Systolic BP vs. Diastolic

According to the American Heart Association, blood pressure (BP) is the measurement of the force of blood against the walls of the arteries as the heart contracts. Two numbers make up a blood pressure reading, the first is the systolic and the second is the diastolic.

Blood Pressure Test

• Blood pressure is measured using a pressure cuff wrapped around the upper arm, while seated, with the arm slightly bent and resting on a table. Millimeters of mercury (mmHg) is the unit of measurement, and is written using two numbers either as 120 over 80 or 120/80.

Systolic

• Systolic BP is the first number of a blood pressure reading, and it measures arterial pressure during heart contractions.

Diastolic

• Diastolic BP is the second number of a blood pressure reading. It measures arterial pressure between contractions.

Blood Pressure Readings

• American Heart Association guidelines indicate that blood pressure readings below 120/80 are normal. Systolic readings between 120 and 139, or diastolic readings between 80 and 89 are “prehypertension" levels. Readings of 140/90 or higher indicate high blood pressure.

Risks of High Blood Pressure

• High blood pressure left untreated can lead to stroke, kidney failure, heart failure and heart attack.

Risk of Low Blood Pressure

• Low blood pressure typically indicates the presence of an underlying illness such as an infection, gland disorders and dehydration.