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Deep Vein Thrombosis

Systemic Conditions Affecting the Feet· Also known as: DVT, blood clot in the leg, venous thrombosis of the legUpdated Nov 2026

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At a Glance

DVT is a clot that forms in one of the deep veins, most often in the leg. It affects about 1 in 1000 people. The main sign is pain and swelling in one leg, often in the calf or thigh. A clot can travel to the lungs, which can be life-threatening, so a DVT needs to be taken seriously. The main treatment is blood thinners, usually tablets taken for at least 3 months, and many people do well with them. The "When to see a podiatrist" section lists the signs to act on.

What is it?

Deep vein thrombosis (DVT) is a blood clot in one of the deep veins of your body. These are the larger veins that sit deep inside your muscles. Most often the clot forms in the leg, usually in the lower leg, thigh or pelvis. It can also form in an arm, especially where a large intravenous line (a thin tube into a vein) has been placed, or in the abdomen.

DVT occurs in about 1 in 1000 people. If a clot isn't treated, a piece can break away and travel to the lungs. This is called a pulmonary embolism, and it can be life-threatening.

A clot below the knee was once thought to be harmless. It isn't. These clots can grow upwards into the larger veins, come back, travel to the lungs, or cause long-term leg problems.

Who does it affect?

DVT becomes more common as people get older. Clots in the leg veins affect about 88 to 112 people in every 100,000 each year. When DVT and clots in the lungs are counted together, they are the third most common heart and blood vessel problem. More than an estimated 10 million people around the world are affected each year.

Some people have a higher chance of a clot. This includes people who:

have had surgery, especially on bones and joints, or who can't move around much
have cancer, or are having cancer treatment
are pregnant
have had a blood clot before
are overweight or smoke
have a blood clotting condition, including one passed down in families

These are links, not guarantees. A DVT can also happen with no obvious cause, so not having any of these doesn't rule it out.

Signs and symptoms

A DVT usually causes throbbing pain and swelling in one leg, most often in the calf or thigh. The leg may feel tender, and the skin over the clot may feel warm. The skin around the sore area can look red, blue or darker than usual. On brown or black skin, this change may be harder to see. A good clue is one leg that is more swollen, painful, warm or discoloured than the other. Both legs are rarely affected.

Symptoms can also appear in an arm if that is where the clot is. Occasionally the only symptom is pain low in the tummy, which can mean a rare clot in a pelvic vein. Some people have no symptoms at all. This is called a silent DVT.

The signs of DVT are not specific, and they can look like other conditions. A clot that reaches the lungs can cause sudden chest pain and shortness of breath. See the "When to see a podiatrist" section for what to do.

What causes it?

A DVT usually forms for one of three reasons. Blood may flow too slowly through the deep veins. The lining of a vein may be damaged. Or something may make your blood clot more easily than usual.

When a vein is damaged, a chemical in your blood called thrombin switches on. It forms long, sticky strands that clump together with tiny blood cells called platelets. Together they make a clot.

Everyday triggers include sitting still for a long time, such as on a flight of more than 4 hours, or being on bed rest in hospital or a nursing home. Not moving raises the chance of a clot, especially when other risk factors are present.

The chance of a clot is highest after major surgery or a major injury, and during infection and inflammation. After surgery, the risk is greatest in the first 3 months and then lowers with time.

How is it diagnosed?

The signs of a DVT aren't specific, so symptoms alone can't confirm or rule it out. A doctor works it out in steps. First they score how likely a clot is. Then you may have a D-dimer blood test and an ultrasound scan. The scan is what confirms a DVT.

A normal D-dimer result rules out a clot only when the chance was already low. When the chance is higher, the test alone can't rule it out.

Other problems can look like DVT, such as a skin infection (cellulitis). Rarely, a burst artery bulge behind the knee (ruptured popliteal artery aneurysm) is mistaken for one. So the cause should be confirmed before blood thinners are assumed.

Treatment

The main treatment for DVT is blood thinners (also called anticoagulants), with gentle activity alongside.

Looking after it at home

Stay gently active. Walking or swimming is recommended. While you are on blood thinners, avoid contact sports and other activities that may cause injury or bruising. Simple cuts and bruises can bleed more than usual on these medicines.

Treatment from your doctor

Blood thinners are the mainstay of treatment. They are usually tablets, such as rivaroxaban, taken for at least 3 months to lower the chance of another clot. Take the full course of blood-thinning medicine your doctor sets.

The newer tablets (such as rivaroxaban, apixaban, dabigatran and edoxaban) work about as well as the older blood thinner warfarin. They probably cause less major bleeding than warfarin.

Bleeding is still the main limit of these medicines. The risk is higher in older people and in people with other health conditions.

Other options

Clot-dissolving treatment is kept for life-threatening or limb-threatening cases, such as a massive clot in the lungs that makes circulation unstable. It is given alongside blood thinners. Specialist doctors make this decision, not you, and it carries a bleeding risk.

Recovery

Many people do well with treatment. But a DVT can come back, and it can leave lasting problems, so it helps to know what to expect.

Up to 25 to 30 per cent of people with a DVT or a lung clot have another clot. Untreated, around 5 to 15 per cent of people with a DVT may die from a clot in the lungs.

Some people develop post-thrombotic syndrome (long-term leg pain, swelling and heaviness, and in severe cases a leg ulcer). Estimates range from 25 to 40 per cent of people, and above 50 per cent in some groups. It can affect how well you move and your quality of life. A clot below the knee can lead to these problems too.

Finish your full course of blood thinners and go to your follow-up visits.

Preventing it

You can lower your chance of a clot, and a few simple habits help.

On long journeys, keep moving.

If you are having surgery, will be off your feet for a long time, or have several risk factors, ask your doctor about preventive treatment. Preventive treatment in high-risk situations significantly lowers the chance of a clot.

Outside these times, stay gently active day to day.

When to see a podiatrist

When to book

Talk to your healthcare provider about your risk of a blood clot and how to prevent one if you have had surgery, will be immobile for a long time, or have other risk factors.

When to get help sooner

Call your local emergency number if:

you suddenly become short of breath, have chest pain or cough up blood
you have bleeding that won't stop when you press firmly on it

Get urgent medical assessment (see your GP today, or go to an urgent care clinic or the nearest emergency department) if:

your calf or leg on one side becomes swollen and painful, especially if it is also warm or red

Frequently asked questions

What is the difference between a DVT and a clot in the lungs?

In a DVT, a clot forms in a deep vein, most often one in the leg. A clot in the lungs (pulmonary embolism) can happen if the clot travels there. Sudden breathlessness or chest pain can be a sign of this. See the "When to see a podiatrist" section.

Can I fly or take long car trips after a DVT?

If you have had surgery or have several risk factors, ask your healthcare provider about how to prevent clots. Sitting still for a long time raises the chance of a clot, so on journeys of 4 hours or more by plane, train or car, keep moving.

Can I tell a DVT from a muscle strain myself?

Not reliably. The two can feel alike, and symptoms alone can't confirm or rule out a clot. A new painful, swollen leg should be taken seriously, and the "When to see a podiatrist" section sets out the next step.

What if I'm not getting better on treatment?

Go back to the doctor who is treating you rather than waiting. Advanced treatments, such as clot-dissolving medicine, are decided by specialist doctors, so the right step is a medical review, not managing it yourself.