17896 Factor V Leiden

Overview

Factor V Leiden is a genetic change (mutation) that makes your blood more likely to form clots than usual. It is not a disease by itself, but it increases your chances of developing a blood clot inside a vein, most often in your leg or lungs.

Yes, it is the most common inherited blood-clotting disorder. In the UK, about 1 in 20 people carry the mutated gene, but most of them will never have a clot.

It affects both men and women at birth, and it is found in all ethnic groups, though it is most frequent in people of European descent. Women face extra risk during pregnancy or when taking combined hormonal contraception.

Symptoms

Common symptoms

• No symptoms at all until a blood clot occurs
• Deep vein thrombosis (DVT): swelling, pain, warmth, and redness in one leg
• Pulmonary embolism (PE): sudden shortness of breath, chest pain, coughing up blood, and a fast heartbeat

Symptoms in children

• Children rarely develop clots, and if they do it is usually because they have another risk factor such as a long stay in hospital, a serious illness, or a central line (a tube in a vein). The symptoms are the same as in adults – leg swelling, pain, and breathing problems.

Symptoms in older adults

• Older adults have a higher risk of clots because of age, reduced mobility, and other health conditions. Symptoms are the same, but they might be mistaken for other problems, so it is important to get any new leg or breathing symptoms checked.

Causes

Main causes

• A change (mutation) in the factor V gene, which helps your body's blood-clotting system
• Inheriting the mutated gene from one or both parents – having one copy is enough to raise your risk, and two copies raises it further

Risk factors

• Family history of Factor V Leiden or blood clots
• Surgery, especially hip or knee replacement
• Long periods of immobility, such as bed rest or a long flight
• Pregnancy and the six weeks after giving birth
• Using combined oral contraceptives (the pill) or hormone replacement therapy
• Obesity, smoking, and increasing age

When to see a doctor

See a doctor urgently if:

• Go to your GP surgery or a walk-in clinic the same day if you have swelling, pain, or warmth in one leg, especially if you know you carry Factor V Leiden or have a family history of clots.

Book a routine appointment if:

• Make a routine appointment to discuss testing if you have a close relative with Factor V Leiden or if you are planning pregnancy or surgery and want to know your risk.

Diagnosis

A doctor can diagnose Factor V Leiden with a blood test that looks for the specific genetic change. It is usually requested after an unexplained blood clot, or if you have a strong family history of clots.

Tests that may be done

• Blood test for the factor V Leiden gene
• Sometimes a test for activated protein C resistance is done first, which can suggest the genetic change is present
• If you have had a clot, you may also have an ultrasound of the leg or a CT scan of the chest

What to expect at your appointment

The test is a simple blood draw from your arm. Results can take 1 to 3 weeks. You may be offered a discussion with a doctor or genetic counselor to help you understand what the result means for you and your family.

Treatment

There is no way to change the gene itself. Treatment focuses on preventing blood clots and managing any clot you might already have. Many people with Factor V Leiden do not need daily medication.

Self-care at home

• Stay active and avoid sitting for more than two or three hours at a time, especially on long journeys
• Keep well hydrated and avoid excess alcohol
• If your doctor prescribes compression stockings, wear them as advised
• Quit smoking and maintain a healthy weight

Medical treatments

If you have had a blood clot, your doctor may recommend a course of anticoagulant medicine – often called a blood thinner. These medicines make your blood less likely to clot, and they are usually taken for several months or longer. You may also be offered temporary anticoagulation before surgery, during pregnancy, or during long hospital stays, if your risk is high. Always follow your doctor's plan; never stop treatment without discussion.

When is surgery considered?

If you are having surgery, tell your surgeon and anaesthetist that you have Factor V Leiden. They may give you a temporary blood thinner before and after the operation, or use mechanical devices like compression boots, to lower your risk of a clot.

Living with this condition

Living with Factor V Leiden means being aware of your risk without letting it rule your life. Learn the signs of a blood clot, keep moving whenever you can, and let your doctor know about your condition before any procedure or pregnancy.

Lifestyle tips

• Take regular walks or do light exercise to keep blood flowing
• Move your legs and ankles during long trips – stand up, stretch, or flex your calf muscles
• Maintain a healthy weight to reduce extra pressure on your veins
• Wear medical compression stockings if recommended by your doctor

Diet and exercise

No special diet is required for Factor V Leiden itself, but a heart-healthy diet and regular exercise are good for your blood vessels and overall health. Avoid smoking, as it makes blood more likely to clot.

Mental health and emotional wellbeing

It is natural to feel anxious after learning you carry a genetic risk factor. You may worry about every ache or flight. This is understandable, but remember that the risk of an actual clot is still small for most people. If anxiety is affecting your sleep or daily life, talk to your doctor or a mental health professional.

Prevention

The gene itself cannot be changed, but blood clots caused by Factor V Leiden can often be prevented. This means staying active, managing body weight, and receiving temporary blood thinners during high-risk times like surgery, hospital stays, or pregnancy.

Screening programmes

Screening of family members may be considered if there is a strong history of clots. If you are a first-degree relative (child, sibling, or parent) of a known case, ask your doctor whether testing is useful for you. Not everyone needs testing, and it is always your choice.

Complications

If left untreated

• If a deep vein clot is not treated, it can travel to the lungs and cause a pulmonary embolism, which is a medical emergency
• Long-term leg damage (post-thrombotic syndrome) with pain, swelling, and skin changes
• A clot in an unusual place, such as the liver, brain, or placenta, can cause serious problems

Long-term outlook

The outlook is very positive. Most people with Factor V Leiden never have a blood clot, and even if you do, modern treatment is highly effective. With good communication with your doctor, a few sensible precautions, and early attention to warning signs, you can lead a long, active, and healthy life.

Find support

External links open third-party websites. Ruqelo Health is not responsible for external content. Listing an organisation does not imply endorsement.