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Deep vein thrombosis (DVT) is a blood clot in a deep vein, usually in the calf or thigh. Typical symptoms are swelling, pain or cramp-like tenderness, warmth and redness in one leg. If part of the clot travels to the lungs it causes sudden breathlessness or chest pain, which is a medical emergency.
Deep vein thrombosis, or DVT, is a blood clot in one of the deep veins of the body, most often in the leg or pelvis. The classic deep vein thrombosis symptoms are swelling, pain and warmth in one leg. The bigger danger is that a piece of the clot can break off and travel to the lungs, causing a pulmonary embolism, which needs urgent treatment.
DVT often follows a spell of not moving much: an operation, a hospital stay, a long flight or weeks in bed. This guide covers the symptoms to watch for, who is at risk, how DVT is diagnosed and treated, and the signs that must not wait.
Key Takeaways
- The classic DVT signs are swelling, pain or tenderness, warmth and colour change in one leg, often starting in the calf. Some people have no symptoms at all.
- A swollen leg plus sudden breathlessness, chest pain or coughing up blood suggests a clot has reached the lungs. That is an emergency: call for help immediately.
- Recent surgery, immobility, long journeys, pregnancy, hormone medicines, cancer, obesity, smoking and a family history of clots all raise the risk.
- A Doppler ultrasound of the leg veins confirms or rules out DVT. You cannot do this by looking at the leg.
- Treatment is with prescribed blood thinners for at least 3 months. Never start, stop or adjust these on your own, and do not self-treat with aspirin.
What Is Deep Vein Thrombosis?
Your legs have two sets of veins: surface veins just under the skin, and deep veins inside the muscles that carry most of the blood back to the heart. A thrombosis is a clot; a DVT is a clot in one of those deep veins.
Clots form when blood flow slows, when a vein wall is injured, or when the blood clots more easily than usual. Often two or three happen together, which is why the risk jumps after surgery, during long spells of lying still, and in pregnancy.
DVT vs varicose veins
DVT is not the same as varicose veins, which are swollen, twisted surface veins with a different set of treatment options. Deep vein clots sit out of sight and are more dangerous.
Deep Vein Thrombosis Symptoms: What to Look For
DVT symptoms vary, and some people notice nothing until a complication occurs. When present, they usually affect one leg only:
- Swelling in one leg (or arm) that often appears quite suddenly
- Pain or tenderness that may feel like a cramp or a pulled muscle, often in the calf
- Skin that feels warm over the swollen area
- Redness or darker discolouration of the skin
- Surface veins that look more prominent than usual
Pain that worsens when you stand or walk, and a calf that feels tight or heavy, are typical. Swelling in both legs at once is more often due to heart, kidney or liver problems, but still needs a doctor.
Blood clot in leg or something else? Common look-alikes
| Possible cause of a swollen or painful leg | Typical pattern | What usually sets it apart |
|---|---|---|
| Deep vein thrombosis | One leg; swelling, ache or cramp, warmth, colour change; often after surgery, travel or immobility | Whole calf or leg swells; a risk factor is present; does not ease with rest |
| Muscle strain | Sudden pain during activity, tender at one spot | Little swelling early on; eases with rest over days |
| Cellulitis (skin infection) | Hot, red, spreading area, often with fever | Sharp red edge, feeling unwell; can mimic DVT, so a scan is often still needed |
| Varicose veins | Aching, heavy legs at the end of the day, visible twisted veins | Usually both legs; long-standing; no sudden swelling |
| Fluid retention (heart, kidney, liver) | Both legs, painless, dents when pressed | Symmetrical; other signs such as breathlessness or reduced urine |
This table is a guide, not a diagnosis. Only a Doppler ultrasound can rule DVT in or out; when in doubt, get scanned.
When a clot reaches the lungs
If part of the clot breaks off and travels to the lungs (a pulmonary embolism), the picture changes suddenly. The pulmonary embolism warning signs below are an emergency, not a wait-and-see.
Emergency: call for help immediately if you have
- Sudden shortness of breath
- Chest pain that is worse when you breathe in
- Coughing up blood
- A racing heartbeat, light-headedness or fainting, especially alongside a swollen or painful leg
Do not drive yourself. Call an ambulance or get to the nearest emergency department at once.
Unittas Hospital's emergency and critical care unit is open round the clock for suspected clots.
What Causes DVT, and Who Is Most at Risk?
If you are wondering what causes deep vein thrombosis, it is rarely one thing. Common risk factors include:
- Long periods of immobility: bed rest, long-haul flights, long car or train journeys
- Recent surgery, especially orthopaedic (hip or knee) or abdominal operations
- Injury to a vein, including fractures
- Pregnancy and the weeks after giving birth, one reason some pregnancies are managed as high-risk
- Hormone-based contraception or hormone replacement therapy
- Cancer and some cancer treatments
- Being overweight
- Smoking
- Older age
- A personal or family history of blood clots, or an inherited clotting disorder
DVT after surgery or a hospital stay
The weeks after an operation are the highest-risk period most people will face. Surgery injures tissue, the blood becomes stickier as part of healing, and you move far less than usual. That is why hospitals use blood-thinning injections, compression stockings and calf pumps, and why nurses get you walking early.
If you are planning surgery, ask what clot prevention you will receive. Once home, do not dismiss a new swollen or painful leg as just the operation. That is when a DVT is most likely.
How Is DVT Diagnosed?
The doctor will assess your symptoms and risk factors, and then usually arrange:
- A D-dimer test, a blood test that measures a substance released when clots break down. A normal result in a low-risk person makes DVT unlikely; a raised one needs a scan
- A colour Doppler ultrasound of the leg veins, the standard test to see the clot and how far it extends; painless and quick
- If a pulmonary embolism is suspected, imaging of the chest, usually a CT scan of the lung arteries
You cannot rule DVT in or out at home, and a doctor cannot by examination alone. If DVT is suspected, the venous Doppler scan should be done the same day, and treatment can start as soon as the result is back.
How Is DVT Treated?
The main treatment is anticoagulant medicine, commonly called blood thinners. These do not dissolve the clot on the spot; they stop it growing and prevent new clots while your body slowly breaks the existing one down. Treatment usually lasts at least 3 months, sometimes much longer, depending on the cause and your risk of another clot.
In severe cases, such as a very large clot or a serious pulmonary embolism, doctors may use clot-dissolving medicines or place a filter in a large vein to catch fragments. Compression stockings may be advised to reduce swelling.
Do not self-treat a suspected clot
Do not take aspirin, leftover blood thinners or 'blood-thinning' herbal remedies on your own, and do not stop or change a prescribed anticoagulant without asking your doctor. The main risk of these medicines is bleeding, so dose and duration need medical supervision. Report black stools, blood in the urine or unusual bruising promptly.
Possible longer-term effects
Some people develop post-thrombotic syndrome: lasting swelling, aching, heaviness or skin changes in the leg months or years later. Prompt treatment, staying active, compression when advised and finishing your prescribed course all reduce this risk.
How Can You Prevent DVT?
Simple steps lower the risk, especially during high-risk periods. Many people ask how to prevent DVT on long flights; the first two points cover travel, and the rest apply around surgery and day to day:
- On journeys over about 4 hours, move your legs regularly, flex your ankles and walk the aisle when you can
- Drink water and go easy on alcohol while travelling
- Follow instructions on clot-prevention injections or tablets around surgery, and start walking as soon as your team allows
- Keep a healthy weight and do not smoke
- Wear compression stockings if your doctor recommends them
- If you have had a DVT before, tell any doctor planning surgery, prescribing hormones or advising you in pregnancy
When Should You See a Doctor About a Swollen or Painful Leg?
Do not wait to see if it settles. Here is a simple guide:
- New swelling, pain or warmth in one leg, especially after surgery, travel, illness or in pregnancy: get assessed the same day. A physician can examine you and arrange the scan.
- Any of those with breathlessness, chest pain, coughing up blood or fainting: emergency now. Call an ambulance.
- A known DVT on treatment with new bleeding, a worsening leg or new chest symptoms: contact your doctor or the emergency department the same day.
The action is the same in every case: pick up the phone or come in today. DVT is very treatable when caught early. Unittas Hospital's emergency department is open 24 hours.
DVT is serious, but it is also very treatable when it is recognised promptly. Know the pattern, one swollen, painful, warm leg, take it seriously after surgery or travel, and treat sudden breathlessness as the emergency it is. If something feels wrong, get it checked by a physician today.
Frequently Asked Questions
Can you get a DVT in both legs at the same time?
It is possible but uncommon. Most DVTs affect one leg. Swelling in both legs more often has another cause, such as heart, kidney or liver problems, but it still needs checking.
How long does a journey need to be to raise DVT risk?
Risk rises with journeys longer than about 4 hours, particularly if you sit still, are dehydrated or already have other risk factors.
Is a DVT the same as a varicose vein?
No. Varicose veins are swollen surface veins. A DVT is a clot in the deep veins, and it is more serious because part of it can travel to the lungs.
Can young, fit people get DVT?
Yes. Age raises the risk, but younger people can develop clots, especially with travel, hormone medicines, pregnancy, injury or an inherited clotting tendency.
Do blood thinners dissolve the clot immediately?
No. They stop the clot growing and prevent new ones. Your body breaks the existing clot down gradually over weeks to months.
How long will I need to take anticoagulants?
Usually at least 3 months. The exact duration depends on what caused the clot and your risk of another; some people need long-term treatment.
Can I fly after having a DVT?
Often yes, once treatment is established and your doctor agrees, usually with precautions such as compression stockings, regular movement and staying hydrated.
What is the difference between DVT and a pulmonary embolism?
A DVT is a clot in a deep vein, usually in the leg. A pulmonary embolism happens when part of that clot breaks off and lodges in the lungs. It is the life-threatening complication of DVT.
Should I stop hormonal contraception after a DVT?
Combined hormonal contraceptives increase clotting risk and are usually stopped after a DVT. Do not stop or switch on your own; ask your doctor about safer alternatives.
Is swelling after a DVT permanent?
Some swelling can persist, especially if post-thrombotic syndrome develops. Compression, elevation, staying active and completing treatment help reduce it.
One leg swollen, warm or painful?
Get it assessed today. A physician can examine you and arrange a Doppler scan the same day.
Do not sit on a swollen leg
DVT is simple to treat when it is caught early and dangerous when it is not. Call Unittas Hospital or come straight to our 24-hour emergency department.