What is normal blood pressure (BP) is not an easy question to answer. Blood flows through our arteries and veins because of the force created by our beating heart. This force presses on our arteries. When we die and our heart stops beating, the force drops to zero and blood stops flowing. No force, no flow. A healthy blood pressure is essential for healthy life. What is normal blood pressure is very difficult to define.

An unequivocal answer that applies to all people in all places and at all times. There is no one hard and fast metric that can be cast in stone. The answer depends on a number of variables, perhaps most notably gender, weight, age and general health. Even when these variables are controlled, blood pressure may vary from one individual to the next.

Blood pressure can also vary widely during the day depending on the level of physical exertion, stress, ambient temperature and a host of other factors. Any one single BP reading is unlikely to be reliable. Several readings should be taken at different times of day, to determine an average level over time. The average or mean arterial pressure (MAP) is likely to be more accurate.

As a broad indication, a blood pressure reading of 120/80 units is generally considered a healthy range for an adult. A MAP of 93 units is often used as a healthy or standard benchmark for an adult. These figures are important and it is useful to spend a little time to understand what they mean.

The figures 120/80 are read as 120-over-80 and the units refer to milliliters of mercury (mm of Hg). These two figures refer to the systolic and the diastolic pressure respectively. The systolic reading is when the heart contracts. By contrast, the diastolic reading is when the heart is relaxed. One milliliter of mercury exerts a pressure of 0.019337 psi (pounds per square) at sea level. Accordingly, a BP of 120-80 equals 2.3-1.5 psi and a MAP reading of 93 mm Hg equals 1.8 psi. High BP (hypertension) is defined as a BP greater than 140-90 (2.7-1.7 psi). Low BP (hypotension) is defined as BP below 90-60 (1.7-1.2 psi).

Unduly high blood pressure is referred to as a condition of hypertension and unduly low blood pressure is referred to as a condition of hypotension. Consistent with the difficulty of shying away from defining a specific point reading as normal, medical advisers usually identify several different levels of abnormally high or low BP. Common categories of hypertension or hypotension include mild, moderate, severe and very severe. BP above 160/100 (moderate hypertension) requires medical treatment. BP above 180/110 (severe hypertension) significantly increases the risk of heart attack, stroke, cardiovascular disease as well as kidney disease. While low BP may result in dizziness, fainting, chronic lethargy or, in severe cases, coma.

In conclusion, what is normal blood pressure is perhaps best thought of as a range rather than a specific point. Persons diagnosed as suffering from high BP are commonly advised to stop smoking, not to eat salty foods, decrease caffeine consumption, exercise more, and to get adequate sleep without oversleeping.

P.S. For you athletes out there, adult athletes typically record a low BP reading of 90-60 which reflects a typical reading for extremely fit individuals.