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Health condition · Clinically reviewed

Blood clots, DVT and PE, DOACs and the modern thrombosis toolkit.

Venous thromboembolism is common, treatable and, done well, largely preventable. A modern pathway pairs DOACs with catheter therapy for the biggest clots.

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Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against NICE NG158, BTS, ESC and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK guidance including DOAC first-line therapy and catheter-directed thrombolysis.

Key facts

Blood clots at a glance.

The essentials, in plain English: what a VTE is, what drives it, and how it is treated in the UK today.

  • What it is

    Venous thromboembolism (VTE) covers deep vein thrombosis (DVT), pulmonary embolism (PE) and rarer clots in cerebral, abdominal or upper-limb veins.

  • Virchow’s triad

    Three drivers of clotting: venous stasis, hypercoagulability and endothelial injury. Most clots involve at least two.

  • Common triggers

    Surgery (orthopaedic hip and knee highest), trauma, immobility, cancer, oestrogen (pill, HRT, pregnancy, IVF), long-haul flight and inherited thrombophilia.

  • Foundation therapy

    Direct oral anticoagulants (apixaban, rivaroxaban, edoxaban, dabigatran) are first-line for most DVT and PE under NICE NG158.

  • Duration

    Provoked-transient 3 months, provoked-persistent indefinite, unprovoked usually 6 months minimum, cancer-associated 6+ months.

  • Emergency

    Massive PE with haemodynamic collapse needs systemic or catheter-directed thrombolysis and, rarely, ECMO.

Why this guide matters

One clot, many sites, one framework.

DVT in the leg, PE in the lungs, sinus thrombosis in the brain and portal or Budd-Chiari clots in the abdomen all share the same biology and, largely, the same treatment principles.

  • Virchow’s triad still explains it

    Stasis, hypercoagulability and endothelial injury: nearly every case ties back to at least two of these three drivers.

  • DOACs changed the day-to-day

    Fixed dosing, no routine INR monitoring and rapid onset make apixaban and rivaroxaban the default outpatient therapy.

  • Interventional care rescues the sickest

    Catheter-directed thrombolysis and mechanical thrombectomy salvage limbs, lungs and lives when clot burden is huge.

How the diagnosis is made

From first symptom to a confirmed clot.

The steps a UK emergency team or thrombosis clinic will normally follow, in order, so you know what to expect and why.

  1. 01

    Assessing

    Wells score and PERC

    A structured probability score for DVT or PE, combined with PERC rule-out for low-risk patients in the emergency department.

  2. 02

    Assessing

    D-dimer, age-adjusted

    A negative age-adjusted D-dimer (over-50s: age × 10 µg/L) rules out VTE in low-probability cases without imaging.

  3. 03

    Assessing

    Bloods and background

    FBC, coagulation, LFTs, renal function and a malignancy review appropriate for age and symptoms.

  4. 04

    Confirming

    Compression ultrasound for DVT

    Doppler ultrasound of the leg (or arm) is the gold-standard first test for suspected deep vein thrombosis.

  5. 05

    Confirming

    CTPA or V/Q for PE

    CT pulmonary angiogram is the gold standard for PE; V/Q scan is preferred in pregnancy and severe renal impairment.

  6. 06

    Confirming

    MRV for cerebral sinus thrombosis

    MR venography (or non-contrast MRI) confirms cerebral venous sinus thrombosis (CVST) in patients with headache, seizure or focal deficit.

  7. 07

    Preparing

    Risk stratification and thrombophilia

    BNP, troponin and echo grade PE severity (PESI). Selective thrombophilia screening in young, recurrent, unusual-site or familial cases (timed off anticoagulation).

Typical timeline: first presentation to a treated, confirmed diagnosis in hours, not days.

Symptoms

What a blood clot actually feels like.

Presentation depends on where the clot is: leg, lung, arm, brain or abdomen. These are the classic patterns and the features that mean act now.

  • Unilateral leg swelling

    Swelling, warmth, redness and calf or thigh tenderness along a deep vein: the classic DVT presentation.

  • Sudden breathlessness

    Acute dyspnoea, pleuritic chest pain, tachycardia and sometimes haemoptysis: think pulmonary embolism.

  • Syncope or collapse

    Fainting or circulatory collapse can be the first sign of a massive, haemodynamically significant PE.

  • Swollen arm

    Subclavian or axillary DVT: think Paget-Schroetter (effort thrombosis) or a central venous catheter.

  • New severe headache

    Persistent headache with seizure, focal deficit or papilloedema can indicate cerebral venous sinus thrombosis (CVST).

  • Abdominal pain

    Mesenteric, portal, splenic or Budd-Chiari (hepatic vein) thrombosis can present with abdominal pain, ascites or deranged LFTs.

  • Tender superficial vein

    A red, cord-like, tender superficial vein suggests superficial thrombophlebitis; long segments may still need anticoagulation.

  • Red flag – collapse or hypoxia

    Any collapse, hypoxia or new right-heart strain demands immediate hospital assessment for massive PE.

Treatment

How blood clots are treated in the UK.

DOAC anticoagulation for most, LMWH in pregnancy and cancer, and catheter-based thrombolysis or thrombectomy when clot burden is large.

  • DOAC first-line

    Apixaban, rivaroxaban, edoxaban or dabigatran cover most DVT and PE (see /treatments/dvt-clinic/). Simple monitoring and predictable dosing.

  • Low-molecular-weight heparin

    LMWH (dalteparin, enoxaparin) remains the anticoagulant of choice in pregnancy and often for cancer-associated thrombosis.

  • Warfarin with bridging

    Reserved for antiphospholipid syndrome, mechanical valves, severe renal impairment or DOAC intolerance. INR monitoring required.

  • Systemic thrombolysis

    Alteplase for massive PE with haemodynamic instability; considered selectively in submassive PE (PEITHO trial evidence is mixed).

  • Catheter-directed thrombolysis

    CDT, AngioJet, EKOS ultrasound-facilitated and Inari FlowTriever mechanical thrombectomy for iliofemoral DVT and selected PE.

  • IVC filter

    Selective use when anticoagulation is contraindicated or fails. Retrievable filters should be removed once safe to anticoagulate.

  • Surgical decompression

    First rib resection for Paget-Schroetter; TIPS or liver transplant for Budd-Chiari; specialist stroke care for CVST.

  • Prophylaxis and lifestyle

    Hospital and surgical VTE prophylaxis (Caprini or Padua score), compression stockings, mobilisation, hydration, weight and smoking cessation.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your GP, haematologist or thrombosis team knows your history and can tell you which parts apply to you. If in doubt, get seen.

  • NICE. Venous thromboembolic diseases: diagnosis, management and thrombophilia testing (NG158).

  • British Thoracic Society (BTS). Guideline for the initial outpatient management of pulmonary embolism.

  • European Society of Cardiology (ESC). Guidelines on the diagnosis and management of acute pulmonary embolism.

  • Thrombosis UK. Patient information on DVT, PE and long-term anticoagulation.

Red flags

When a blood clot needs urgent attention.

Most VTE can be managed as an outpatient. These are the situations that cannot, and where a specialist opinion is needed the same day.

  • Massive PE with collapse

    Sudden syncope, hypotension or cardiac arrest: call 999. Systemic thrombolysis or catheter-directed therapy is time-critical.

  • Suspected iliofemoral DVT

    Whole-leg swelling with severe pain (phlegmasia) risks limb loss and may need urgent thrombectomy or thrombolysis.

  • Cerebral venous sinus thrombosis

    Severe headache with seizure, focal deficit or reduced consciousness needs urgent CT/MRV and specialist stroke input.

  • Post-partum or late pregnancy leg pain

    VTE risk is highest around delivery and the six-week post-partum window: low threshold for imaging and LMWH.

  • VITT after adenoviral vaccine

    Rare vaccine-induced immune thrombotic thrombocytopenia: unusual-site clot with low platelets needs non-heparin anticoagulation and IVIg.

  • Abdominal pain with ascites

    New Budd-Chiari or portal vein thrombosis can mimic gastro disease: image early if LFTs or clotting are deranged.

  • Bleeding on anticoagulation

    Major bleeding, black stools or new bruising while on a DOAC or warfarin needs same-day assessment.

  • Recurrent clot on treatment

    A new clot despite adequate anticoagulation raises the possibility of cancer, APS or drug interaction: escalate.

  • Unusual-site or unprovoked in the young

    Splanchnic, cerebral or upper-limb clots in under-50s warrant thrombophilia, JAK2 and myeloproliferative screening.

Living with it

A treatable condition, with a clear ladder.

Four things that make the biggest difference after a VTE: take the anticoagulant on time, keep moving, know your warning signs and review duration every year.

A quiet reminder

Consistency beats intensity, every time.

Small, steady habits, kept up for months, do more than a heroic week that does not last. Thrombosis UK offers excellent long-term patient support.

  1. 01 Rhythm

    Take the anticoagulant every day

    DOACs work in narrow time windows. A missed dose is a real gap in protection: set an alarm and keep a spare pack.

  2. 02 Movement

    Move, hydrate, compress

    Walking, hydration and graduated compression stockings reduce post-thrombotic syndrome after a proximal DVT.

  3. 03 Flags

    Know your bleeding and clot signs

    Report black stools, heavy bruising or new one-sided swelling or breathlessness the same day.

  4. 04 Review

    Annual reassessment

    Duration is not always three months: unprovoked, cancer or persistent-risk clots need yearly benefit-versus-bleeding review.

Frequently asked

Everything we get asked about blood clots.

Quick answers on diagnosis, DOACs, duration, thrombolysis and pregnancy.

  • What is a blood clot (VTE)?

    Venous thromboembolism (VTE) is an umbrella term for deep vein thrombosis (DVT) and pulmonary embolism (PE), plus rarer clots in cerebral, abdominal or upper-limb veins. They form when Virchow’s triad of stasis, hypercoagulability and endothelial injury tips into pathological clotting.

  • How is a DVT or PE diagnosed?

    A Wells score guides likelihood. Low-probability cases are ruled out with an age-adjusted D-dimer. Compression Doppler ultrasound confirms DVT; CT pulmonary angiogram (CTPA) confirms PE, with V/Q scan as an alternative in pregnancy or renal impairment.

  • Are DOACs really first-line?

    Yes. NICE NG158 recommends apixaban or rivaroxaban as first-line for most DVT and PE, with edoxaban and dabigatran as alternatives. Warfarin remains preferred in antiphospholipid syndrome, mechanical valves and severe renal impairment, and LMWH in pregnancy.

  • How long do I need to be on anticoagulation?

    Provoked by a transient risk (surgery, plaster cast): usually three months. Provoked by persistent risk (active cancer, chronic disease): indefinite with annual review. Unprovoked: at least six months, then individualised. Cancer-associated: six months or longer.

  • When is thrombolysis or thrombectomy used?

    Systemic thrombolysis with alteplase is reserved for massive PE with haemodynamic instability. Catheter-directed thrombolysis, EKOS or mechanical thrombectomy (for example Inari FlowTriever) is considered for large iliofemoral DVT and selected intermediate-risk PE in specialist centres.

  • What about pregnancy?

    VTE risk rises through pregnancy and peaks in the six-week post-partum period. Low-molecular-weight heparin (dalteparin or enoxaparin) is used throughout: warfarin and DOACs are not safe in pregnancy or breastfeeding.

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