Deep vein thrombosis (DVT)

What is deep vein thrombosis?

eep vein thrombosis (DVT) is when a blood clot (thrombus) forms in one of the deep veins in your body, usually the leg. The deep veins in the legs supply the muscles of the calf and thighs, and are not the veins you can see below the skin. A blood clot can entirely or partially block blood flow in these veins. 

Sometimes the clot will break off, travel through your bloodstream and get stuck in your lungs causing a pulmonary embolism (PE). This is a life-threatening emergency, so call 999 and seek medical help immediately if you suspect PE. 

Although most DVT forms in the leg, it can also develop elsewhere in the body such as the arm, foot or ankle. It usually affects one leg but in rare cases can occur in both. 

What are the symptoms of deep vein thrombosis?

Symptoms of deep vein thrombosis in the leg include:

• Pain – throbbing in the calf, thigh or entire leg (it usually only affects one leg)

• Redness – particularly around the affected area, commonly at the back of your leg below the knee

• Warmth – skin feels warm in the area of the blood clot

• Swelling – swollen veins are tender to touch

Who is at risk of deep vein thrombosis?

Anyone can develop a deep vein thrombosis but there are several factors that can increase your risk:

• Age – your risk of developing DVT increases when you’re over 60 years of age

• Being overweight or obese

• Smoking 

• A personal history of deep vein thrombosis or pulmonary embolism

• A family history of blood clots

• Being immobile – for example after an operation or staying in bed for a long period of time

• Pregnancy – your blood clots more easily during pregnancy or in the first 6 weeks after having a baby

• Hormones – taking the combined contraceptive pill or hormone replacement therapy (HRT) which both contain oestrogen increases your risk

• Existing conditions or treatments that cause your blood to clot more easily – thrombophilia (blood clotting disorder), cancer especially when treated with chemotherapy and radiotherapy, and heart and lung disease

How is deep vein thrombosis diagnosed?

Deep vein thrombosis is diagnosed by a doctor using a combination of your symptoms, medical history, examination findings, blood tests and scans. 

If a GP suspects that you have DVT, you should be referred to the hospital for an ultrasound scan within 24 hours. An ultrasound scan will assess for blood flow through veins in the legs and can identify blockages. You may also have a venogram (X-ray of the vein) which can show the exact location of the blood clot.

If pulmonary embolism is suspected, you may undergo additional tests to assess the blood flow in the blood vessels in your lungs.

How to treat deep vein thrombosis

If there’s a high level of suspicion, you might be put on injections to thin your blood while waiting for a scan. 

Once a DVT is confirmed, then the usual treatment is with anticoagulant tablets (commonly rivaroxaban or warfarin). Anticoagulants prevent blood from sticking together and can dissolve existing blood clots. 

If you have DVT during pregnancy, you are treated with anticoagulant injections for the remainder of the pregnancy and until your baby is 6 weeks old. 

How to prevent deep vein thrombosis

Simple lifestyle measures will help reduce your risk of developing DVT:

• Maintaining a healthy weight

• Staying active

• Drinking plenty of fluids to avoid dehydration (which makes your blood more likely to clot)

• Cutting down on smoking and alcohol consumption

If you’re going to sit still on a long journey, you may find compression socks (available in pharmacies) helpful to prevent blood clots. 

When should I seek help?

If you’re experiencing the symptoms of deep vein thrombosis, you should seek prompt medical advice from a GP.

Call 999 or go to A&E if you have the symptoms of DVT and:

• Acute chest pain

• Acute difficulty breathing