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Formation of a blood clot in a vein
Normal blood flow
Normally, one-way valves in the veins keep blood flowing to the heart.
Blood clot forming
A blood clot can form when the valve in a vein does not work properly. If the valve does not open normally, blood cells can collect behind the valve and begin to stick together to form a clot.
Formed blood clot
When a blood clot gets large enough, it can stop the flow of blood in the vein.
Current as of: October 2, 2025
Author: Ignite Healthwise, LLC Staff
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