Secretary of State Hilary Clinton was hospitalized Sunday for a blood clot that formed after her she fell and suffered a concussion a few weeks ago.

The clot was discovered during a follow-up exam related to the concussion, said Clinton's spokesman, Philippe Reines, deputy assistant secretary of state. Clinton, 65, was expected to remain at New York Presbyterian Hospital for the next 48 hours for monitoring and treatment with anticoagulants - drugs that prevent clots from forming or prevent them from growing larger.

Reines said Clinton's clot was found in the vein located in the space between the brain and the skull behind the right ear. "It did not result in a stroke, or neurological damage. To help dissolve this clot, her medical team began treating the Secretary with blood thinners," said Clinton's doctors in a written statement.

Blood clots most often develop deep in leg veins, and symptoms are easily missed. The medical term for blood clots developing in the large veins of the leg or pelvis is deep vein thrombosis (DVT). An estimated 2 million Americans develop DVT each year.

Here are the four things you need to know about blood clots:

1. DVT is not life-threatening (most of the time)

Most cases of DVT are simply treated with a blood thinner that breaks up the clot and prevents it from migrating to different areas in the body. However, if left untreated, DVT can result in a pulmonary embolism, which occurs when the blood clot travels from the leg to the lungs. It accounts for nearly 200,000 deaths a year.

2. Travelers have the highest risk

A large long-term study published in the journal PLoS One in 2007 found the more frequently a person travels, the higher their risk. This is because blood clots are generally caused by sluggish blood flow through the vein, usually from sitting in cramped positions for long periods of time. Experts say most cases of DVT develop on flights over four hours in length. Some studies show the cabin pressure of an airplane also plays a role. Most people think DVT strikes just older adults, but research shows that women taking birth control pills, people over 6 feet 1 inch tall, and adults under 30 are at increased risk.

3. There are warning signs