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The most obvious symptoms of deep vein thrombosis (DVT) are swelling or pain in the calf or thigh of one leg, or both swelling and pain.

The affected part of the leg can also:¹

• Feel hot
• Turn red or purple.

But some people with DVT do not get any symptoms.

If you get a blood clot and it travels to the artery of one of your lungs (a pulmonary embolism), you can:¹

• Get breathless
• Feel dizzy
• Have chest pains
• Cough up blood
• Feel your heart racing.

Some of these symptoms can happen with other illnesses, not just DVT or pulmonary embolism.

To find out if you have DVT, your doctor will want to know about your symptoms as well as your health in general. They will also examine your affected leg. But doctors can't tell if you have DVT simply by examining you. If your doctor thinks you could have DVT, they will send you for some tests right away.

• You will probably need an ultrasound scan to see if there's a blood clot in your leg. This scan is good at detecting clots above your knee but less good at spotting clots below your knee.
• You might be offered a blood test that can tell doctors whether you have a high or low chance of having DVT. This is called the D-dimer blood test.
• If your doctor is still unsure about whether you have DVT, you might need a special type of X-ray where you have dye injected into a vein. This is called venography.
• If your doctor thinks you have a clot in your calf, you may need another ultrasound scan in about a week to find out whether the clot has traveled above your knee (this is called proximal DVT). If you have proximal DVT, part of the clot is more likely to break off and travel to your lungs. This is called a pulmonary embolism and it is dangerous.

To find out if you have a pulmonary embolism, you'll need other hospital tests, including scans of your lungs.

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.