Deep Vein Thrombosis (DVT)

What is a DVT?

A deep vein thrombosis (DVT) is a blood clot that forms within one of the deep veins of the body.

It most commonly develops in the leg, usually in the calf or thigh, although a DVT can occasionally occur elsewhere, such as the arm or pelvis.

A DVT needs prompt medical assessment because part of the clot can sometimes travel through the circulation to the lungs. This is called a pulmonary embolism (PE) and can be life-threatening.

What are the symptoms of a DVT?

Symptoms commonly affect one leg rather than both and may include:

  • Throbbing, aching or cramping pain, usually in the calf or thigh

  • New or unexplained swelling of one leg

  • Warmth around the painful area

  • Red, blue or darker skin around the affected area

  • More prominent or swollen veins

  • Tenderness or a feeling of heaviness in the leg

Changes in skin colour can be harder to see on brown or black skin, so new swelling, warmth and tenderness are particularly important signs.

Not everybody with a DVT has every symptom, and some DVTs cause relatively few symptoms.

Who is more at risk?

A DVT can happen to anyone, and occasionally there is no obvious reason.

The likelihood is increased by factors including:

  • Previous DVT or pulmonary embolism

  • A family history of blood clots

  • Increasing age

  • Smoking

  • Obesity

  • Cancer

  • Heart failure

  • Varicose veins

  • Thrombophilia – a condition which makes the blood more likely to clot

  • Some inflammatory conditions

  • Pregnancy and the first 6 weeks after having a baby

  • HRT

  • The combined contraceptive pill or other contraception containing oestrogen

  • Recent surgery

  • A recent hospital stay

  • Being confined to bed or significantly less mobile

  • A leg being immobilised, for example in a cast

  • Long journeys, particularly those lasting more than 4 hours

  • Dehydration

Having one of these risk factors does not mean that you have a DVT, but it may increase the level of concern when symptoms develop.

What should I do if I think I have a DVT?

Do not wait for a routine appointment to see whether the symptoms improve.

If you think you may have a DVT, request an urgent GP appointment or contact NHS 111.

A suspected DVT requires medical assessment and may need blood tests and an ultrasound scan of the veins. NICE uses a structured assessment of symptoms and risk factors to determine how urgently investigations and treatment are required.

How is a DVT diagnosed?

Symptoms alone cannot reliably confirm or exclude a DVT because several other conditions can cause a painful or swollen leg.

Assessment may include:

  • Your symptoms and medical history

  • Examination of the affected limb

  • Assessment of your individual risk factors

  • A blood test called a D-dimer

  • An ultrasound scan of the deep veins

Not everyone requires exactly the same combination of tests. The investigations required depend upon how likely a DVT is considered to be following clinical assessment.

Can you tell if someone has a DVT just by looking at the leg?

No.

There is no single physical sign that can safely diagnose or rule out a DVT.

Similarly, having normal pulses in the foot or a normal arterial Doppler assessment does not exclude a DVT. These assess the arterial supply bringing blood to the foot, whereas a DVT occurs within the venous system returning blood towards the heart.

A suspected DVT therefore requires appropriate medical assessment.

Is a DVT the same as phlebitis?

No.

Superficial thrombophlebitis affects a vein close to the surface of the skin. The affected vein may feel hard, tender and cord-like.

A DVT develops within one of the deeper veins.

Although they are different conditions, superficial vein thrombosis can occasionally extend towards the deep venous system, so significant or spreading symptoms should be medically assessed.

Is a DVT the same as a muscle cramp?

No.

An ordinary muscle cramp usually:

  • Starts suddenly

  • Causes a muscle to become hard and tightly contracted

  • Lasts seconds or minutes

  • Improves when the muscle relaxes or is stretched

DVT pain tends to be more persistent and may occur alongside swelling, warmth or changes in colour.

However, DVT pain can sometimes feel like cramp, which is one reason a new or unexplained persistent calf pain should not simply be assumed to be muscular.

Can cellulitis look like a DVT?

Yes.

Cellulitis can also cause a painful, hot, swollen and discoloured leg.

Other possible causes of similar symptoms include:

  • Superficial thrombophlebitis

  • Muscle injury

  • A ruptured Baker's cyst

  • Venous disease

  • Lymphoedema

  • Joint inflammation or injury

This is why diagnosis should be based on appropriate clinical assessment rather than appearance alone.

Pulmonary embolism – know the warning signs

A pulmonary embolism (PE) happens when a blood clot travels to the lungs.

Call 999 or go to A&E immediately if you have symptoms of DVT together with:

  • Sudden shortness of breath

  • Chest pain

Other concerning symptoms can include coughing up blood, collapse or fainting.

A pulmonary embolism can be life-threatening and needs emergency treatment. Do not drive yourself to A&E.

How is a DVT treated?

Treatment usually involves anticoagulant medication, sometimes referred to as a “blood thinner”.

These medicines do not literally thin the blood. They reduce the blood's ability to form and enlarge clots, allowing the body time to gradually deal with the existing clot and reducing the risk of further clotting.

Medicines used may include drugs such as:

  • Apixaban

  • Rivaroxaban

  • Edoxaban

  • Dabigatran

  • Heparin

  • Warfarin

The appropriate medicine depends upon the individual patient and their circumstances.

Treatment following a DVT commonly continues for at least 3 months, although some people require anticoagulation for longer.

Recovering after a DVT

Once treatment has begun, people are generally encouraged to remain active and walk regularly where they are able, rather than remaining unnecessarily immobile.

Your healthcare team may also advise you to:

  • Elevate the affected leg when sitting

  • Take anticoagulant medication exactly as prescribed

  • Attend any required follow-up appointments

  • Delay flights or long journeys until it is considered safe

The NHS currently advises delaying flights or long journeys until at least 2 weeks after starting anticoagulant treatment for a DVT.

If you are taking an anticoagulant, make sure doctors, dentists, pharmacists and other healthcare professionals know about it because it can affect treatment and increase bleeding risk.

Can DVT be prevented?

Not every DVT can be prevented, but you can reduce your risk by:

  • Remaining physically active

  • Avoiding sitting still for very long periods

  • Getting up and moving regularly during long journeys

  • Drinking sufficient fluids

  • Avoiding smoking

  • Maintaining a healthy weight

  • Following prescribed thrombosis-prevention measures following surgery or hospital admission

If you are at increased risk during a hospital stay or following surgery, your healthcare team may prescribe anticoagulant medication or other preventative measures.

DVT and your podiatry appointment

At Blackfords Footcare, assessment of the feet and lower limbs may sometimes identify unexpected swelling, temperature differences, colour changes or other findings which raise concern about a possible vascular problem.

However, a DVT cannot be diagnosed or safely ruled out during a routine podiatry assessment.

Importantly, a good arterial blood supply, palpable foot pulses or reassuring arterial Doppler sounds do not exclude a venous blood clot.

If your symptoms raise concern about a possible DVT, routine podiatry treatment will be deferred and you will be advised to seek urgent medical assessment.

Please do not attend a routine podiatry appointment to have a suspected DVT checked.

If you develop new unexplained pain and swelling in one leg, contact your GP urgently or NHS 111.

If this is accompanied by chest pain or shortness of breath, call 999.