Normal blood pressure for both women and men over 20 years of age is 120 or less systolic and 80 or less diastolic, according to the American Heart Association. Prehypertension is 120 to 139 systolic and 80 to 89 diastolic.
Systolic refers to the top number of a blood pressure reading, which measures the pressure in the arteries when the heart contracts, notes the American Heart Association. Diastolic refers to the bottom number of a blood pressure reading and measures when the heart muscle is resting. A blood pressure of 180 or more systolic and 110 or more diastolic requires immediate emergency medical treatment.