Deep Vein Thrombosis (DVT) in the Leg: Symptoms, Causes, and Treatment

Concerned about symptoms like swelling, leg pain or unexplained warmth in your calf? In this guide, we explain how to recognise a blood clot in the leg—also known as deep vein thrombosis (DVT)—what causes it, how it's treated, and when to seek urgent care.

At UK Vein Care, we regularly help patients identify and manage conditions like DVT. With decades of experience in diagnosing and treating vein-related disorders, our clinic is one of the UK’s most trusted providers for patients suffering from varicose veins, spider veins, and related complications. We combine advanced diagnostics, personalised care, and vascular expertise to ensure each patient receives effective treatment with minimal delay.

Learn more about varicose veins and how they can signal underlying venous issues. We also explain spider veins and treatment options in our dedicated guide.

What Are the Symptoms of a Blood Clot in the Leg?

Recognising the signs of a DVT early is critical. Common symptoms include:

• Swelling, usually in one leg, especially around the calf or thigh.
• A persistent, cramping-like pain, worsened by standing or walking.
• Redness or warmth over the affected area.
• Visible surface veins, sometimes more prominent than usual.
• In some cases, numbness or tingling, indicating impaired circulation.

If you’re asking yourself how a blood clot in the leg feels, most patients describe it as a dull, constant pain—deeper than a muscle strain and unrelieved by rest. The discomfort tends to escalate and localise to one leg.

The Danger of Leaving a Blood Clot Untreated

When left untreated, DVT can lead to pulmonary embolism (PE)—a potentially life-threatening condition where the clot travels to the lungs. Research published in The Lancet confirms the high mortality risk associated with undiagnosed or unmanaged DVT, reinforcing the need for early evaluation and treatment.

Superficial Clots: What Is Thrombophlebitis?

Thrombophlebitis refers to inflammation of a surface-level vein caused by a clot. While less dangerous than DVT, symptoms can include tenderness, localised redness, and skin warmth. Unlike a bruise, a superficial clot is often painful and long-lasting.

What Causes a Blood Clot in the Leg?

Numerous factors can contribute to DVT:

• Prolonged immobility – such as during long flights or recovery from surgery.
• Recent operations, especially orthopaedic or pelvic.
• Genetic mutations, such as Factor V Leiden, which affect clotting mechanisms.
• Hormonal changes, including pregnancy or HRT.
• Smoking and obesity, both of which impair vascular health.
• Varicose veins – which can indicate underlying venous insufficiency.

You can read more about how varicose veins affect your circulation in our guide to varicose veins treatment.

The Link Between Varicose Veins and DVT

Although varicose veins themselves are not dangerous, they are often a visible sign of poor venous function. Damaged valves in surface veins can increase pressure and reduce the efficiency of blood return, promoting stasis—a key component in clot formation.

Studies in the European Journal of Vascular and Endovascular Surgery suggest that this environment can raise the risk of deeper clot formation. When varicose veins coincide with other risk factors like inactivity or genetic predisposition, the likelihood of DVT increases.

Diagnosis and Treatment

DVT is typically diagnosed using:

• Ultrasound, to visualise blood flow and detect obstruction.
• D-dimer tests, which assess the presence of clot-related proteins.
• Venography, an imaging technique using contrast dye.

Treatment depends on severity but usually involves:

• Anticoagulants, such as warfarin or newer oral options, to stop clot growth.
• Thrombolytics, for rapid clot dissolution in emergencies.
• Compression stockings, to promote circulation and reduce swelling.

Understanding Post-Thrombotic Syndrome (PTS)

Even after a blood clot is treated, some patients experience long-term complications—a condition known as post-thrombotic syndrome (PTS). This occurs when the clot damages vein valves, leading to chronic symptoms such as leg pain, swelling, skin discolouration, and in severe cases, venous ulcers.

PTS can significantly affect quality of life. It may make everyday activities like walking or standing for extended periods uncomfortable or even painful. To reduce the risk of PTS, early treatment of DVT is essential, along with consistent use of compression stockings and proper follow-up with a vein specialist.

How to Lower Your Risk

Proactive steps include:

• Moving regularly, especially during long periods of sitting.
• Wearing compression stockings on flights or during recovery.
• Maintaining a healthy lifestyle, with regular exercise and weight control.

Studies from the Journal of Cardiovascular Research affirm that even moderate physical activity significantly reduces thrombotic risk.

Conclusion

DVT is a serious medical issue, but with the right knowledge and prompt care, its risks can be managed. Understanding early symptoms, knowing your personal risk, and acting quickly can prevent complications. At UK Vein Care, we’re here to support you with timely diagnosis, professional treatment, and ongoing care for your vein health.