What is Deep Vein Thrombosis?
Deep Vein Thrombosis (DVT) is a condition where a blood clot forms in one of the deeper veins in your body, most commonly in the legs. While some clots are small and may not cause noticeable symptoms, others can lead to swelling, pain, and a feeling of heaviness or warmth in the affected area.
DVT is considered a serious medical condition because the clot can partially or completely block blood flow in the vein. If a piece of the clot breaks off and travels to the lungs, it can cause a pulmonary embolism (PE), a life-threatening emergency that requires immediate treatment.
That’s why it’s important to recognise the signs of DVT early and get medical advice if you notice any unusual leg symptoms, especially if you've recently been immobile, unwell, or recovering from surgery.
How Deep Vein Thrombosis develops
DVT often starts when blood flow slows down too much or becomes sluggish. This can happen for several reasons, including:
- Prolonged immobility: Sitting still for long periods (such as on long flights, car journeys, or bed rest after surgery) reduces circulation, especially in the legs.
- Injury to the vein wall: Surgery, trauma, or inflammation can damage blood vessels and trigger clotting.
- Clotting disorders: Some health conditions or inherited traits make your blood more likely to clot.
- Hormonal changes: Pregnancy, birth control pills, or hormone replacement therapy can increase clotting risk.
Most DVTs form in the deep veins of the lower leg, thigh, or pelvis, where blood has further to travel back to the heart, but it can occur anywhere on the body. When movement is limited or the veins are under strain, blood may start to pool or become thicker, creating the ideal conditions for a clot to develop.
Who is affected?
Deep Vein Thrombosis (DVT) can affect anyone, but some people are more likely to develop it due to age, lifestyle, or medical history. While DVT is often associated with older adults, it can also occur in younger people under certain circumstances.
Groups at higher risk include:
- People over 60: As we age, our circulation slows and vein walls can weaken, making clots more likely.
- Those with a family history of blood clots: If close relatives have had DVT or pulmonary embolism, your risk may be higher due to inherited clotting tendencies.
- Genetic conditions: Some people are born with traits that make their blood clot more easily, which can increase the risk of DVT.
- People recovering from surgery or injury: Especially after orthopaedic or abdominal procedures, when movement is reduced and veins may be under strain.
- Pregnant women: Pregnancy naturally increases blood volume and can press on veins in the pelvis, slowing blood flow and increasing clot risk.
- People using hormone therapies: Hormonal changes from birth control pills, hormone replacement therapy (HRT), or fertility treatments can raise clotting risk.
- Cancer patients: Certain cancers and cancer treatments can make the blood more likely to clot.
- Those with long-term illnesses: Conditions like heart failure, inflammatory disorders, or infections can increase the likelihood of developing DVT.
- People who are immobile for long periods: Whether from hospital stays, long-distance travel, or limited mobility due to other health issues.
Knowing your risk factors doesn’t mean you’ll definitely develop DVT, but it can help you and your doctor take steps to prevent it, especially during periods when you're less active or recovering from illness.
Signs and symptoms of Deep Vein Thrombosis
Deep Vein Thrombosis (DVT) can sometimes develop without obvious warning, but many people do experience symptoms that signal something isn’t quite right. These symptoms usually appear in just one leg and may start off mild before becoming more noticeable.
Common signs and symptoms
- Swelling: Typically affects one leg, especially around the calf or ankle. It may come on gradually or suddenly.
- Pain or tenderness: This may feel like cramping or soreness, often starting in the lower leg and worsening when walking or standing.
- Warmth: The skin over the clot may feel warmer than the rest of your leg.
- Red or discoloured skin: The area may look reddish, bluish, or unusually pale, especially if circulation is affected.
When symptoms may worsen
DVT symptoms tend to get worse when you’ve been sitting or lying down for long periods, such as during a long flight or car journey. The lack of movement slows your circulation, increasing the chances of clots forming or worsening an existing one.
Sometimes, the first noticeable sign of a DVT isn’t leg symptoms at all, but a serious complication like a pulmonary embolism. This happens when part of the clot travels to the lungs. It can cause sudden chest pain, difficulty breathing, or coughing up blood and needs emergency treatment.
If you’re unsure whether your leg symptoms could be serious, it’s always safest to speak to a healthcare professional promptly.
Causes and risk factors
Common causes
DVT occurs when blood flow becomes slow or uneven, allowing clots to form in the deeper veins. This is often due to a combination of reduced movement, damage to a vein, or a change in how your blood clots. Common causes include:
- Long periods of immobility: Such as sitting during travel or being on bed rest after illness or surgery.
- Surgery: Particularly operations involving the legs, hips, or abdomen.
- Injury: Direct trauma to a vein can trigger clot formation.
- Pregnancy and childbirth: The body naturally becomes more prone to clotting during pregnancy and for a short time after giving birth.
- Cancer and cancer treatment: Certain cancers and therapies can increase clotting risk by affecting blood composition.
Risk factors you should know
Knowing your personal risk factors for DVT can help you stay vigilant and make informed lifestyle choices. You may be at greater risk if you:
- Have a family or personal history of blood clots
- Are overweight or obese
- Smoke – which affects circulation and increases clotting risk
- Are over 60 – as ageing veins are more prone to clot formation
- Take hormone therapy – such as the contraceptive pill or hormone replacement therapy (HRT)
- Have long-term conditions like heart disease, lung disease, cancer or inflammatory disorders
Understanding these risk factors can help you take preventative action, especially during periods when you’re less active or unwell.
How Deep Vein Thrombosis is diagnosed
Clinical examination
Your doctor will begin with a clinical examination, checking for signs such as swelling, tenderness, warmth, redness or bluish colour in your leg. They’ll also ask about your medical history, recent travel, surgery, or any known clotting risks. This first step helps guide what tests might be needed next.
Diagnostic tests
Depending on the results of your clinical examination, your doctor may require further tests to confirm if you have a DVT. The most common diagnostic tests for DVT are:
- D-dimer test: Detects substances released when a clot breaks down. A raised D-dimer level can suggest a clot is present, but this isn’t always conclusive on its own and may be followed by imaging.
- Duplex ultrasound: This is the most common and reliable way to detect DVT. It uses sound waves to create images of the veins in your leg, showing where blood flow might be blocked or slowed by a clot.
- Venogram or MRI scan: These are used less often but may be needed in complex cases or if ultrasound results are unclear. More commonly used on the abdomen or brain. A venogram involves injecting dye into a vein to get detailed X-ray images.
Treatment options for Deep Vein Thrombosis
Once DVT is confirmed, your treatment will depend on the size and location of the clot, your overall health, and your risk of complications. Some people require urgent treatment, while others may be managed with close monitoring and lifestyle changes.
Medication
- Anticoagulants (blood thinners): These are the most common treatment for DVT. They don’t break down existing clots but help stop them from getting bigger and reduce the risk of new clots forming. You might take these as tablets, injections, or both depending on your needs.
- Thrombolytics: These are powerful clot-dissolving drugs usually used in hospital settings for severe or life-threatening clots. They’re typically given via a drip into your vein.
Surgical options
- IVC filter: If you can’t take blood thinners, a small device called an inferior vena cava (IVC) filter might be placed in a large vein in your abdomen to stop clots from reaching your lungs.
- Thrombectomy: This is a surgical procedure to physically remove the clot. It’s rarely needed but may be considered in emergency situations or when a large clot is blocking major blood flow.
When is conservative management most appropriate?
Not all DVTs require aggressive treatment. If the clot is small and not causing severe symptoms, your doctor might recommend a more conservative approach. This could include:
- Regular monitoring: Keeping a close eye on symptoms and using repeat scans to track any changes.
- Compression stockings: These help support blood flow in your legs and reduce the risk of swelling and long-term complications like post-thrombotic syndrome.
- Lifestyle changes: Staying active, keeping hydrated, avoiding long periods of immobility, and maintaining a healthy weight are all important for recovery and prevention.
Your doctor will work with you to decide the safest and most effective treatment based on your individual risk factors and preferences.
What to expect during and after treatment
During your treatment
If you're diagnosed with a Deep Vein Thrombosis (DVT), treatment usually starts straight away to reduce the risk of the clot getting bigger or travelling to your lungs. Most people begin treatment with anticoagulant medication, also known as blood thinners. These help stop new clots from forming and prevent existing ones from growing.
You may also be asked to wear compression stockings, which help improve blood flow in your legs and reduce swelling. Some people can safely manage their treatment at home, especially if their symptoms are mild and they’re otherwise well. In other cases, such as if the clot is large, painful, or at risk of complications, hospital care may be needed to start treatment under close supervision.
Aftercare and recovery
Recovery from DVT varies from person to person, but most people will need to take blood thinning medication for at least 3 to 6 months. Your doctor will explain how long you’ll need this based on the size and location of the clot, your risk of another clot, and whether any underlying conditions were involved.
You’ll likely have regular follow-up appointments to monitor your progress, adjust your medication if needed, and check for signs of complications. During recovery, it’s important to:
- Stay active: Gentle movement, like walking, helps prevent further clots.
- Elevate your legs: This can ease swelling and help blood flow return to normal.
- Follow your medication plan: Missing doses can increase your risk of complications.
- Wear compression stockings: If advised, they can help reduce long-term issues like post-thrombotic syndrome.
Follow-up and long-term care
After your initial treatment, your doctor will continue to support you through the recovery process. Depending on your risk factors, they may suggest:
- Longer-term use of blood thinners: Particularly if you’ve had more than one clot or have a medical condition that increases your risk.
- Repeat imaging or blood tests: To check if the clot has gone and to look for any signs of damage to the veins.
- Lifestyle advice: This might include weight management, stopping smoking, and staying active to help reduce your chances of another DVT.
Preventing recurrence is a key part of your long-term care. Your healthcare team will work with you to create a plan that supports your recovery and lowers your risk of future clots.
Preventing Deep Vein Thrombosis
DVT can sometimes develop without warning, but there are simple steps you can take to lower your risk—especially if you’ve had a clot before, are recovering from surgery, or sit for long periods.
Lifestyle tips
Keeping your blood flowing well is one of the best ways to prevent clots from forming. Here are some everyday actions that can make a big difference:
- Move regularly: Avoid sitting or standing still for too long. Try to stretch your legs every hour, especially on long journeys or during desk work.
- Stay hydrated: Drinking enough water helps keep your blood from becoming too thick, which can increase the risk of clotting.
- Maintain a healthy weight: Extra weight puts pressure on your veins and slows blood flow, particularly in the legs.
- Avoid smoking: Smoking damages your blood vessels and increases your risk of clotting.
- Use compression stockings: If advised by your doctor, these can improve blood flow in your legs and reduce swelling, especially during travel or recovery from surgery.
Early intervention
If you’re preparing for surgery, have a long hospital stay planned, or have known risk factors (like a previous DVT, clotting disorder, or family history), speak with your healthcare provider ahead of time. They may recommend:
- Temporary blood thinning medication: To reduce your risk during times of limited movement.
- Compression therapy: Especially helpful after operations or during travel.
- Movement plans: Guidance on gentle exercises to keep your circulation healthy during recovery.
Being proactive can help prevent a serious complication before it starts.
When to seek medical advice
Signs you shouldn't ignore
Recognising the signs of a DVT early is vital. Don’t wait—get medical help immediately if you notice any of the following symptoms, especially in just one leg:
- Sudden swelling: Your leg (or part of it) becomes noticeably larger than the other.
- Pain or tenderness: Often felt in the calf or thigh and may worsen when walking or standing.
- Warm skin: The area over the clot may feel warm to the touch.
- Red or discoloured skin: A patch of redness that doesn’t go away could be a sign of inflammation or clotting.
You should also seek urgent medical help if you develop:
- Chest pain or tightness
- Sudden shortness of breath
- Coughing up blood
These can be signs that a clot has travelled to your lungs, a life-threatening condition called a pulmonary embolism.
