✔ Backed by: Centers for Disease Control and Prevention (CDC) · World Thrombosis Day. Each fact links to its source, and the full list is at the bottom of this post.
Call 911 right away if you or someone near you has sudden trouble breathing, chest pain that gets worse with a deep breath or cough, coughing up blood, a fast or uneven heartbeat, or feels faint. These can be signs of a blood clot in the lungs. CDC says to seek medical help immediately for these signs [1].
October 13 is World Thrombosis Day [2]. The day is led by the International Society on Thrombosis and Haemostasis. Its goal is to help people spot the warning signs of blood clots and learn how to prevent them [2]. “Thrombosis” simply means a clot that forms inside a blood vessel and can block blood flow [2].
Clots can happen to anyone. The good news is that a little knowledge goes a long way. When you know your risk and the warning signs, you can act fast and get care sooner. This post is for anyone who has been in the hospital, had surgery, cares for a loved one, or is planning a long trip. You do not need to memorize medical words. You just need to know what to watch for and who to call.
Two kinds of blood clot to know
Doctors often use the term VTE, which stands for venous thromboembolism. It covers two related problems [1]. The first is a DVT, or deep vein thrombosis. This is a clot in a deep vein, most often in the lower leg, thigh, or pelvis [1]. Signs usually show up in the arm or leg with the clot. They can include swelling, pain or tenderness, warmth, and redness or a change in skin color. CDC says to see your doctor as soon as possible if you notice these signs [1].
The second is a PE, or pulmonary embolism. This happens when part of a clot breaks off and travels to the lungs. It can be life-threatening [1]. That is why the warning signs at the top of this post matter so much. Trouble breathing, chest pain that gets worse with a deep breath, coughing up blood, a racing heartbeat, or feeling faint all need help right away.
Here is the tricky part. CDC notes that about half of people with a DVT have no symptoms at all [1]. So your body may not always send a clear signal. Clots can also leave lasting effects. CDC says one-third to one-half of people who have a DVT will have a long-term problem, such as ongoing swelling or pain in the leg [1]. Knowing your risk is just as important as knowing the signs.
What raises the risk
Clots often form when blood flow slows down, when a vein gets hurt, or when hormones change how blood clots. CDC lists many risk factors [3]. Here is a short version you can scan:
- A hospital stay, bed rest, a leg cast, or sitting for a long time
- Broken bones, a bad muscle injury, or major surgery, especially on the belly, pelvis, hip, or legs
- Cancer and its treatment, heart disease, lung disease, or inflammatory bowel disease
- Pregnancy and up to 3 months after giving birth, or medicines with estrogen, like some birth control or hormone therapy
- A past clot, an inherited clotting disorder, or a family history of clots
- Older age, overweight or obesity, or a catheter in a large vein
Having one item on this list does not mean you will get a clot. But CDC says the chance goes up even more when a person has more than one risk factor at the same time [3]. For example, imagine an older adult who has hip surgery and then spends most of the day in bed. Each of those things adds risk. That is just the kind of moment when a quick talk with the care team can help.
Blood clot risk in the weeks after the hospital
Many people think of the hospital as the risky place and home as the safe place. With clots, it is not that simple. Among surgery patients who got a clot, CDC reports that 40% happened during the hospital stay and 60% happened up to 90 days after leaving [4]. CDC also says more than a third of blood clots found each year are linked to a recent hospital stay, and most of those show up after the person goes home [4].
There is real hope in these numbers. CDC says as many as 70% of clots linked to health care can be prevented [4]. Yet CDC also reports that fewer than half of hospital patients get the recommended prevention steps, and most providers do not check clot risk again at discharge [4]. That gap is where your questions come in.
Before you or your loved one leaves the hospital, it is okay to speak up. You can say: “Before I go home, can we talk about my risk for a blood clot?” Here are a few more questions to bring:
- “Was my clot risk checked again before discharge?”
- “Is anything being done to help prevent a clot, like medicine or compression stockings?”
- “Which signs mean I should call you, and which mean I should call 911?”
CDC names blood thinners, also called anticoagulants, and compression stockings as ways to help prevent clots [4]. Whether either one is right for you depends on your own health, so that choice belongs with your care team. If you are given a blood thinner, follow your clinician’s directions and bring your questions to your pharmacist. Do not start, stop, or change it on your own.
Tell your care team your full story
Your care team can only plan around what they know. CDC encourages patients to talk about anything that may raise their clot risk [4]. That includes a past clot, an inherited clotting disorder, or a family member who has had a clot. It also includes hormone medicines, a pregnancy or birth in the last 3 months, cancer treatment, and being age 55 or older [4]. If you are not sure whether something matters, mention it anyway. You can say: “My mother had a blood clot after her knee surgery. Does that change anything for me?”
Caregivers and support people can help a lot here. A partner, adult child, or friend can keep the medicine list and family history handy. They can also ask the questions if the patient is tired, in pain, or just overwhelmed. Many people find it easier to remember the plan when two people heard it.
Tru-Tips: Ask your care team how much you should be up and moving once you are home. Then set a gentle phone reminder to get up and walk during the day. CDC suggests starting to move as soon as you can after being in bed from surgery, illness, or injury [1].
Keep moving on long trips
Long trips are another time to think about clots. CDC says anyone traveling more than 4 hours, by plane, car, bus, or train, can be at risk [5]. Most people who get a travel-related clot also have another risk factor. Examples include surgery or an injury in the last 3 months, a past clot, or active cancer [5].
The steps that help are simple. CDC suggests moving your legs often and walking around every 1 to 2 hours [5]. While you sit, stretch your legs out and pull your toes toward you [5]. Loose clothing can help too [1]. On a road trip, plan stops where everyone can get out and stretch. Some people may benefit from compression stockings, so ask your doctor if they are right for you [5]. If you have any of the risk factors above, it is wise to talk with your doctor before a long trip.
Let’s talk about it
Did anyone on your care team talk with you about blood clot risk before you left the hospital? What helps you or your family remember the warning signs? Share your tips in the comments so others can learn from you.
One Tru Step: Write the clot warning signs on a card, and keep it with your discharge papers or on your fridge, so you and your family know what to watch for and when to call 911.
Sources and further reading
- CDC: About Venous Thromboembolism (Blood Clots)
- World Thrombosis Day (October 13)
- CDC: Risk Factors for Blood Clots
- CDC: Understanding Your Risk for Healthcare-Associated Blood Clots
- CDC: Understanding Your Risk for Blood Clots with Travel
Sources checked October 15, 2026. General education; individual care and coverage questions require an appropriate professional.
Related Health Hubs
Join the conversation 💬
This is your space. Share a tip that helped you, ask the question you have been wondering about, or cheer on someone going through the same thing. Your comment shows up right away, and no account is needed.
Our house rules (they keep this a feel-good spot): Be kind. Stay on topic. Keep it free of religion, politics, and anything hurtful. Comments that break these rules are removed.
Protect your privacy: Use a first name or nickname, and skip full names, phone numbers, and personal health details.
If you or someone you know is in crisis, call or text 988. In an emergency, call 911.