Deep vein thrombosis (DVT) occurs when a blood clot (thrombus) forms in one or more of the deep veins in your body, usually in your legs. Deep vein thrombosis can cause leg pain or swelling but also can occur with no symptoms.
You can get DVT if you have certain medical conditions that affect how your blood clots. A blood clot in your legs can also happen if you don't move for a long time, such as after you have surgery or an accident, when you're traveling a long distance, or when you're on bed rest.
Deep vein thrombosis can be very serious because blood clots in your veins can break loose, travel through your bloodstream and get stuck in your lungs, blocking blood flow (pulmonary embolism). However, pulmonary embolism can occur with no evidence of DVT.
When DVT and pulmonary embolism occur together, it's called venous thromboembolism (VTE).
DVT signs and symptoms can include:
Swelling in the affected leg. Rarely, there's swelling in both legs.
Pain in your leg. The pain often starts in your calf and can feel like cramping or soreness.
Red or discolored skin on the leg.
A feeling of warmth in the affected leg.
Deep vein thrombosis can occur without noticeable symptoms.
When to see a doctor
If you develop signs or symptoms of DVT, contact your doctor.
If you develop signs or symptoms of a pulmonary embolism (PE) — a life-threatening complication of deep vein thrombosis — seek emergency medical help.
The warning signs and symptoms of a pulmonary embolism include:
Sudden shortness of breath
Chest pain or discomfort that worsens when you take a deep breath or when you cough
Feeling lightheaded or dizzy, or fainting
Coughing up blood
Anything that prevents your blood from flowing or clotting normally can cause a blood clot.
The main causes of DVT are damage to a vein from surgery or trauma and inflammation due to infection or injury.
Many things can increase your risk of developing DVT. The more risk factors you have, the greater your risk of DVT. Risk factors for DVT include:
Age. Being older than 60 increases your risk of DVT, though it can occur at any age.
Sitting for long periods of time, such as when driving or flying. When your legs remain still for hours, your calf muscles don't contract. Muscle contractions normally help blood circulate.
Prolonged bed rest, such as during a long hospital stay, or paralysis. Blood clots can form in the calves of your legs if your calf muscles don't move for long periods.
Injury or surgery. Injury to your veins or surgery can increase the risk of blood clots.
Pregnancy. Pregnancy increases the pressure in the veins in your pelvis and legs. Women with an inherited clotting disorder are especially at risk. The risk of blood clots from pregnancy can continue for up to six weeks after you have your baby.
Birth control pills (oral contraceptives) or hormone replacement therapy. Both can increase your blood's ability to clot.
Being overweight or obese. Being overweight increases the pressure in the veins in your pelvis and legs.
Smoking. Smoking affects blood clotting and circulation, which can increase your risk of DVT.
Cancer. Some forms of cancer increase substances in your blood that cause your blood to clot. Some forms of cancer treatment also increase the risk of blood clots.
Heart failure. This increases your risk of DVT and pulmonary embolism. Because people with heart failure have limited heart and lung function, the symptoms caused by even a small pulmonary embolism are more noticeable.
Inflammatory bowel disease. Bowel diseases, such as Crohn's disease or ulcerative colitis, increase the risk of DVT.
A personal or family history of DVT or PE. If you or someone in your family has had one or both of these, you might be at greater risk of developing DVT.
Genetics. Some people inherit genetic risk factors or disorders, such as factor V Leiden, that make their blood clot more easily. An inherited disorder on its own might not cause blood clots unless combined with one or more other risk factors.
No known risk factor. Sometimes, a blood clot in a vein can occur with no apparent underlying risk factor. This is called an unprovoked VTE.
Complications of DVT can include:
Pulmonary embolism (PE). PE is a potentially life-threatening complication associated with DVT. It occurs when a blood vessel in your lung becomes blocked by a blood clot (thrombus) that travels to your lung from another part of your body, usually your leg.
It's important to get immediate medical help if you have signs and symptoms of PE. Sudden shortness of breath, chest pain while inhaling or coughing, rapid breathing, rapid pulse, feeling faint or fainting, and coughing up blood may occur with a PE.
Postphlebitic syndrome. Damage to your veins from the blood clot reduces blood flow in the affected areas, causing leg pain and swelling, skin discoloration and skin sores.
Treatment complications. Complications may result from blood thinners used to treat DVTs. Bleeding (hemorrhage) is a worrisome side effect of blood thinners. It's important to have regular blood tests while taking such medications.
Measures to prevent deep vein thrombosis include the following:
Avoid sitting still. If you have had surgery or have been on bed rest for other reasons, try to get moving as soon as possible. If you're sitting for a while, don't cross your legs, which can block blood flow. If you're traveling a long distance by car, stop every hour or so and walk around.
If you're on a plane, stand or walk occasionally. If you can't do that, exercise your lower legs. Try raising and lowering your heels while keeping your toes on the floor, then raising your toes with your heels on the floor.
Don't smoke. Smoking increases your risk of getting DVT.
Exercise and manage your weight. Obesity is a risk factor for DVT. Regular exercise lowers your risk of blood clots, which is especially important for people who sit a lot or travel frequently.
To diagnose DVT, your doctor will ask you about your symptoms. You'll also have a physical exam so that your doctor can check for areas of swelling, tenderness or changes in skin color.
The tests you have depend on whether your doctor thinks you are at a low or a high risk of DVT. Tests used to diagnose or rule out a blood clot include:
D-dimer blood test. D dimer is a type of protein produced by blood clots. Almost all people with severe DVT have increased blood levels of D dimer. A normal result on a D-dimer test often can help rule out PE.
Duplex ultrasound. This noninvasive test uses sound waves to create pictures of how blood flows through your veins. It's the standard test for diagnosing DVT. For the test, a technician gently moves a small hand-held device (transducer) on your skin over the body area being studied. Sometimes a series of ultrasounds are done over several days to determine whether a blood clot is growing or to check for a new one.
Venography. A dye is injected into a large vein in your foot or ankle. An X-ray creates an image of the veins in your legs and feet, to look for clots. The test is invasive, so it's rarely performed. Other tests, such as ultrasound, often are done first.
Magnetic resonance imaging (MRI) scan. This test may be done to diagnose DVT in veins of the abdomen.
There are three main goals to DVT treatment.
Prevent the clot from getting bigger.
Prevent the clot from breaking loose and traveling to the lungs.
Reduce your chances of another DVT.
DVT treatment options include:
Blood thinners. DVT is most commonly treated with anticoagulants, also called blood thinners. These drugs don't break up existing blood clots, but they can prevent clots from getting bigger and reduce your risk of developing more clots.
Blood thinners may be taken by mouth or given by IV or an injection under the skin. Heparin is typically given by IV. The most commonly used injectable blood thinners for DVT are enoxaparin (Lovenox) and fondaparinux (Arixtra).
After taking an injectable blood thinner for a few days, your doctor may switch you to a pill. Examples of blood thinners that you swallow include warfarin (Jantoven) and dabigatran (Pradaxa).
Certain blood thinners do not need to be given first with IV or injection. These drugs are rivaroxaban (Xarelto), apixaban (Eliquis) or edoxaban (Savaysa). They can be started immediately after diagnosis.
You might need to take blood thinner pills for three months or longer. It's important to take them exactly as prescribed to prevent serious side effects.
If you take warfarin, you'll need regular blood tests to check how long it takes your blood to clot. Pregnant women shouldn't take certain blood-thinning medications.
Clot busters. Also called thrombolytics, these drugs might be prescribed if you have a more serious type of DVT or PE, or if other medications aren't working.
These drugs are given either by IV or through a tube (catheter) placed directly into the clot. Clot busters can cause serious bleeding, so they're usually only used for people with severe blood clots.
Filters. If you can't take medicines to thin your blood, you might have a filter inserted into a large vein — the vena cava — in your abdomen. A vena cava filter prevents clots that break loose from lodging in your lungs.
Compression stockings. These special knee socks reduce the chances that your blood will pool and clot. To help prevent swelling associated with deep vein thrombosis, wear them on your legs from your feet to about the level of your knees. You should wear these stockings during the day for at least two years, if possible.
Lifestyle and home remedies
Once you receive treatment for DVT, it's important to follow some lifestyle changes to manage your condition and prevent another blood clot. Lifestyle changes include:
Ask your doctor about your diet. Foods high in vitamin K, such as spinach, kale, other leafy greens and Brussels sprouts, can interfere with warfarin.
Take your medications as directed. Your doctor will tell you how long you will need treatment. If you're taking certain blood thinners, you'll need a blood test to see how well your blood is clotting.
Watch for excessive bleeding. This can be a side effect of blood thinners. Talk to your doctor about activities that could cause you to bruise or get cut, as even a minor injury could become serious if you're taking blood thinners.
Move. If you've been on bed rest because of surgery or other factors, the sooner you get moving, the lower the chance that blood clots will develop.
Wear compression stockings. Wear these to help prevent blood clots in the legs if your doctor recommends them.
Preparing for an appointment
DVT is considered a medical emergency, so it's important to get evaluated quickly. However, if you have time before your appointment, here's some information to help you get ready.
What you can do
Make a list of:
Your symptoms, including any that seem unrelated to deep vein thrombosis, and when they began
Key personal information, including notes about travel, hospital stays, any illness, surgery or trauma in the past three months, and any personal or family history of blood-clotting disorders
All medications, vitamins or other supplements you take, including doses
Questions to ask your doctor
If possible, take a family member or friend with you to help you remember the information you're given.
For DVT, questions to ask your doctor include:
What's the most likely cause of my symptoms?
What tests do I need?
What's the best treatment?
What are the alternatives to the primary approach that you're suggesting?
Will I need to restrict my physical activity or travel?
I have other health conditions. How can I best manage these conditions together?
Are there brochures or other printed material I can have? What websites do you recommend?
What to expect from your doctor
Your doctor is likely to ask you questions, such as:
Have you been inactive lately, such as sitting or lying down for long periods?
Do your symptoms bother you all the time, or do they come and go?