Sitting for long periods of time or a lack of activity may be putting you at risk for a condition called phlebitis. It can be either a superficial medical condition or very quickly it can become life threatening.

The most common form of phlebitis is a superficial swelling of a vein right near the skin's surface. But then there's a less common but more serious form, which is called deep vein thrombosis. Cardiologist Brian Arcement explains "Deep vein thrombosis is clots forming within the veinous structure of the legs."

Dr. Arcement says that the danger with thrombophlebitis or deep vein thrombosis, is the development of clots. "The one primary risk of developing clots in the veins, or the clot breaking loose and traveling up to the heart and including one of the major lung arteries, is called a pulmonary embolism and can be fatal."

Registered nurse Joan Pape-Knoll says, "If you notice that you have pain in your legs or in your calf specifically, or in your thigh. If you notice redness in a cordlike fashion and swelling, that's a medical emergency, you need to go to the emergency room."

Joan also says that certain people are at a higher risk for both types of phlebitis. "If somebody is taking birth control pills it puts then at a higher risk of getting a deep vein thrombosis and I've actually seen a 29 year old female have a stroke because of the fact that she was on birth control pills and are smoking, that's very, very bad."

To avoid phlebitis of any kind you should quit smoking, avoid staying in the same position for too long and exercise too, that promotes circulation.

Phlebitis can also be a complication of certain diseases such as lupus, or of pancreatic, breast, or ovarian cancers.