Deep vein thrombosis (DVT) is a blood clot in a deep vein, usually in a leg. It needs prompt medical assessment because part of the clot can travel to the lungs and cause a pulmonary embolism.
Symptoms
DVT often affects one leg. Symptoms can include:
- Throbbing or cramping pain, commonly in the calf or thigh
- Swelling in one leg
- Warm skin around the painful area
- Red or darkened skin
- Swollen veins that feel hard or sore
DVT can occur without obvious symptoms. Similar symptoms may have other causes, so a healthcare professional must make the diagnosis.
When to Get Emergency Help
Call your local emergency number immediately if symptoms of DVT occur with sudden breathlessness, chest pain that may be worse when breathing in, coughing up blood, a very fast heartbeat or fainting. These may be signs of a pulmonary embolism.
Risk Factors
Risk increases after an operation or hospital stay, during long periods of limited movement and on journeys lasting several hours. Other factors include pregnancy, recent childbirth, cancer, smoking, obesity, previous DVT, some inherited clotting conditions and medicines that contain oestrogen.
Diagnosis
A healthcare professional will assess the symptoms and risk factors. Tests may include a D-dimer blood test and an ultrasound scan of the affected limb.
Treatment
DVT is usually treated with anticoagulant medicine. These medicines reduce the blood’s ability to clot and help prevent the clot from growing or travelling to the lungs. The type of medicine and length of treatment depend on the person’s circumstances. Anticoagulants can cause bleeding, so follow the prescribing instructions and seek medical advice about unusual bleeding.
Reducing Risk
Move as soon as it is safe after illness or surgery, avoid sitting still for long periods and follow any prevention plan given by a healthcare professional. On a long journey, get up when possible, move the feet and ankles and drink water. Compression stockings or preventive medicine should be used only when recommended for you.
Sources
Reviewed 28 August 2026.