What is a blood clot?
A blood clot (thrombus) forms when blood changes from a liquid to a gel-like substance and blocks a blood vessel. Clots can form in veins (venous thrombosis) or arteries. This website provides information about venous clots — the type most commonly treated with blood-thinning medications.
Learn about your condition
Leg DVT
Deep vein thrombosis in the leg — clots in the deep veins of the calf, thigh, or pelvis.
Arm DVT
Deep vein thrombosis in the arm — clots in the shoulder, underarm, or arm veins.
Leg SVT
Superficial vein thrombosis — a clot in a vein just under the skin of the leg.
Arm SVT
Superficial vein thrombosis in the arm — often at an IV or blood draw site.
Pulmonary Embolism
A blood clot that has traveled to the lungs and is blocking blood flow.
Splanchnic VT
Clots in the veins that drain the intestines, liver, and spleen.
CVST
Cerebral venous sinus thrombosis — clots in the brain's venous drainage channels.
When to call 911 or go to Emergency
If you experience sudden shortness of breath, chest pain, coughing up blood, stroke symptoms (face drooping, arm weakness, speech difficulty), or severe worsening of your symptoms — call 911 or go to the nearest Emergency Department immediately.