Thrombophilia
An increased tendency to form abnormal blood clots, either inherited or acquired. It does not cause clots by itself but raises the risk, especially in situations like surgery, pregnancy or immobility. It is investigated after an unexplained or recurrent clot, and most people with it never have a major problem.
What it is
Thrombophilia is a state in which the blood is more prone than normal to forming clots (thrombosis), usually in the veins — a deep vein thrombosis (DVT) in the leg or a pulmonary embolism (PE) in the lungs. It is not a single disease but an umbrella term for several underlying causes, which split into inherited and acquired. The commonest inherited causes are factor V Leiden and the prothrombin gene mutation, and, rarer but stronger, deficiencies of the natural clotting brakes protein C, protein S and antithrombin. The most important acquired cause is antiphospholipid syndrome, an autoimmune disorder. Importantly, thrombophilia usually raises the risk of a clot rather than causing one directly: clots tend to happen when a thrombophilia combines with a trigger such as surgery, a long flight, immobility, pregnancy, the combined contraceptive pill or HRT, or cancer. Many people carry a thrombophilia and never have a clot. It is typically investigated after an unprovoked clot, a clot at a young age, recurrent clots, clots in unusual sites, or a strong family history — and the results guide risk awareness and prevention more often than lifelong treatment.
Key lab markers
- Factor V Leiden and the prothrombin gene mutation — the commonest inherited causes.
- Protein C, protein S, antithrombin — the natural clotting brakes; a deficiency is a stronger, rarer cause.
- Lupus anticoagulant and antiphospholipid antibodies — for antiphospholipid syndrome (an acquired cause).
- D-dimer — reflects active clotting; used in diagnosing an acute clot, not the tendency itself.
- Full blood count — to look for conditions such as a high platelet count.
- Timing matters — some tests are unreliable during an acute clot or on blood thinners.
Symptoms
- Often none until a clot occurs
- A deep vein thrombosis — a swollen, painful, warm, red leg
- A pulmonary embolism — sudden breathlessness, chest pain, coughing
- Recurrent clots, or clots at a young age or unusual sites
- Recurrent miscarriage or pregnancy complications (with antiphospholipid syndrome)
- A family history of clots
Related symptoms
When to discuss with a doctor
Thrombophilia testing is not a routine screen — it is done in specific situations, such as after an unprovoked or unusual clot, a clot at a young age, recurrent clots, or sometimes a strong family history, and the timing matters because an acute clot and blood thinners can distort the results. A positive result usually means being aware of higher-risk situations (surgery, long flights, pregnancy, the contraceptive pill) and taking preventive measures, rather than automatically starting lifelong blood thinners — the decision is individualised. After a clot, the length of treatment depends on whether it was provoked and the overall picture. These are specialist judgements. Mediora.AI can bring the thrombophilia markers together so the clotting-risk pattern is visible, but interpreting them, and any decisions about testing family members, contraception, pregnancy or treatment, belong with a haematologist.