Deep vein thrombosis (DVT): treatment, symptoms, causes and prevention

The NHS says DVT is treated with blood-thinning medicines (anticoagulants). You will usually need to take them, such as rivaroxaban, for at least 3 months to reduce your risk of getting another blood clot, and they are usually taken as tablets. NICE guidance likewise says anticoagulation treatment should be offered for at least 3 months to people with confirmed proximal DVT or pulmonary embolism, and that apixaban or rivaroxaban are the usual first choices.

If you get a DVT when you are pregnant, the NHS says you will usually need blood-thinning injections for the rest of your pregnancy and until your baby is 6 weeks old. You may also need other treatments if a condition has caused your DVT, and further tests if the cause is not clear.

NICE CKS adds that people with an unprovoked DVT, meaning one with no recent major risk factor, should be investigated for undiagnosed cancer and offered thrombophilia testing where appropriate, and that primary care addresses modifiable risk factors such as obesity.

The NHS lists the symptoms of a DVT in the leg as throbbing pain in 1 leg (rarely both), usually in the calf or thigh; swelling in 1 leg; red, blue or darkened skin around the painful area, which may be harder to see on brown or black skin; and swollen veins. Symptoms can sometimes happen in the arm if that is where the clot is.

The NHS notes that sometimes the only symptom is pain in the lower tummy, a symptom of pelvic vein thrombosis, which is rare. NICE CKS says symptoms are usually on one side and may be very subtle or even absent.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you think you have DVT. If you are pregnant you can also call an early pregnancy unit (less than 20 weeks) or your maternity unit.

Call 999 or go to A&E if you have symptoms of DVT such as pain and swelling and you feel short of breath or have chest pain, because blood clots can travel to the lungs. The NHS says a pulmonary embolism can be life-threatening and needs treatment straight away. Do not drive yourself to A&E; ask someone to drive you or call 999.

For pulmonary embolism itself, the NHS lists sudden difficulty breathing, chest pain that is worse when you breathe in, and coughing up blood, and says to call 999 for severe difficulty breathing, pain in the chest or upper back, a very fast heartbeat, or if someone has passed out.

NICE CKS defines DVT as the formation of a blood clot in a deep vein, usually in the legs, which partially or completely obstructs blood flow. It describes a provoked DVT as one in a person with a recent, transient major risk factor such as surgery, trauma, significant immobility or pregnancy, or someone on hormonal treatment, and an unprovoked DVT as one without such a factor.

NICE CKS gives an annual incidence of about 1 to 2 per 1000 people, and names pulmonary embolism as the most serious complication.

The NHS says DVT is more likely if you are aged over 60, are living with overweight or obesity, smoke, have had a DVT before, take HRT or the combined contraceptive pill or oestrogen-containing contraception, have cancer or heart failure, have varicose veins, have thrombophilia, or have inflammatory bowel disease or vasculitis.

There are also times when the chance is higher: during or soon after a hospital stay, especially if you cannot move around much; having or having had surgery; being confined to bed for 3 days or more; a long journey of more than 4 hours by plane, car or train; being pregnant or having had a baby in the previous 6 weeks; or being dehydrated.

The NHS says that if a doctor thinks you have DVT you should be referred to hospital within 24 hours for an ultrasound scan, which shows whether blood is flowing normally through the vein.

NICE explains that clinicians use a two-level DVT Wells score to estimate how likely a DVT is. If DVT is likely, a proximal leg vein ultrasound scan is offered with the result available within 4 hours if possible. If DVT is unlikely, a D-dimer blood test is offered. If the scan or test result cannot be obtained within 4 hours, interim anticoagulation is offered while waiting, with a scan within 24 hours. A negative D-dimer test means interim treatment is stopped and another diagnosis is considered.

The main danger the NHS highlights is pulmonary embolism, where part of the clot dislodges and travels to the lungs. It says that is why DVT can be very serious. If treated early, the NHS says people should make a full recovery from a pulmonary embolism.

Treatment of pulmonary embolism involves anticoagulant injections for at least 5 days, followed by anticoagulant tablets for at least 3 months, according to the NHS.

The NHS suggests staying a healthy weight, staying active, drinking plenty of fluids to avoid dehydration, not sitting still for long periods (get up and move around every hour or so), not smoking, and not drinking lots of alcohol.

On a journey of 4 hours or more, wear loose clothing, drink plenty of water, avoid alcohol and walk around when possible. In hospital, your healthcare team should check if your chance of DVT is higher, and may give you preventive medicine or compression stockings. NHS advice on flight socks is part of its pulmonary embolism guidance, and it recommends bending and straightening legs, feet and toes every 30 minutes while seated.

Note that NICE says not to offer elastic graduated compression stockings to prevent post-thrombotic syndrome or recurrence after a DVT, although they may be offered to manage leg symptoms.

A suspected DVT is assessed urgently. On the NHS, that means a GP appointment, NHS 111 or hospital referral, with a scan within the timescales above. Private hospitals can also arrange leg vein scans and anticoagulation, but the diagnostic approach and drugs are the same as in the NICE guidance.

Whichever route you use, make sure you know how long you are expected to take blood thinners, who will review them, and which symptoms of bleeding or a new clot should make you seek help.