Deep vein thrombosis signs and symptoms can include:

Swelling in the affected leg. Rarely, there's swelling in both legs.

• Pain in your leg. The pain often starts in your calf and can feel like cramping or soreness.
• Red or discolored skin on the leg.
• A feeling of warmth in the affected leg.

Deep vein thrombosis can occur without noticeable symptoms.

The warning signs and symptoms of a pulmonary embolism include:

• Sudden shortness of breath
• Chest pain or discomfort that worsens when you take a deep breath or when you cough
• Feeling lightheaded or dizzy, or fainting
• Rapid pulse
• Coughing up blood

The blood clots of deep vein thrombosis can be caused by anything that prevents your blood from circulating or clotting normally, such as injury to a vein, surgery, certain medications and limited movement.

Many factors can increase your risk of developing deep vein thrombosis (DVT). The more you have, the greater your risk of DVT. Risk factors include:

• Inheriting a blood-clotting disorder. Some people inherit a disorder that makes their blood clot more easily. This condition on its own might not cause blood clots unless combined with one or more other risk factors.
• Prolonged bed rest, such as during a long hospital stay, or paralysis. When your legs remain still for long periods, your calf muscles don't contract to help blood circulate, which can increase the risk of blood clots.
• Injury or surgery. Injury to your veins or surgery can increase the risk of blood clots.
• Pregnancy. Pregnancy increases the pressure in the veins in your pelvis and legs. Women with an inherited clotting disorder are especially at risk. The risk of blood clots from pregnancy can continue for up to six weeks after you have your baby.
• Birth control pills (oral contraceptives) or hormone replacement therapy. Both can increase your blood's ability to clot.
• Being overweight or obese. Being overweight increases the pressure in the veins in your pelvis and legs.
• Smoking. Smoking affects blood clotting and circulation, which can increase your risk of DVT.
• Cancer. Some forms of cancer increase substances in your blood that cause your blood to clot. Some forms of cancer treatment also increase the risk of blood clots.
• Heart failure. This increases your risk of DVT and pulmonary embolism. Because people with heart failure have limited heart and lung function, the symptoms caused by even a small pulmonary embolism are more noticeable.
• Inflammatory bowel disease. Bowel diseases, such as Crohn's disease or ulcerative colitis, increase the risk of DVT.
• A personal or family history of deep vein thrombosis or pulmonary embolism.If you or someone in your family has had one or both of these, you might be at greater risk of developing a DVT.
• Age. Being older than 60 increases your risk of DVT, though it can occur at any age.
• Sitting for long periods of time, such as when driving or flying. When your legs remain still for hours, your calf muscles don't contract, which normally helps blood circulate. Blood clots can form in the calves of your legs if your calf muscles don't move for long periods.

Pulmonary embolism

A serious complication associated with deep vein thrombosis is pulmonary embolism.

Pulmonary embolism

A pulmonary embolism occurs when a blood vessel in your lung becomes blocked by a blood clot (thrombus) that travels to your lung from another part of your body, usually your leg.

A pulmonary embolism can be life-threatening. It's important to watch for signs and symptoms of a pulmonary embolism and seek medical attention if they occur. Signs and symptoms of a pulmonary embolism include:

• Sudden shortness of breath
• Chest pain or discomfort that worsens when you take a deep breath or when you cough
• Feeling lightheaded or dizzy, or fainting
• Rapid pulse
• Coughing up blood

Postphlebitic syndrome

A common complication that can occur after deep vein thrombosis is known as postphlebitic syndrome, also called postthrombotic syndrome. Damage to your veins from the blood clot reduces blood flow in the affected areas, which can cause:

• Persistent swelling of your legs (edema)
• Leg pain
• Skin discoloration
• Skin sores