Thrombophlebitis is a condition that causes a blood clot to form and block one or more veins, often in the legs. In superficial thrombophlebitis, the vein is near the surface of the skin. In deep vein thrombosis or DVT, the vein is deep within a muscle. DVT increases the risk of serious health problems. Both types of thrombophlebitis can be treated with blood-thinning medications.

Thrombophlebitis (throm-boe-fluh-BY-tis) is an inflammatory process that causes a blood clot to form and block one or more veins, usually in the legs. The affected vein might be near the surface of the skin (superficial thrombophlebitis) or deep within a muscle (deep vein thrombosis, or DVT).

Causes of thrombophlebitis include trauma, surgery or prolonged inactivity.

Deep vein thrombosis (DVT) increases the risk of serious health problems. It's usually treated with blood-thinning medications. Superficial thrombophlebitis is sometimes treated with blood-thinning medications, too.


Symptoms of superficial thrombophlebitis include warmth, tenderness, and pain. You might have redness and swelling and see a red, hard cord just under the surface of your skin that's tender to the touch. Symptoms of deep vein thrombosis include swelling, tenderness, and pain in your leg.

Superficial thrombophlebitis signs and symptoms include:

  • Warmth, tenderness and pain in the affected area
  • Redness and swelling

Deep vein thrombosis signs and symptoms include:

  • Pain
  • Swelling

When a vein close to the surface of the skin is affected, you might see a red, hard cord just under the surface of the skin that's tender to the touch. When a deep vein in the leg is affected, the leg may become swollen, tender and painful.

When to see a doctor

See your doctor right away if you have a red, swollen or tender vein — especially if you have one or more risk factors for thrombophlebitis.

Call 911 or your local emergency number if:

  • The vein swelling and pain are severe
  • You also have shortness of breath or chest pain, are coughing up blood, or have other symptoms that may indicate a blood clot traveling to your lungs (pulmonary embolism)

Have someone take you to your doctor or emergency room, if possible. It might be difficult for you to drive, and it's helpful to have someone with you to help you remember the information you receive.


Thrombophlebitis is caused by a blood clot. A blood clot can form because of an injury to a vein or from having an inherited disorder that affects how your blood clots. You may also get a blood clot after not being active for long periods of time, like during a hospital stay or recovery from an injury.

The cause of thrombophlebitis is a blood clot, which can form in your blood as a result of:

  • An injury to a vein
  • An inherited blood-clotting disorder
  • Being immobile for long periods, such as during an injury or a hospital stay

Risk factors

Your risk of thrombophlebitis is higher if you're not active for a long period or you have a catheter in a central vein to treat a condition. Having varicose veins or a pacemaker can also increase your risk. Women who are pregnant, have just given birth, or take birth control pills or hormone replacement therapy may also be at higher risk. Other risk factors include a family history of a blood-clotting disorder, a tendency to form blood clots, and having thrombophlebitis before. Your risk may also be higher if you've had a stroke, you're over age 60, or you're overweight. Having cancer and smoking are also risk factors.

Your risk of thrombophlebitis might increase if you:

  • Are inactive for a prolonged period, either because you're confined to bed or you're traveling in a car or plane for a long period
  • Have varicose veins, which are a common cause of superficial thrombophlebitis
  • Have a pacemaker or have a thin, flexible tube (catheter) in a central vein, for treatment of a medical condition, which may irritate the blood vessel wall and decrease blood flow
  • Are pregnant or have just given birth
  • Use birth control pills or hormone replacement therapy, which can make your blood more likely to clot
  • Have a family history of a blood-clotting disorder or a tendency to form blood clots
  • Have had previous episodes of thrombophlebitis
  • Have had a stroke
  • Are older than 60
  • Are overweight or obese
  • Have cancer
  • Smoke

If you have one or more risk factors, discuss prevention strategies with your doctor before taking long flights or road trips or if you're planning to have elective surgery, recovery from which will require you not to move much.


Complications from superficial thrombophlebitis are rare. However, if you develop deep vein thrombosis (DVT), the risk of serious complications increases. Complications might include:

  • Blood clot in the lungs (pulmonary embolism). If part of a deep vein clot becomes dislodged, it can travel to your lungs, where it can block an artery (embolism) and become potentially life-threatening.
  • Lasting leg pain and swelling (post-phlebetic syndrome). This condition, also known as post-thrombotic syndrome, can develop months or years after you've had DVT. The pain can be disabling.


Sitting during a long flight or car ride can cause your ankles and calves to swell and increases your risk of thrombophlebitis. To help prevent a blood clot:

  • Take a walk. If you're flying or riding a train or bus, walk up and down the aisle once an hour or so. If you're driving, stop every hour or so and move around.
  • Move your legs regularly. Flex your ankles, or carefully press your feet against the floor or footrest in front of you at least 10 times each hour.
  • Drink plenty of water or other nonalcoholic fluids to avoid dehydration.