What Is It, Causes, Signs and Symptoms, and More

Author:Anna Hernández, MD

Editors:Alyssa Haag,Emily Miao, PharmD,Kelsey LaFayette, DNP, RN, FNP-C

Illustrator:Jessica Reynolds, MS

Copyeditor:Sadia Zaman, MBBS, BSc

What is phlebitis?

Phlebitis refers to the acute inflammation of a vein and is characterized by pain, tenderness, swelling, and redness around the affected area. 

In most cases, inflammation is caused by a blood clot, or thrombus, and is therefore referred to as thrombophlebitis. Thrombophlebitis most often occurs in superficial leg veins, where it is called superficial thrombophlebitis, and deeper leg veins, where it is called deep vein thrombosis (DVT). Although thrombophlebitis typically affects the lower leg, it can also develop in other areas of the body including the breast or penis, and sites of IV insertion.

Dorsal aspect of hand showing inflamed veins.

What causes phlebitis?

Phlebitis is caused by the inflammation of a vein, often due to the presence of an underlying blood clot. There are three main risk factors that lead to thrombosis, which are referred to as Virchow’s triad. The first factor is slowed blood flow, called stasis, in the veins. Stasis can happen during long periods of inactivity, such as in prolonged bed rest; long car rides and flights; a sedentary lifestyle; or due to varicose veins, where decreased venous outflow causes the formation of static pockets of blood. The second factor in the Virchow triad is a state of hypercoagulation, where there is an increased tendency to develop blood clots. Causes of hypercoagulability include genetic clotting disorders (e.g., factor V Leiden, prothrombin gene mutation, protein C and S deficiency, or antithrombin III deficiency), surgery, trauma, or certain medications, such as oral contraceptive pills. Finally, the third factor in Virchow’s triad is damage to the inner lining of blood vessels; this can be caused by infections, chronic inflammation, or toxins, like those found in tobacco cigarettes.

Phlebitis involving the upper limb is less common and generally occurs as a complication of IV cannulation. Mechanical phlebitis occurs when the movement of the IV line within the vein causes friction and damages the blood vessel walls. This typically happens when the size of the cannula is too large for the selected vein, or when placement of the cannula is too close to a mobile joint or venous valve. On the other hand, chemical phlebitis is caused by the infusion of highly irritant intravenous medications (e.g., chemotherapy, vasopressors, or high doses of potassium chloride). In order to prevent phlebitis, these medications are typically administered via a central line. Finally, infective phlebitis, or septic thrombophlebitis, occurs when bacteria is introduced into the bloodstream via an intravenous injection or catheter placement. It is typically associated with poor hygiene practices and high frequency of medication administration. 

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What are the signs and symptoms of phlebitis?

Common signs and symptoms of phlebitis include pain, swelling, redness, and warmth around the affected area. The affected vein can swell, leading to palpable, hard lumps underneath the skin. The lump is typically painful to touch. Phlebitis usually occurs on the legs, but it can also affect the veins in the arms and, on rare occasions, in the penis or breast (i.e., Mondor disease).

In some cases of superficial thrombophlebitis, the blood clot may travel along the superficial vein to a deep vein, causing a DVT. This is more common if the clot is located where large superficial veins intersect with the deep venous system, such as the groin, upper thigh, or behind the knee. The main complication of a DVT is pulmonary embolism, which happens when parts of the clot break off and travel to the lungs, causing a blockage in one of the pulmonary arteries or its branches. This is a life-threatening situation that prevents blood from entering the lungs to receive oxygen, resulting in decreased oxygen saturation, sudden shortness of breath, and chest pain. 

How is phlebitis diagnosed?

Phlebitis is typically diagnosed clinically based on the individual’s clinical presentation and findings on the physical examination. If thrombophlebitis is suspected, a Wells score can be obtained to determine the individual’s risk of developing deep vein thrombosis (DVT) before any further testing occurs.  The Wells score takes into account the individual’s current signs and symptoms, as well as the presence of certain risk factors that increase the risk of thrombosis (e.g., prior history of DVT, recent bedrest, or active cancer).. 

If there is a high risk of DVT, an ultrasound may be performed to confirm the presence of a blood clot and assess its location. In cases where thrombophlebitis cannot be ruled out, a D-dimer blood test can be helpful, as fibrin break-down products levels like D-dimer are usually higher in the presence of a clot.

ow is phlebitis treated?

Most symptoms of phlebitis resolve over the course of a few days with supportive measures, which include medications to help relieve the pain (e.g., NSAIDs or acetaminophen), elevating the leg to prevent swelling, compression stockings and applying warm compresses to the affected area. For individuals with superficial thrombophlebitis, a venous cord (i.e., hard, cord-like induration) may remain palpable for several months after resolution of the symptoms. 

While some small blood clots resolve on their own over time, large clots that cause symptoms typically require treatment to resolve. Treatment may involve blood thinning or anticoagulant medications, like warfarin or heparin, which inhibit the clotting cascade and prevent clot formation. In cases where there is extensive thrombosis, thrombolytic enzymes, such as urokinase or streptokinase, may be given to help break down the clot, or a thrombectomy can be conducted to surgically remove the clot.

Prevention of thrombophlebitis is recommended in individuals with chronic varicose veins and for individuals who may be immobile for long periods of time (e.g., prolonged bedrest, long car rides or flights, etc.). Prevention consists of compression stockings and frequent calf exercises to help move blood through the veins and prevent stasis.

What are the most important facts to know about phlebitis?

Phlebitis refers to the inflammation of a vein. In most cases, inflammation is caused by a blood clot, and is thereby called thrombophlebitis. Thrombophlebitis most often develops in the legs and can be categorized as either superficial thrombophlebitis or deep vein thrombosis (DVT). Nonetheless, it can also occur in other areas of the body, particularly at sites of IV insertion. Symptoms of thrombophlebitis include pain, swelling, redness, and warmth around the course of the affected vein. Treatment is aimed at relieving local symptoms and preventing thromboembolic complications, which can include pulmonary embolisms.

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Related links

Artery and vein histology
Deep vein thrombosis
Pulmonary embolism

Resources for research and reference

Guanche-Sicilia, A., Sánchez-Gómez, M. B., Castro-Peraza, M. E., Rodríguez-Gómez, J. Á., Gómez-Salgado, J., & Duarte-Clíments, G. (2021). Prevention and Treatment of Phlebitis Secondary to the Insertion of a Peripheral Venous Catheter: A Scoping Review from a Nursing Perspective. Healthcare, 9(5): 611. DOI:10.3390/healthcare9050611 

Josephson, S. A., Ropper, A. H., & Hauser, S. L. (2022). Coma. In J. Loscalzo, A. Fauci, D. Kasper, S. Hauser, D. Longo, & J. L. Jameson (Eds.), Harrison’s Principles of Internal Medicine (21st ed.). McGraw-Hill Education. 

Ortel, T. L., Neumann, I., Ageno, W., Beyth, R., Clark, N. P., Cuker, A., & Zhang, Y. (2020). American Society of Hematology 2020 guidelines for management of venous thromboembolism: treatment of deep vein thrombosis and pulmonary embolism. Blood Advances, 4(19): 4693–4738. DOI:10.1182/bloodadvances.2020001

Scovell, S., Eidt, J. F., Mills, J. L., & Collins, K.A. (2022).Superficial vein thrombosis and phlebitis of the lower extremity veins. In UpToDate. Retrieved July 10, 2022, from

Senst, B., Tadi, P., Goyal, A., & Jan, A. (2020). Hypercoagulability.  In StatPearls [Internet]. Retrieved August 25, 2022, from