Overview
A DVT usually forms in the calf or thigh. It may cause swelling of one leg, pain or tenderness (often like a cramp), warmth, and red or darker skin. Some DVTs cause no symptoms.
Risk is higher after surgery, long trips, bed rest, or a leg injury, and with cancer, pregnancy, birth control pills or hormone therapy, smoking, obesity, and a past clot. Cellulitis (skin infection) and a burst Baker's cyst can look similar, so testing is needed.
When to get medical care
Causes
Common causes include deep vein thrombosis, cellulitis, a ruptured Baker's cyst, muscle strain or tear, and superficial vein clots. Risk factors for DVT include surgery, hospital stays, long travel, cancer, pregnancy, hormone medicines, smoking, obesity, older age, and inherited clotting disorders.
OwieClear has pages on 6 conditions that can cause one leg or calf swollen, warm, and tender. Each shows how soon to get care.
Common causes
- Blood clot in the leg (deep vein thrombosis)Often needs care today
A blood clot in a deep vein, usually in one leg.
Less likely causes
- Blood clot in the lung (pulmonary embolism)May need emergency care
A blood clot, usually from the leg, that travels to the lungs.
- Essential thrombocythemiaSee a doctor if it doesn't get better
A slow-growing blood cancer where the bone marrow makes too many platelets.
- Myeloproliferative neoplasms (polycythemia vera, essential thrombocythemia, myelofibrosis)See a doctor if it doesn't get better
Slow-growing blood cancers in which the bone marrow makes too many red cells, platelets, or scar tissue.
- Ovarian clear cell carcinomaSee a doctor if it doesn't get better
An uncommon ovarian cancer linked to endometriosis.
- Polycythemia veraSee a doctor if it doesn't get better
A slow-growing blood cancer where the bone marrow makes too many red blood cells.
What you can do at home
- Get checked the same day.
- Don't massage the leg if a clot is possible.
- Take blood thinners exactly as prescribed if you have a DVT.
- Walk and move as your provider advises.
- Wear compression stockings if recommended.
Medicines
DVT is treated with blood thinners (anticoagulants), usually for at least 3 months. Some people need a filter or clot-removal procedure. Cellulitis needs antibiotics.
At the doctor
An ultrasound is the main test for a leg clot.
Questions you may be asked
- When the swelling started
- Recent surgery, travel, or injury
- Past clots or family history
- Hormone medicines or pregnancy
- Shortness of breath or chest pain
The exam
A physical exam comparing both legs.
Tests
- A Doppler ultrasound of the leg
- A D-dimer blood test
- A CT scan of the chest if a lung clot is possible
Prevention
You can lower your risk.
- Move and stretch on long trips
- Get up and walk soon after surgery
- Don't smoke
- Keep a healthy weight
Check your symptoms
Most symptoms have more than one possible cause. The symptom checker looks at all of your symptoms together, plus your age, and shows how soon to get care.
Sources
Last updated 2026-11-13.