If you have deep vein thrombosis (DVT), you'll need to take a medicine called an anticoagulant.

Anticoagulation

Anticoagulant medicines prevent blood clots getting bigger. They can also help stop part of the blood clot breaking off and becoming lodged in another part of your bloodstream (an embolism).

Although they're often referred to as "blood-thinning" medicines, anticoagulants don't actually thin the blood. They alter proteins within it, which prevents clots forming so easily.

Heparin and warfarin are two types of anticoagulants that are used to treat DVT. Heparin is usually prescribed first because it works immediately to prevent further clotting. After this initial treatment, you may also need to take warfarin to prevent another blood clot forming.

Heparin

Heparin is available in two different forms:

  • standard (unfractioned) heparin
  • low molecular weight heparin (LMWH)

Standard (unfractioned) heparin can be given as:

  • an intravenous injection – an injection straight into one of your veins
  • an intravenous infusion – where a continuous drip of heparin (via a pump) is fed through a narrow tube into a vein in your arm (this must be done in hospital)
  • a subcutaneous injection – an injection under your skin

LMWH is usually given as a subcutaneous injection.

The dose of standard (unfractionated) heparin to treat a blood clot varies significantly from person to person, so the dosage must be carefully monitored and adjusted if necessary. You may need to stay in hospital for 5 to 10 days and have frequent blood tests to ensure you receive the right dose.

LMWH works differently from standard heparin. It contains small molecules, which means its effects are more reliable and you won't have to stay in hospital and be monitored.

Both standard heparin and LMWH can cause side effects, including:

  • a skin rash and other allergic reactions
  • bleeding 
  • weakening of the bones if taken for a long time (although rare with LMWH)

In rare cases, heparin can also cause an extreme reaction that makes existing blood clots worse and causes new clots to develop. This reaction, and weakening of your bones, is less likely to occur when taking LMWH.

In most cases, you'll be given LMWH because it's easier to use and causes fewer side effects.

Warfarin

Warfarin is taken as a tablet. You may need to take it after initial treatment with heparin to prevent further blood clots occurring. Your doctor may recommend that you take warfarin for three to six months. In some cases, it may need to be taken for longer, even for life.

As with standard heparin, the effects of warfarin vary from person to person. You'll need to be closely monitored by having frequent blood tests to ensure you're taking the right dosage.

When you first start taking warfarin, you may need to have two to three blood tests a week until your regular dose is decided. After this, you should only need to have a blood test every four weeks at an anticoagulant outpatient clinic.

Warfarin can be affected by your diet, any other medicines you're taking, and by how well your liver is working.

If you're taking warfarin you should:

  • keep your diet consistent
  • limit the amount of alcohol you drink (no more than 14 units of alcohol a week)
  • take your dose of warfarin at the same time every day
  • not start to take any other medicine without checking with your GP, pharmacist or anticoagulant specialist
  • not take herbal medicines

Warfarin isn't recommended for pregnant women who are given heparin injections for the full length of treatment.

Rivaroxaban

Rivaroxaban is a medication recommended by the National Institute for Health and Care Excellence (NICE) as a possible treatment for adults with DVT, or to help prevent recurrent DVT and pulmonary embolism.

Rivaroxaban comes in tablet form. It's a type of anticoagulant known as a directly acting oral anticoagulant (DOAC). It prevents blood clots forming by inhibiting a substance called factor Xa and restricting the formation of thrombin (an enzyme that helps blood clot).

Treatment usually lasts three months and involves taking rivaroxaban twice a day for the first 21 days and then once a day until the end of the course.

Read the NICE guidance about rivaroxaban for the treatment and prevention of recurrent deep vein thrombosis and pulmonary embolism.

Apixaban

NICE also recommends apixaban as a possible method of treatment and prevention for DVT and pulmonary embolism.

Like rivaroxaban, apixaban is a DOAC that's taken orally as a tablet, and prevents blood clots forming by hindering factor Xa and restricting the formation of thrombin.

Treatment usually lasts at least three months and involves taking apixaban twice a day.

Read the NICE guidance about apixaban for the treatment and secondary prevention of deep vein thrombosis and pulmonary embolism.

Compression stockings

Wearing compression stockings helps prevent calf pain and swelling, and lowers the risk of ulcers developing after having DVT.

They can also help prevent post-thrombotic syndrome. This is damage to leg tissue caused by the increase in venous pressure that occurs when a vein is blocked by a clot and blood is diverted to the outer veins.

After having DVT, stockings should be worn every day for at least two years. This is because symptoms of post-thrombotic syndrome may develop several months or even years after having a DVT.

Compression stockings should be fitted professionally and your prescription should be reviewed every three to six months. The stockings need to be worn all day but can be taken off before going to bed or in the evening while you rest with your leg raised (see below). A spare pair of compression stockings should also be provided.

Exercise

Your healthcare team will usually advise you to walk regularly once compression stockings have been prescribed. This can help prevent symptoms of DVT returning and may help to improve or prevent complications of DVT, such as post-thrombotic syndrome.

Raising your leg

As well as wearing compression stockings, you might be advised to raise your leg whenever you're resting. This helps to relieve the pressure in the veins of the calf and stops blood and fluid pooling in the calf itself.

When raising your leg, make sure your foot is higher than your hip. This will help the returning blood flow from your calf. Putting a cushion underneath your leg while you're lying down should help raise your leg above the level of your hip.

You can also slightly raise the end of your bed to ensure that your foot and calf are slightly higher than your hip.

Read more about preventing DVT.

Inferior vena cava filters

Although anticoagulant medicines and compression stockings are usually the only treatments needed for DVT, inferior vena cava (IVC) filters may be used as an alternative. This is usually because anticoagulant treatment needs to be stopped, isn't suitable, or isn't working.

IVC filters are small mesh devices that can be placed in a vein. They trap large fragments of a blood clot and stop it travelling to the heart and lungs. They can be used to help prevent blood clots developing in the legs of people diagnosed with:

  • DVT
  • pulmonary embolism
  • multiple severe injuries

IVCs can be placed in the vein permanently, or newer types of filters can be placed temporarily and removed after the risk of a blood clot has decreased.

The procedure to insert an IVC filter is carried out using a local anaesthetic (where you're awake but the area is numb). A small cut is made in the skin and a catheter (thin, flexible tube) is inserted into a vein in the neck or groin area. The catheter is guided using an ultrasound scan. The IVC filter is then inserted through the catheter and into the vein.

Page last reviewed: 27/04/2016

Next review due: 01/04/2019