There are two forms of phlebitis. The most common form is swelling of a vein near the skin's surface, usually in the leg. This is called superficial phlebitis. Swelling of the veins inside the leg is less common but more serious. This is called deep phlebitis.

For superficial phlebitis, the area looks reddish and feels painful. The pain of this condition can usually be treated with moist heat, aspirin, or anti-inflammatory medicines.

The more dangerous form is deep phlebitis which usually causes greater pain. People with deep phlebitis tend to have a fever. Nuclear scans, venous Doppler flow studies, or the use of a blood pressure cuff around the leg to measure blood flow (plethysmography) will usually confirm if the deep veins are involved. This type is more likely to lead to blood clots in the veins and a possible blood clot in the lungs (pulmonary embolus). If you are diagnosed with deep phlebitis, doctors will usually give you a week-long treatment with a blood-thinning, or anticoagulant, medicine. During this time, doctors will also check for signs of blood clots in your lungs. Your doctor will probably give you an anticoagulant in pill-form to be taken longer-term.