A blood clot is simply blood that has clumped together through a process known as thrombosis. It can happen in any vein of your body, but is most common in the deep veins, hence the term “deep vein thrombosis” or DVT. The calf is a typical location, but blood clots can also develop in your thighs, arms or groin.

A Look Inside Your Pipeline
Much like the pipes that carry water to and from your kitchen sink, blood vessels transport blood to and from your heart. Your arteries transport oxygen-rich blood from your heart to the rest of your body while your veins carry oxygen-poor blood in the opposite direction, that is, back to your heart. Your body has two major types of veins: superficial veins, which are closer to your skin and easier to see; and deep veins, which are buried within your muscles. Both types of veins are connected by perforating veins, which allow blood to move between the two of them. As deep veins carry blood from different organs in your body, they join via a complex web and run into the vena cava, your body’s largest vein and one of the main “pipes” to your heart. Deep veins rely on the squeezing and contraction of surrounding muscles to help them push blood towards your heart, hence the importance of physical exercise.

Causes & Risk Factors
Since slow-moving or stagnant blood has a tendency to clump, any condition that slows the flow of blood in your veins can lead to a blood clot. It could be immobility, an injury to your veins, or even a natural tendency for your blood to clot (known as hypercoagulability). Typically, however, your risk of forming a blood clot increases with the following:
•    Older age, especially above 60
•    A previous history of blood clots
•    A family history of blood clots
•    Recent pacemaker catheter through the veins in your groin
•    Prolonged bedrest  
•    Cigarette smoking
•    Fractures in your pelvis or legs
•    Recent childbirth
•    Heart failure or heart attack
•    Obesity
•    Recent surgery in your hip, knee, or female pelvic area
•    Too many blood cells being made by the bone marrow (polycythemia vera)
•    Cancer
•    Taking estrogens or birth control pills, especially if you smoke.
•    Prolonged sitting, especially if other risk factors are also present.

Signs and Symptoms
Do not dismiss any of the following:
•    Sudden swelling in your leg
•    Progressing pain or tenderness
•    Increased pain to the calf when bending your foot upwards
•    Increased warmth in your skin
•    Noticeably enlarged superficial veins
•    Skin color changes (blue, red or very pale)

Here’s a good starting point to help reduce your risk of developing a blood clot:
•    If you’re a smoker, make it a goal to stop
•    Avoid standing or sitting for more than an hour at a time
•    Move and stretch your legs often during long periods of sitting or standing
•    Wear compression stockings, if prescribed
•    Raise your legs above your heart level when sleeping or relaxing
•    Do not place pillows directly beneath your knees when you sleep
•    Lose excess weight
•    Exercise
•    Wear loose-fitting clothes and socks

Blood clots are not usually life-threatening, unless they break loose and travel to the lungs via the bloodstream. This condition is known as pulmonary embolism (PE) and often leads to death within an hour, according to the Vascular Disease Foundation. A traveling clot, known as “embolus,” can also travel to your brain or heart and cause damage. To be safe, call your doctor at the first signs of a blood clot.