some people at risk may benefit. [12] [6] [4] The CDC Yellow Book summarizes guidance that does not recommend them for long-distance travelers who are not at increased risk, while the American Society of Hematology suggests them, or another option, for people at substantially increased risk, based on very low certainty evidence. [1] [11]

What if symptoms start during or after the flight?

Follow the urgent box below wherever you are: possible signs of a clot in the lungs need emergency help through 911 or the local emergency number, and new or worsening leg signs need a call to your doctor as soon as possible. [5] [4] The CDC Yellow Book says most travel-associated clots occur within the first 1 to 2 weeks after the flight. [1]

Is a long car or train trip any different?

CDC says anyone traveling more than 4 hours by air, car, bus or train can be at risk, and the CDC Yellow Book says a similar increase in risk is seen with other kinds of long-distance travel. [4] [1] MedlinePlus discharge instructions say to stop often on car trips and get out and walk around for a few minutes. [6]

Urgent symptoms come first. Call 911 for severe chest pain or pressure, severe shortness of breath, suddenly not being able to speak, see, walk or move, or suddenly being weak or drooping on one side of the body. [5] Difficulty breathing, a faster than normal or irregular heartbeat, chest pain or discomfort that gets worse with a deep breath or coughing, coughing up blood, or lightheadedness or fainting can be signs of a blood clot in the lungs (pulmonary embolism); CDC says to seek medical help immediately. [4] Do not wait for a routine callback from your provider: go to an emergency department or call 911 or your local emergency number for help. [5] New or worsening swelling of a leg, pain or tenderness you cannot explain, skin that is warm to the touch, or redness or discoloration of the skin can be signs of a blood clot in a deep vein (deep vein thrombosis); CDC says to contact your doctor as soon as possible. [4] [6] These steps apply before, during and after a trip; if signs start while you are away, use the local emergency number where you are. [5] If you take a blood thinner, do not stop, skip or change it for a trip on your own; CDC says to follow your doctor’s recommendations on medication use. [4]