"Hypo" means "low level". Hypovolemia means "a low blood volume". It is a common problem, for many reasons. When patients have a lot of swelling, fluid moves out of the blood and into the tissues. There must be an adequate volume of blood in the blood vessels to create a blood pressure.

Some disease states cause the blood vessels to relax and dilate (get bigger). Dilated blood vessels will need a larger amount of fluid volume to "fill them up" and produce an adequate pressure.

Patients may lose a lot of fluid through sweat, urine, stool, wounds that are leaking, or through bleeding. The word "hemorrhage" means "large amount of blood loss".