For this reason, the NHS recommends requesting an urgent GP appointment or calling 111 if you have DVT symptoms, or going to A&E or calling 999 if you have chest pain or shortness of breath.
Who’s at risk?
The British Heart Foundation says about 60,000 UK adults are thought to develop DVT each year, and Thrombosis UK says one in 20 people will experience the condition in their lifetime. Between VTE and arterial blood clots (which can cause heart attacks and strokes), as many as one in four deaths are related to blood clots, making blood clots a leading cause of preventable hospital deaths.
Broadly speaking, your risk of a blood clot is determined by your age, genetics and your overall health. But even if there’s no family history of blood clots, experts say that the risk of VTE roughly doubles with each decade after the age of 40. It typically occurs when you’re over 60 as the levels of proteins that help blood clot increase with age, veins become less elastic, which impedes blood flow, and higher rates of hospitalisation and chronic illness limit mobility.
Being immobile, suffering a serious injury, undergoing medical procedures and taking certain medications are all known to increase a person’s risk of VTE, which is why Thrombosis UK notes that hospital stays are particularly associated with blood clots, with an elevated risk up to 90 days after you have been discharged.
Having cancer, as well as receiving treatment for cancer, increases your risk, and heart failure causes problems because of poor circulation and inflammation within the blood vessels. High blood-sugar levels that come with uncontrolled diabetes can damage the lining of blood vessels, which also encourages clotting.
During pregnancy, and for six weeks after giving birth, women become much more likely to develop DVT. This is why Thrombosis UK has introduced a screening tool to help newly pregnant women assess their risk and see whether they might need blood thinners.
What are the signs you have DVT?
The NHS flags five key symptoms:
Throbbing pain in one leg when walking or standingSwelling in one legWarm skin around the painful areaRed or darkened skin around the painful areaSore, swollen veins
Hunt warns, however, that not all of these signs may be present.
“You should pay attention to unexplained pain in the leg that doesn’t go away and doesn’t seem to be related to exercise or a pulled muscle,” she says. “Most people just have pain; 80 per cent have no swelling at all. If it progresses to a pulmonary embolism, you may start having unexplained chest symptoms, such as gradually becoming more short of breath, chest pain, especially when breathing in, and even coughing up blood.”
How to prevent DVT
Hunt says there is no “magic” way to prevent DVT, but a few simple lifestyle changes can significantly reduce your risk.
Maintain a healthy weight
“As a rule, the higher your BMI, the greater your risk of having a blood clot,” Hunt says. This is because fat tissue secretes inflammatory proteins that make the blood more prone to clotting, and excess abdominal fat puts pressure on pelvic veins, which can affect circulation to the legs.
Stop smoking
Chemicals in tobacco smoke, including nicotine, make the blood “stickier”, slowing blood flow and increasing the risk of clots.
Keep active
“If you sit still in a chair for 90 minutes and don’t move your legs, the blood flow through your veins, especially behind your knees, drops by 50 per cent,” says Hunt. “If you’re on a long-haul flight, keep getting up and moving about. The more mobile you are, the better.”
When travelling for more than three hours, wear loose clothing, avoid alcohol and drink plenty of water. Moving your toes and ankles around can also stimulate blood flow. According to Hunt, flight socks may help to reduce swelling in your legs, but there’s no evidence that they can prevent clots.
Stay hydrated
“If you’re dehydrated, it will make your blood a little bit more sticky, so it’s important to drink adequately, especially when you exercise,” says Hunt.
Choose transdermal hormone replacement therapy (HRT): “The risk of blood clot depends very much on the type of HRT being used,” says Dr Louise Newson, a GP and hormone specialist. “Oral ethinylestradiol tablets and older synthetic progestogens are associated with a small increased risk of clot, whereas body identical estradiol does not increase clot risk, especially when used as a patch, gel or spray.”
Know your risk
“When you go to hospital in the UK, your risk of DVT will automatically be assessed and you will be offered blood thinners if your risk is high,” says Hunt. “GPs will ask if there’s a family history of clots before prescribing the contraceptive pill. If there is, they should prescribe the progesterone-only pill, as the oestrogen in the combined pill slightly increases the risk of clotting.”
How is DVT diagnosed and treated?
If your doctor suspects DVT, a simple blood test called a D-dimer can detect a protein fragment that your body makes when a blood clot dissolves. It’s usually detectable only at a low level unless your body is forming or breaking down blood clots.
“If the D-dimer result is raised, you would then have an ultrasound scan of the leg, followed by some further imaging of the chest,” says Hunt. “If a clot is present, most people start taking anticoagulant medication and get better over a period of a few weeks. If someone is very unwell, they would usually be admitted to hospital and, in some cases, the blood clot may be removed via a procedure called catheter-directed embolectomy.” This involves a tube being inserted in the groin or the neck so the clot can be removed using suction.