Deep vein thrombosis | DVT or poketoto

Blood clots

Deep vein thrombosis (DVT or poketoto) occurs when a blood clot forms in a vein in your body, usually in your legs.

Veins are blood vessels that carry blood from the tissues of the body back to your heart. A DVT (deep vein thrombosis) is a blood clot that occurs in the deep veins. The most common veins to be affected are those in your legs.

A DVT can block blood flow to important areas of your body such as your lungs, heart or brain and this can be dangerous. Pulmonary embolism (a blood clot in the lung) is the most common of these serious DVT complications. 

Credits: Deep vein thrombosis, NHS

What are the symptoms of DVT?

A DVT can occur in any limb but tends to occur more commonly in the leg – involving the foot, ankle, calf or whole leg.

Signs and symptoms can include:

  • Swelling in the affected limb. Rarely, there may be swelling in both legs.
  • Pain in your leg. The pain often starts in your calf and can feel like cramping or a soreness.
  • Change of colour in the leg – bluish, purple or reddish skin colour.
  • Feeling of warmth on the skin of the painful or swollen area.   

These symptoms may often be confused with a sprained ankle or other injury. DVT may sometimes occur without any noticeable symptoms. If you develop signs or symptoms of DVT, contact your doctor urgently.

Seek immediate medical help if:

You have symptoms of DVT, such as pain and swelling, and:

• breathlessness
• chest pain.

These symptoms could mean you have a pulmonary embolism. A pulmonary embolism can be life threatening and needs treatment straight away.

Call Healthline on 0800 611 116 if you are unsure about what to do.

Who is at risk of developing DVT?

Many factors can increase your risk of developing DVT. The more risk factors you have, the greater your risk.

A DVT is more likely to happen if you:

  • are over 60 years of age
  • are overweight
  • smoke
  • have had a DVT before
  • take the contraceptive pill or HRT
  • have cancer or heart failure
  • have varicose veins.

There are also some temporary situations when you're at more risk of DVT. These include if you:

  • are staying in or recently left hospital – especially if you cannot move around much (like after an operation)
  • are confined to bed
  • go on a long journey (more than 3 hours) by plane, car or train
  • are pregnant or if you've had a baby in the previous 6 weeks
  • are dehydrated.

How is DVT diagnosed?

If you suspect you have a DVT, even if you have mild symptoms, you must seek medical attention urgently. This can prevent serious complications such as a pulmonary embolism.

To diagnose DVT, your doctor will ask you questions about your symptoms. You may also have a physical exam to check for any areas of swelling, tenderness or discoloration on your skin.

Your doctor may suggest further testing, including an ultrasound scan. The scan can show whether blood is flowing normally through your vein. Your doctor will also do a blood test to check how well your blood is clotting.

How is DVT treated?

The main aim of DVT treatment is to prevent the clot from getting any bigger, and from breaking loose and causing a pulmonary embolism. After that, the goal becomes reducing your chances of deep vein thrombosis happening again. Treatment will depend on the location and severity of the clot. Treatment usually includes a combination of medicine and compression.

With treatment, the pain and swelling usually reduces within a few days of starting treatment.

Medicines – anticoagulants

Anticoagulants work by interrupting the clot-forming process. For the treatment of a DVT, anticoagulants can stop the existing clot from getting bigger.

Common examples of anticoagulant medicines are:

You may require regular blood tests to check how well the anticoagulants are working. Anticoagulant treatment usually continued for at least 3 months to be fully effective in treating a DVT. In some cases, it may be needed for a longer period.

DVT in pregnancy is treated differently and usually needs a longer treatment course. Your doctor will give you advice on the treatments available.

Compression stockings

These are special types of stockings that are made from special elastic to give support to the lower legs. They encourage circulation and help to reduce swelling. This pressure helps reduce the chances that your blood will pool and clot. These stockings are worn on your legs from your feet to about the level of your knees.

How can DVT be prevented? 

Although DVT cannot be prevented in all situations, there are a few things you can do to lower your risk:

  • Avoid sitting for long periods of time. Elevate your legs if you are sitting for moderate periods of time. 
  • Do not cross your legs when sitting. 
  • Get up and move around every hour or so.
  • If you are travelling on a long journey or are bedridden in hospital there are special precautions you can take. See travel-related DVT and hospital-related DVT.
  • If you smoke, quit smoking or reduce the amount that you smoke. The nicotine causes your blood vessels to become smaller which means the blood flow is decreased.
  • If you are overweight, aim to reduce weight. 
  • Exercise regularly. 
  • Keep hydrated – drink 6–8 glasses of water a day.

Learn more

Deep vein thrombosis Patient Info, UK
Deep vein thrombosis Southern Cross, NZ
Deep vein thrombosis in pregnancy Healthinfo, NZ


  1. Deep vein thrombosis (blood clots) Centres for Disease Control and Prevention (CDC), US, 2020
  2. DVT (Deep vein thrombosis) NHS, UK, 2019
Credits: Health Navigator Editorial Team. Reviewed By: Andrew McLachlan, Nurse Practitioner Cardiology, Counties Manukau DHB Last reviewed: 15 Sep 2016