In short
A deep vein thrombosis is a blood clot, usually in the leg, that needs prompt treatment because part of it can break off and travel to the lungs.
Emergency if: Sudden shortness of breath, chest pain that worsens with breathing, a racing heart, coughing up blood, or feeling faint — any one of these alone can mean the clot has reached the lungs. Call emergency services now.
On your report
D-dimer
On this page
01
What a DVT Is
Deep vein thrombosis, or DVT, is a blood clot that forms in a deep vein, most often in the calf or thigh. It's more likely after prolonged immobility — a long flight or car ride, hospitalization, or recovery from surgery — as well as with pregnancy, estrogen-containing birth control or hormone therapy, active cancer, certain inherited clotting disorders, and smoking.
The danger isn't only the clot itself but where it can go: a piece can break loose and travel through the bloodstream to the lungs, called a pulmonary embolism, which can be life-threatening.
02
Recognizing the Signs
Typical symptoms are swelling, warmth, redness, and pain or tenderness in one leg — usually the calf — that develops over hours to a couple of days, often without an obvious injury to explain it. The affected leg may look visibly larger than the other.
Sudden shortness of breath, chest pain that worsens with breathing, a rapid heartbeat, coughing up blood, or feeling faint are signs the clot may have reached the lungs. Any one of these on its own — shortness of breath alone is common — is a medical emergency requiring immediate care; call emergency services rather than driving yourself.
03
How It's Diagnosed
A D-dimer blood test is often used as a first step: a normal result in someone with low clinical suspicion makes a DVT unlikely and can avoid further testing, though an elevated result doesn't confirm a clot on its own, since many other conditions raise it too. Ultrasound of the leg is the standard way to directly confirm or rule out a clot.
When a pulmonary embolism is suspected, a CT scan of the chest with contrast dye is the usual next step to look directly for a clot in the lung's blood vessels.
04
Treatment
Blood-thinning medication (anticoagulation) is the mainstay of treatment, preventing the existing clot from growing and reducing the risk of a new one forming while the body gradually breaks down the current clot over weeks to months. Most people start treatment right away, often the same day the diagnosis is confirmed.
Compression stockings can help with swelling and discomfort during recovery. Rarely, for very large or limb-threatening clots, a procedure to remove the clot directly may be used. The typical duration of blood thinning ranges from a few months to indefinitely, depending on the cause and whether the risk of a future clot remains high.
05
Prevention
Moving regularly during long trips, staying active after surgery or hospitalization as soon as it's safe to do so, and following any blood-thinning precautions prescribed after a major operation are the main preventive steps for those at elevated risk.
Anyone with new one-sided leg swelling and pain — especially with a recent long trip, surgery, hospitalization, or pregnancy — should be seen the same day rather than waiting to see if it improves, since early treatment is what prevents the clot from reaching the lungs.
How urgent is it?
Same-day — call promptly
New one-sided leg swelling, warmth, and pain developing over hours to days — get evaluated the same day, especially after a long trip, surgery, or with pregnancy.
Emergency — act now
Sudden shortness of breath, chest pain that worsens with breathing, a racing heart, coughing up blood, or feeling faint — any one of these alone can mean the clot has reached the lungs. Call emergency services now.
Values mentioned in this story
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Sources
- Deep Vein Thrombosismedlineplus.gov
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