Thrombophilia testing in venous thromboembolism: When, who and why it matters. A practical review

• One should only test for thrombophilia when results would change management. • Anticoagulation is context-driven in most thrombophilias. • Antithrombin deficiency and antiphospholipid syndrome mandate specific treatment choices. • DOAC interference mandates activated charcoal or washout before testing (except genetic tests). • Transdermal oestrogen and progestin-only contraception are safe for women with thrombophilia. Thrombophilia encompasses inherited and acquired biological abnormalities that predispose to venous thromboembolism (VTE). Although thrombophilia testing has been available for decades, routine screening of all patients presenting with deep vein thrombosis or pulmonary embolism is neither recommended nor cost-effective. Current international guidelines support testing for clinical scenarios where results may meaningfully inform recurrence risk and thereby influence therapeutic decisions regarding anticoagulation duration, anticoagulant choice, contraceptive counselling or pregnancy management. This narrative review provides a practical, evidence-based framework for thrombophilia investigation. We address testing indications stratified by clinical context, including unprovoked VTE in young patients, hormone-associated thrombosis and unusual-site thrombosis. Practical considerations for testing timing and anticoagulant interference are detailed, including recent expert guidance on charcoal-based direct oral anticoagulant neutralization strategies. Therapeutic implications are examined across specific populations: women requiring hormonal contraception or menopause hormone therapy, cancer-associated thrombosis and chronic thromboembolic pulmonary hypertension. Thrombophilia results should be interpreted within the broader clinical context. A clinical decision algorithm synthesizing current evidence and recommendations is proposed to guide selective testing.