Anticoagulant Therapy For Deep Vein Thrombosis

  • Dr Kiana Bamdad Bachelor of Medicine, Bachelor of Surgery - MBBS, Medicine, Cardiff University / Prifysgol Caerdydd
  • Pauline Rimui BSc, Biomedical Science, University of Warwick, UK

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Deep vein thrombosis (DVT) is a medical condition characterised by the formation of blood clots within deep veins.1 Anticoagulant therapy becomes an invaluable ally in the fight against DVT, helping to stop these potentially fatal blood clots from forming and spreading.2 In this article, we explore the complexities of DVT, comprehending its causes and consequences, before focusing on the field of anticoagulants, drugs intended to thin blood and prevent the dangerous growth of clots.

What is deep vein thrombosis?

Deep vein thrombosis (DVT) is a blood clot that forms in deep veins. It usually forms in the leg but can form in the arms too.1 To treat DVT and reduce its negative effects, early detection and clinical intervention are crucial. It also helps rule out DVT in healthy individuals, reducing the expense and risk of anticoagulant medication.3

The severity of DVT can be classified as follows:1

  • Provoked: As a result of acquired conditions, use of certain medications and/or long period of immobility – trauma, obesity, cancer, hormonal medication such as oral contraceptive pills, recent long haul flight, bed bound, etc.
  • Unprovoked: Occurring for unknown or internally derived causes -  in these cases, discontinuing anticoagulation increases the risk of recurrence
  • Proximal: Occurs above the knee, affecting femoral or iliofemoral veins; much higher chance of complications to occur (e.g. pulmonary embolism)
  • Distal: Below the knee

Understanding DVT

Risk factors considered to be causes of DVT:1

  • Slow/reduced blood flow – Limited movement (long flights, bed rest, anaesthesia, stroke)
  • Increased pressure in veins - A reduction in vein flow caused by mechanical compression or functional impairment
  • Oestrogen – birth control pills or hormone therapy4
  • During pregnancy and up to 6 weeks post pregnancy4
  • Recent surgery4

 Factors that increase the risk of DVT4:

  • Cancer
  • Genetic blood disorders
  • Older age
  • Being overweight/obese
  • Personal history of DVT
  • Family member who has had DVT

Pulmonary embolism

A pulmonary embolism is a complication that can occur with DVT. A pulmonary embolism (PE) is where an embolus (loose clot) travels through the bloodstream and reaches the lungs. PEs are treatable but a large PE can be life-threatening as it can block blood flow to the lungs.4

Symptoms of PE can include:4

  • Sudden shortness of breath
  • Pain when breathing in deeply
  • Heart beating fast
  • Coughing up blood
  • Feeling lightheaded
  • Fainting


  • Lots of DVTs usually resolve without any complications
  • There is a high risk of DVT recurrence – up to 25%
  • In approximately 6% of DVT cases, death occurs

Role of anticoagulant therapy

Anticoagulant drugs are used to prevent or treat blood clots by inhibiting coagulation. There is something called the coagulation cascade, which is a series of steps that occur in forming blood clots after an injury. Anticoagulants work by interfering with the coagulation cascade at various points.2,5 So, in DVT, anticoagulants are used to prevent clots from forming and prevent or cure recurrent thrombosis.2

Types of anticoagulant therapies used in DVT treatment:2,5

Selection of anticoagulants

Initial treatment options:

For the acute treatment (0 ~ 7 days) these anticoagulants are used:1,6

  • UFH – affects clotting cascade
  • LMWH – also affects the clotting cascade
  • DOACs – used as an alternative as it has similar effects

For long-term treatment (~7 days to ~3 months) these anticoagulants are used:1,6

  • DOACs
  • Warfarin (VKA) – requires frequent monitoring5

Anticoagulant complications

Complications that can occur with the use of anticoagulants can be anticoagulant or patient-related.5

Anticoagulant related:5

  • Higher risk of significant bleeding with warfarin than DOACs
  • Anticoagulant dose
  • Concomitant use of other drugs or particular foods that separately raise the risk of bleeding, such as antiplatelet medicines, and use of cranberry and grapefruit juice with warfarin

Patient-related risks:5

  • Age
  • Underlying medical conditions
  • Race – increased risk in black/brown people
  • Recent surgery

Contraindications of anticoagulant use

If patients have the following conditions, anticoagulation should be avoided:5

  • Major trauma
  • Recent major surgeries
  • Active bleeding

With the following conditions, anticoagulation may be used:5

  • Surgeries with low risk
  •  Aortic dissection or aneurysm
  • Gastrointestinal bleed

Cautious use in the following patients:5

  • Pregnant patients
  • Elderly patients - particularly those at risk of recurrent falls

Monitoring and adjusting therapy

Once DVT has been diagnosed, the patient undergoes anticoagulant treatment for 3 – 6 months. Recurrent episodes may require ~ 12 months of treatment. They are monitored by a haematology nurse or a pharmacist, where the INR (international normalised ratio) is monitored. Patients also need to be monitored for any bleeding.1

Patients on anticoagulation who are suspected of bleeding are closely monitored on their:5

  • Haemoglobin
  •  Blood pressure
  •  Heart rate
  •  Electrocardiogram
  •  Indicators of internal bleeding – flank, back, or joint pain
  • Change in urine colour – smoky or dark
  • Change in bowel movement colour - dark, which indicates the presence of melena

Patient management and education

Patients should be educated on the condition and be made aware of any risks and how to minimise them. They should wear compression socks and as a lifestyle change discontinue smoking if they smoke.1 Patients should also be encouraged to move around independently.5

Special considerations

Anticoagulant therapy in pregnancy

The use of anticoagulants throughout pregnancy and the postpartum period should be closely monitored in women who are expecting. When selecting an anticoagulant medication, the benefits and risks to the mother and foetus should be taken into consideration as no anticoagulant therapy can be used and be risk-free.7

Warfarin carries the risk of bleeding in the foetus and mother, especially during late pregnancy and delivery. Parenteral heparin has the advantage of being unable to cross the placental barrier but it can still be a reason for bleeding problems in pregnancy. Parenteral heparin also carries problems of bone demineralisation in the mother with long-term use.7

For therapeutic and prophylactic anticoagulation, low molecular weight heparin can be used in pregnancy. It has improved bioavailability, a longer half-life, and a reduced risk of thrombocytopenia and osteoporosis. The rationale for using LMWH in pregnancy can be based on previous studies that have shown LMWH to be as effective and safe as unfractionated heparin.7

Anticoagulant therapy in cancer patients

Patients with cancer have a higher risk of bleeding episodes and venous thromboembolism (VTE). Normally, low molecular weight heparin (LMWH) is the preferred treatment for VTE in cancer patients. Compared to warfarin, LMWH has been shown to reduce the risk of VTE. DOACs have also been shown to reduce the risk of VTE.8

Patients with cancer should be individually assessed for the length of anticoagulation based on factors such as cancer type, staging, activity, treatment, life expectancy, and whether the patient has an active disease or is in remission, given the high risk of recurrence.9


Deep Vein Thrombosis (DVT) is a serious condition that can become life-threatening if not treated early. It is a condition where blood clots form deep in the vein, commonly in the legs. To treat DVT anticoagulants are used, such as warfarin and DOACs. As with all drugs, there are risks so be aware of what risks each drug carries. Pregnant people and people with cancer should have special considerations made when using anticoagulants. Some things patients can do to manage DVT is to move around a lot and not remain inactive for prolonged periods of time. 


What is DVT?

Deep vein thrombosis (DVT) is a medical condition that is characterised by the formation of blood clots within the deep veins especially in the legs. These clots can cause serious health risks as they can dislodge and make their way to vital organs and create blockages hindering the normal function of those organs.

What is the first-line treatment for DVT?

Anticoagulant therapy.1

What is anticoagulant therapy, and how does it work to treat DVT?

The drugs used in anticoagulant therapy help prevent blood clot formation and growth. The aim of using these medications are to reduce the formation of new blood clots and reduce the risks posed by DVT complications such as pulmonary embolisms.

What anticoagulants are used for DVT?

Commonly used anticoagulants for DVT include unfractured heparin and low molecular weight heparin, warfarin, DOACs.6

How long do you need to be on anticoagulants for DVT?

Initially 3 to 6 months with longer treatment up to 12 months.6 However, treatment is dependent on several variables such as severity of the clots, presence of risk factors and other individual patient characteristics. 

Are there any risks or side effects associated with using anticoagulant therapy for DVT?

Yes, there are certain risks of anticoagulant therapy include increased risk of bleeding, bruising and gastrointestinal discomfort. Other rarer cases include allergic reactions or severe bleeding. Patients are, therefore, recommended to be monitored regularly for any signs of these side effects or other complications that arise from the use of anticoagulant medications.

What not to do as someone with DVT?

There are several dietary restrictions and lifestyle modifications that patients should consider:

  • Reducing sitting still for long periods of time
  • Crossing legs while sitting
  • Increased daily movement
  •  Smoking
  •  Drinking alcohol
  • Wear compression socks


  1. Waheed SM, Kudaravalli P, Hotwagner DT. Deep Vein Thrombosis [Internet]. PubMed. Treasure Island (FL): StatPearls Publishing; 2023. Available from:
  2. Heestermans M, Poenou G, Hamzeh-Cognasse H, Cognasse F, Bertoletti L. Anticoagulants: A Short History, Their Mechanism of Action, Pharmacology, and Indications. Cells [Internet]. 2022 Oct 13;11(20):3214. Available from:
  3. Bhatt M, Braun C, Patel P, Patel P, Begum H, Wiercioch W, et al. Diagnosis of deep vein thrombosis of the lower extremity: a systematic review and meta-analysis of test accuracy. Blood Advances [Internet]. 2020 Apr 14;4(7):1250–64. Available from:
  4. Thompson AE. Deep Vein Thrombosis. JAMA [Internet]. 2015 May 26;313(20):2090. Available from:,injury%20can%20lead%20to%20DVT
  5. Umerah C o, Momodu II. Anticoagulation [Internet]. PubMed. Treasure Island (FL): StatPearls Publishing; 2023. Available from:
  6. Bartholomew JR. Update on the management of venous thromboembolism. Cleveland Clinic Journal of Medicine [Internet]. 2017 Dec [cited 2020];84(12 suppl 3):39–46. Available from:
  7. El-Rasheedy MI, Mohammed AH, Mahmoud AM. Clinical audit of anticoagulant therapy with pregnancy. Al-Azhar Assiut Medical Journal [Internet]. 2020 Sep;18(3):363–9. Available from:
  8. Mosarla RC, Vaduganathan M, Qamar A, Moslehi J, Piazza G, Giugliano RP. Anticoagulation Strategies in Patients With Cancer. Journal of the American College of Cardiology [Internet]. 2019 Mar 26;73(11):1336–49. Available from:
  9. Mazzolai L, Ageno W, Alatri A, Bauersachs R, Becattini C, Brodmann M, et al. Second consensus document on diagnosis and management of acute deep vein thrombosis: updated document elaborated by the ESC Working Group on aorta and peripheral vascular diseases and the ESC Working Group on pulmonary circulation and right ventricular function. European Journal of Preventive Cardiology [Internet]. 2021 Jul 13;29(8):1248–63. Available from:

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Simron Jakhu

Bachelor of Science - BSc (Hons) Biomedical Science, University of Wolverhampton

Simron is a first-class biomedical science graduate. She has experience in different areas such as data analysis, laboratory work, and academic writing. Her research project investigated the quantification of immunosuppressive proteins in glioblastoma multiforme by ELISA.

She is someone who enjoys learning and expanding her knowledge, especially in the areas of health and science. By using her experience and knowledge to write articles, Simron hopes they can be helpful to the general public. presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
Klarity is a citizen-centric health data management platform that enables citizens to securely access, control and share their own health data. Klarity Health Library aims to provide clear and evidence-based health and wellness related informative articles. 
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