When blood flows through the arteries, it exerts pressure to the arterial wall. The pressure experienced by the arterial wall is called blood pressure. The unit of blood pressure is mm of Hg.
A normal blood pressure level is less than 120/80 mmHg. No matter your age, you can take steps each day to keep your blood pressure in a healthy range. The blood pressure should be maintained inside this range if blood pressure is higher, it is called hypertension. If blood pressure is lower it is called hypotension. In both of these cases it is not good for the body or the heart.
Hypertension: Also known as high blood pressure is, by definition, a repeatedly elevated blood pressure exceeding 140 over 90 mmHg -- a systolic pressure above 140 or a diastolic pressure above 90. Chronic hypertension is a "silent" condition that does not have symptoms.High blood pressure is classified in one of several categories — and those designations can influence treatment. Doctors classify blood pressure into four categories: normal, prehypertension (mild), stage 1 (moderate) and stage 2 (severe).
Hypotension is the medical term for low blood pressure (less than 90/60). A blood pressure reading appears as two numbers. The first and higher of the two is a measure of systolic pressure, or the pressure in the arteries when the heart beats and fills them with blood.