DVT symptoms: How to recognise a blood clot in your leg early

Deep vein thrombosis (DVT) is a potentially life-threatening condition where a blood clot forms in a deep vein—typically in the leg. Although the symptoms may be subtle at first, early detection is vital to prevent complications such as pulmonary embolism. Knowing how to identify DVT symptoms, especially in the leg, can help you act quickly and avoid long-term damage. In this guide, we explain how DVT presents itself, who is most at risk, and what you should do if you suspect a clot.

What is DVT?

DVT occurs when a blood clot (thrombus) forms in one of the body's deep veins, often in the lower leg or thigh. This clot can partially or completely block blood flow, leading to swelling, pain, and even skin changes. If part of the clot breaks off and travels to the lungs, it can result in a pulmonary embolism—a medical emergency.

We explain this more thoroughly in our article on what is thrombosis? Everything you need to know about blood clots in the legs.

Common Symptoms of DVT in the Leg

1. Swelling – often only in one leg

One of the most recognisable symptoms of DVT is swelling that affects just one leg, typically in the calf or thigh. This happens because the blood clot obstructs normal circulation, causing fluid to build up in the surrounding tissues. The leg may feel tight, heavy, or unusually warm.

As we explain in our article on swollen feet, ankles, and legs: causes, treatments, and when to worry, one-sided swelling is a red flag that should never be ignored.

2. Pain or tenderness in the leg

Pain from DVT often feels like a persistent cramp or deep ache, usually in the calf. It may intensify when walking, standing, or flexing the foot upwards. Unlike typical muscle soreness, this discomfort does not ease with rest or stretching.

3. Skin discolouration

Changes in skin tone—such as redness, blue tints, or darker patches—can signal a problem with deep vein circulation. The skin may also feel warmer than usual or appear shiny or stretched.

We describe how to distinguish these changes in our article on leg oedema: what it is and how it can be treated, which discusses underlying venous issues that affect the skin.

4. Suddenly visible or bulging veins

Sometimes, the veins near the surface of the leg become more prominent as the body reroutes blood flow around the blocked deep vein. These veins may look swollen, twisted, or darker than normal.

In our article why are my veins so visible all of a sudden?, we go into detail on when newly visible veins may indicate a deeper issue like DVT.

5. Localised warmth or heat

A warm area on the leg that is also tender or swollen could be a sign of inflammation caused by a blood clot. This symptom is often overlooked but can be an early indicator of DVT, especially when combined with other signs.

When Should You Seek Medical Help?

If you experience symptoms such as swelling, pain, warmth, or visible veins in just one leg, you should seek medical attention promptly. A doctor can assess your symptoms and perform appropriate testing, such as an ultrasound or blood test, to confirm the presence of a clot.

We cover related underlying causes in our article on venous insufficiency: symptoms, causes, and treatments, which can increase your risk of DVT if left unmanaged.

Who Is Most at Risk of DVT?

While anyone can develop DVT, certain factors significantly raise your risk:

• Extended periods of immobility (e.g. flying long distances or bed rest after surgery)
• Pregnancy or recent childbirth
• Use of hormone-based medications, such as birth control pills or HRT
• Smoking
• Obesity
• Family or personal history of blood clots
• Chronic vein conditions like varicose veins or venous insufficiency

Understanding your personal risk factors is essential for prevention and early action.

How Is DVT Diagnosed?

The diagnostic process for DVT often starts with a clinical examination. If a clot is suspected, a Doppler ultrasound is typically used to check for restricted blood flow. In some cases, blood tests (e.g. D-dimer) or imaging such as CT scans may be required for confirmation.

Treatment generally involves blood thinners (anticoagulants) to prevent the clot from growing or moving. Depending on your symptoms, compression stockings may also be recommended to support circulation and reduce the risk of long-term complications like post-thrombotic syndrome.

How Can You Prevent DVT?

DVT is often preventable, especially if you're aware of your risk and take simple but effective steps:

• Move your legs regularly, especially on long journeys or during recovery after surgery
• Stay hydrated throughout the day
• Avoid smoking and maintain a healthy weight
• Use compression stockings when advised by a healthcare provider
• Follow up on chronic vein issues or family history of blood clots with your GP

Conclusion

DVT symptoms are often subtle, but they can escalate quickly if ignored. Swelling, tenderness, discolouration, and visible veins in one leg are not just cosmetic concerns—they may indicate a serious underlying problem. If you notice these signs, don’t wait. Speak with a medical professional to get a diagnosis and begin treatment early.

‍