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Hospital Acquired Thrombosis (HAT)

Any patient admitted to hospital is potentially at risk of developing a Deep Vein Thrombosis (DVT). This leaflet will explain what a DVT is, who is most at risk of getting one and what you can do to help reduce your risk. It will also tell you what symptoms might suggest the presence of a DVT and what you should do if you experience any of them. 

A contact telephone number and details of how to obtain further information are given at the end of the leaflet.

What is a DVT?
A DVT is a blood clot which forms in a deep vein, usually in the leg. Deep veins are large veins which transport blood to the heart. When a blood clot occurs, it forms a plug that can interrupt this blood flow.

Is a DVT serious?
A DVT may cause pain and swelling in the leg, which usually resolves with treatment. However, in some cases problems may develop as a result of poor blood flow through the legs such as pain, swelling and ulcers of the lower leg. 

In many cases, the initial DVT is ‘silent’ and does not cause any symptoms in the leg, causing problems only when a portion of the blood clot breaks off and travels through the blood stream and becomes lodged in the lungs. This is known as a Pulmonary Embolism (PE).

A PE usually causes chest pain, shortness of breath and coughing, sometimes with bloody phlegm, and sudden collapse.

In rare cases, a PE is fatal, and if you develop any of the above symptoms you should seek immediate medical attention.

Are you at risk of DVT?     
Many people think that going on a long aeroplane flight is a big risk factor for DVT development. Unfortunately the risk of developing a DVT following admission to hospital is far greater. 

Can a DVT be prevented?
The good news is that the development of a DVT following an admission to hospital can be prevented in the majority of cases with safe and effective treatments. If any of the following risk factors apply to you, you should discuss DVT prevention with your doctor. You will then be assessed as to whether any treatments should be given in your particular case.

Risk factors for developing a DVT

  • You are immobile
  • You are over 60 years of age 
  • You have cancer or are receiving treatment for cancer 
  • You are taking hormone replacement therapy or a contraceptive that contains oestrogen
  • You are pregnant or have had a baby in the past 6 weeks
  • You are overweight 
  • You are going on a long-distance flight (more than 6 hours) following discharge from hospital
  • You have had a previous DVT or PE
  • You have a family history of DVT or PE
  • You have had surgery in the past 3 months

Your right to a DVT risk assessment
The Department of Health recommends that all adults who are admitted to hospital should be assessed for their risk of developing a DVT. If it is felt that the risk is increased then appropriate treatments should be prescribed. 

At Velindre, the treatment most commonly prescribed is one called dalteparin. 

What is Dalteparin?
Dalteparin is a blood thinning injection which helps prevent the formation of a DVT. It is a single, once daily, subcutaneous injection (which means it is injected beneath the skin). It is usually injected into a skin fold in your abdomen (stomach), or the upper part of your thigh.

Its main side effect is bruising at the site of injection.       

Discharge from hospital
The risk of developing a blood clot may persist for several months following discharge form hospital. It is important that you follow advice given to you upon discharge from hospital to reduce the risk of DVT occurring at a later stage. 
If you develop any symptoms that suggest you might have a DVT or PE, please seek immediate medical attention. 

Contact telephone numbers
If you would like any more information about dalteparin please speak to your doctor or pharmacist.
Pharmacy department - 029 2061 5888 ext 6223
Monday – Friday 9am – 5pm for queries about your medicines

Additional information can be obtained from Lifeblood the Thrombosis charity at 

This leaflet was written by health professionals.  The information contained in this leaflet is evidence based.  It has been approved by doctors, nurses and patients.