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# Absolute Value

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Under Pressure

Credit: Linda Bartlett/NIH
Source: http://commons.wikimedia.org/wiki/File:Nurse_checks_blood_pressure.jpg

If high blood pressure is bad for your health, that means that low blood pressure should be good, right? Not exactly. There’s a normal range for an adult’s blood pressure. Results that are too far above or too far below the normal range can both be unhealthy. To determine whether a patient’s blood pressure reading puts them at risk, doctors use absolute values.

#### Happy Mediums

Blood pressure measurements yield two numbers, the systolic and diastolic pressures. The systolic pressure is the pressure on your blood vessels when your heart is pumping blood. The diastolic pressure is the pressure on your veins when your heart is resting. Doctors will give you your blood pressure reading with the systolic number on top and the diastolic number on the bottom.

Credit: Steven Fruitsmaak

The average healthy blood pressure reading for an adult is $\frac{110}{70}$. The further your blood pressure falls beyond this figure, the more likely you are to experience severe health problems. People with high blood pressure can suffer from heart failure, stroke, or kidney failure. People with low blood pressure often experience fainting, dizziness, and nausea.

Just how high is too high and how low is too low? To determine this, doctors use the absolute value functions $|S-110|$ and $|D-70|$, where $S$ is the patient’s systolic pressure and $D$ is the patient’s diastolic pressure. If the value of either (or both) of these functions is larger than 10, the patient might be at risk.

#### Explore More

Is the patient whose blood pressure is shown in the image above, $\frac{158}{99}$, at risk for heath problems? How about a patient with a blood pressure reading of $\frac{106}{77}$?

1. [1]^ Credit: Linda Bartlett/NIH; Source: http://commons.wikimedia.org/wiki/File:Nurse_checks_blood_pressure.jpg; License: CC BY-NC 3.0