Warning signs
A DVT often causes swelling, pain or tenderness, warmth, and sometimes redness in one leg (usually the calf). The symptoms are typically in one leg rather than both.
Get urgent medical advice if you have these symptoms. Seek emergency help (999) if you develop sudden breathlessness, chest pain that is worse on breathing in, or cough up blood — these can be signs of a clot on the lung.
What happens next
Assessment usually involves a clinical score, a blood test (D-dimer) and often an ultrasound scan of the leg. If a DVT is confirmed, treatment is with blood-thinning medication (anticoagulants) to stop it growing and prevent a lung clot.
Risk is increased by long periods of immobility, recent surgery, pregnancy, some medicines and certain medical conditions.
Common questions
Is a DVT an emergency?
A suspected DVT needs urgent assessment (usually the same day) but is not usually immediately life-threatening on its own. The emergency is if it causes a pulmonary embolism — sudden breathlessness or chest pain — which needs 999.
Related tools
These calculators are designed for healthcare professionals.