Blood is carried around the body in tubes called blood vessels. On the other hand blood pressure measure takes into account how much blood is passing through your blood vessels. Low blood pressure is bad because there is not enough pressure to provide blood flow to the organs of the body.
Hypotension is the medical term for low blood pressure. Low blood pressure can be a sign of an underlying problem especially in the elderly where it may cause inadequate blood flow to the heart, brain, and other vital organs. A blood pressure reading of 90/60 mmHg or below is generally considered low blood pressure. Infants and children have lower normal readings than adults.