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Frequently Asked Questions

Whether you are recently diagnosed, worried you have Thrombosis or are wanting to understand more, Thrombosis UK have compiled a list of questions and answers to the most commonly asked questions below:

PLEASE NOTE: For specific information about yourself, please speak to your GP or consultant.

What is a Deep Vein Thrombosis (DVT) blood clot ?

Within our blood there is a system known as the clotting mechanism that performs two vital, but opposite functions - the first to keep the blood flowing, with the second to form a 'plug' or clot to stop us from bleeding.

This clotting mechanism is highly effective and under normal circumstances it remains inactive. When we injure ourselves - a cut to the skin for example - the second function is activated and a clot is formed to protect us from the loss of blood. But sometimes this function can go wrong and the blood becomes a solid mass within a blood vessel that has not been cut, causing what is known as a thrombosis or clot.

A deep vein thrombosis or DVT is a blood clot forming in the veins deep in the leg, usually in the calf or thigh, although occasionally DVT can occur in other veins in your body. DVT blood clots can block the flow of blood partially or completely and this causes the symptoms of DVT.

What is a pulmonary embolism (PE) ?

An embolism is when a part of the clot 'breaks off' and travels around the body eventually blocking an artery. An example of this is a pulmonary embolism when part of the clot from a deep vein thrombosis breaks off, moves up the leg, through the heart and lodges in a lung artery or pulmonary artery. This process is known as embolisation, and the piece of clot is called an embolus.

Is a DVT the same as a varicose vein ?

A DVT is different from a varicose vein. A DVT is a more serious problem. Varicose veins form in the superficial veins just under the skin and are caused by the superficial veins not working as well as they could. These veins are not very important as they only transport blood from the skin and from the tissue just below the skin. A DVT forms in the deep veins in your legs. These veins are much more important as they transport most of the blood back to your heart. DVT blood clots can block the flow of blood in your leg veins, which can cause swelling and pain in the leg.

Is venous thrombosis common ?

Yes, venous thrombosis is known to occur in about one in every 1,000 of the population each year in the UK. But recent figures suggest that each year over 25,000 people in England die from venous thromboembolism (VTE) contracted in hospital. This is more than the combined total of deaths from breast cancer, AIDS and traffic accidents, and more than twenty-five times the number who die from MRSA. The figures are alarmingly high.

What are the symptoms of having a blood clot?

A DVT can be asymptomatic, but may be accompanied by some or all of the following symptoms: Pain, tenderness and swelling of the leg (usually the calf), sometimes accompanied by discolouration with the leg appearing a pale, blue or reddish purple colour. If thrombosis occurs in the thigh veins, the whole leg may be swollen.

The symptoms of pulmonary embolism can include: shortness of breath, either severe and sudden or gradual onset; chest pain may be worse on inhalation; sudden collapse; and the symptoms of deep vein thrombosis may also be present.

What are the complications of a DVT?

In addition to the serious risk of an embolus, the consequences of DVT include post-phlebitic syndrome. Normally the valves in deep veins prevent blood from travelling back down the leg. Damage to these valves higher in the leg can cause increased pressure in the veins of the lower calf and ankle and cause swelling, pigmentation skin rashes and varicose ulcers. This is known as post-phlebitic syndrome.

What are the complications of a pulmonary embolus (PE)?

It is important to realise that a PE is a medical emergency. Although most cases can be diagnosed quickly and effectively treated, in some cases, death can occur quickly. Guidelines for doctors recommend that patients waiting for a test to confirm the diagnosis of PE should be given treatment even before the diagnosis is confirmed because of the risk of death.

A PE is regarded as a serious condition because of other severe complications, including strain on the right ventricle of your heart (ventricular failure) and hypertension. A serious, long-term complication called chronic thromboembolic pulmonary hypertension, when most of the arteries in the lung get blocked with blood clots, occurs in around 1 in 25 patients with a PE after two years.

How is thrombosis treated?

If you have been diagnosed with thrombosis, it is very important to be treated immediately. Normally, DVT is first treated with two drugs - an injection of an anticoagulant called heparin and a blood thinner called warfarin, taken as a tablet. Warfarin takes several days to work and so injections of heparin are given for up to 5 days to thin the blood immediately. After 5 days treatment with both drugs, warfarin is continued, usually for no longer than 6 months. These drugs stop blood clots from forming, so you should be aware that if you cut yourself, it will take more time for the wound to heal.

Compression stockings (also called graduated compression stockings) can also be used, and are sometimes given to relieve pain, swelling and to prevent post thrombotic syndrome. These will be fitted by your doctor and cannot be bought over the counter at the pharmacy. Your doctor may ask you to wear stockings for an extended period after a DVT.

Can I prevent a thrombosis happening?

Of course it is much better to prevent a DVT before it happens than have to treat a DVT. Preventing DVT is an important consideration for your doctor, most especially if you are admitted to hospital. You can help prevent DVT by staying mobile, if this is possible. If you are undergoing surgery, or are going into hospital for an extended period because you are ill, you are at greater risk of DVT, and doctors will give you stockings to wear and may give you an anticoagulant drug.

Am I at risk of DVT?

Large studies have shown clearly that certain people are more likely to get thrombosis than others. For example, older people are more likely to have a DVT than a younger person, particularly if the older person is immobile or has a serious illness such as cancer. Any illness or injury that causes immobility increases the thrombosis risk. A recent operation is a common factor in people with DVT.

If you have had a DVT before, you are more likely to suffer another clot. Pregnancy increases the risk of thrombosis, with about 1 in 1000 pregnant women likely to have DVT. Cancer markedly increases the risk of having a DVT, as does a medical illness which is severe, such as heart failure or respiratory disease. Hormone-based treatment, such as the contraceptive pill and hormone replacement therapy can cause the blood to clot more easily. Obesity increases the risk of having a DVT.

I have had a DVT, should I be tested for an underlying cause?

DVT and PE can be divided into 'provoked' or 'unprovoked'. Provoked means that there is a clear factor causing the clot, the usual one is hospital admission, we call these hospital acquired thrombosis (HAT). The risk of having another clot is very low so we treat these for three months and there is no need to look for any other causeIf there is no reasonable identifiable cause for the clot, what we call unprovoked or you have a second clot then there is a risk of recurrent clot especially in men.

The NICE guidelines recommend continued use of oral anticoagulants (blood thinners, such as warfarin, apixaban, rivaroxaban, edoxaban or dabigatran) If there is uncertainty to the benefit of continuing the anticoagulation then antiphospholipid testing should be requested. If the patient has a strong family history (i.e DVT and or PE in close family members) then inherited thrombophilia test should be performed.

What is thrombophilia testing?

Thrombophilia tests are looking for underlying sticky blood that predisposed to DVT and PE (not to heart attack and stroke). They can he inherited – present in the genes or acquired- develop during adult life.

Who should perform a thrombophilia screen?

Someone who understands the results! So an expert in thrombosis- most of them are consultant Haematologists.

When is the best time to have thrombophilia tests done?

Ideally when you are not anticoagulated, because anticoagulants interfere with the results. A few can be performed on anticoagulation.

What are the main thrombophilias?

There are two main types of thrombophilia and they are inherited and acquired. The inherited thrombophilia vary enormously in their stickiness and presence in the population.

The common thrombophilias are heterozygous Factor V Leiden (which affects 5% of the white population)and Prothombin 20210 (affects 2% of the white population), they both have a very mild effect on increasing blood stickiness, indeed most people with Factor V Leiden never have a clot!

The rarer ones are Protein C deficiency, Protein S deficiency and antithrombin deficiency affecting about one in 5,000 of the population and cause much sticker blood than the common ones.

Homozygous Factor V Leiden affects 1 in 1600.

Finally there is dysfibrinogenaemia, very rare indeed, affecting one in a million of the population.

Acquired thrombophilias included a number of rare conditions, the commonest is are antiphospholipid syndrome (APS, also known as Hughes Syndrome after Prof Hughes who described it).

If I have an inherited thrombophilia should my family members be tested?

We no longer test family members for the common thrombophilias such as Factor V Leiden or prothrombin 201201 because they are so very low risk and testing positive might result in more anxiety than benefit.

In those with a rare thrombophilia, it might be helpful to test the children when they reach puberty, so they are aware of their sticky blood and protection can be offered to prevent clots at time of risk of clot e.g. operations, advised not to smoke, to stay slim and get regular exercise and not to use the combined oral contraceptive pill.

Doctors are very disappointed with inherited thrombophilia testing because no one has looked at the non white populations to see what if any thrombophilias might be present. For example Factor V Leiden is only present in the white population so a waste of time testing for in the non white population. Furthermore in 2016 we don't know enough about clotting to identify all the inherited problems. If we had 100 white people who had DVT/PE and had a very strong family history of clots, we would only identify an underlying inherited thrombophilia in 50%, yet the other 50% clearly have an inherited problem but we don't have the tests to identify it.

If I have antiphospholipid antibodies should my family members be tested?

We don't normally do this, because familial antiphospholipid syndrome is very rare.

If I have one episode of VTE and I have a thrombophilia will I need to be anticoagulated long term?

This will depend on which thrombophilia, for example with Factor V Leiden.

You don't have a greater risk of having another clot and therefore we don't normally continue long term anticoagulation unless other risk factors e.g. obesity and/or continued immobility are present. However those with a high risk of recurrent clot such as antithrombin deficiency and the clot was unprovoked, anticoagulation will be continued.

Are there any psychological effects of blood clots?

For some patients the experience and subsequent diagnosis of a blood clot can be distressing and its severity may range from very mild to overwhelming.

For some patients the symptoms of blood clots may be unpleasant and upsetting. A clot on the lung which causes chest pain and or breathlessness can be very upsetting and it is common for people to worry that it might happen again.

Other patients, even if they have mild symptoms, may become worried because they are aware that clots can sometime be fatal. Anyone who has experienced a potentially fatal event may become anxious about it happening again.

Some patients can develop a more extreme anxiety condition which is similar to post traumatic stress disorder. This is often associated with a chronic feeling of anxiety, increased vigilance for symptoms of clot recurrence and even disturbing 'flashbacks' to their diagnosis.

It is important to recognize that it is normal to worry after any period of illness. However, the ability to talk to someone about the clot can often minimize the long term psychological impact. Some people who have severe psychological effects may benefit from talking to a counselor or clinical psychologist.

Watch our Video - Psychological Effect of Thrombosis

It is my first DVT/PE how long will I be on anticoagulation for?

Usually is 3 months in the first instance as advised by the NICE guidelines. If it is a straightforward provoked clot then treatment can be stopped at this stage.

Can I form fresh clots whilst on anticoagulation?

Although extremely unlikely this very occasionally occurs. If you feel like you maybe have another clot you must seek medical advice immediately.

Do anticoagulants dissolve blood clots?

No, anticoagulants do not dissolve blood clots, they prevent new clots forming.

What anticoagulants are available?

Warfarin and heparin have been available for 50 years but now a new generation of blood thinners have been licensed. These include apixaban, dabigatran, edoxaban, and rivaroxaban. All are suitable for treating DVT/PE.

I've been told to avoid vitamin K whilst on warfarin is this true?

Warfarin is what is known as a vitamin K antagonist so increased and decreased intake of vitamin K will alter blood thinness (this is known as the INR levels). The key to good INR control is to eat approximately the same amount of vitamin K daily. In the average British diet vitamin K comes from green vegetables and cauliflower, so approximately eat the same amount daily.

Some other patients inject low molecular weight heparins such as Fragmin and Clexane if their INR dips below a certain level should I do this also?

This is dependent on what your consultant or GP recommends. There is currently no guidance that recommends patients on warfarin do this and will depend on particular circumstances.

I feel nervous about stopping anticoagulation suddenly because my three months treatment is over can I stay on it?

Anticoagulants are excellent treatment for VTE but are do not come without risk.. If there is no medical reason such as further clots for you being on it there is no reason why you should remain. Thousands of people stop anticoagulation and go on to have no further episodes of clots.

Can I shave, have my eyebrows/legs waxed/plucked whilst on anticoagulation?

Yes you can.

What is post thrombotic syndrome?

Post thrombotic syndrome is when the damage to the leg veins from a DVT causes ongoing symptoms such as pain, swelling, redness, itching, ulcers.

What are the physical symptoms of post thrombotic syndrome (PTS)?

The symptoms of PTS can range from mild to moderate aching in the affected limb to in very serious cases ulceration of the inner ankle. The most common symptoms are swelling, pain (aching or cramping), venous eczema (skin rash), itching, varicose veins, discolouration of the skin, hardening of the skin and, limited mobility(through swelling).

We know PTS can affect quality of life i.e it be debilitating. Up to 30% of people who have had a DVT may develop symptoms within the first five years. However most people will develop symptoms within the first 6 months to two years.

How do you tell the difference between PTS and a fresh DVT?

This is something that most patients develop with increased body awareness over time. The general rule most patients follow is if in doubt that there might be a fresh DVT then always get it checked out.

Are there any treatments for PTS?

There is research currently ongoing into treating post PTS, mainly at St Thomas' where new stenting techniques are being used. However they are not suitable for everyone yet and we don't know their long term effects. If you are suffering from PTS, a referral to a vascular surgeon is to assess whether you are suitable for any surgical treatment. The treatment is changing fast, so what this space!

My post thrombotic syndrome is really bad can I claim disability benefit?

This is a very common question and yes PIP/DLA is awarded for mobility issues due to PTS. Whether or not you get awarded is really down to the severity of your symptoms. It is always worth seeking professional advice when completing these forms in order to give yourself the best chance.

Developed for the NHS, the VTE self-assessment tool provides a useful tool to help you see whether you may be at risk of a DVT whilst in hospital and give you the relevant information to take with you to show your doctor.


content provided by NHS Choices

Thrombosis can happen to anyone you, your family, your friends or colleagues. Thrombosis is often a silent medical condition with no obvious signs or symptoms. It doesn't discriminate and can affect people of any age or sex. It can very easily be confused with less serious conditions a clot in the leg can be mistaken for a sore leg muscle.