Blood pressure readings usually fall into four classifications — normal (below 120/80), prehypertension (below 139/89), stage 1 hypertension (below 159/99) and stage 2 hypertension (above 160/100), according to the Mayo Clinic. The levels are used to determine a course of treatment or check one's overall circulatory health.
In a blood pressure check, the top reading in millimeters of mercury or mmHg is called the systolic reading, while the bottom number is the diastolic number. Any number below a systolic reading of 120 and below a diastolic reading of 80 is considered normal, according to the Mayo Clinic.
The Mayo Clinic states that prehypertension is indicated if the systolic reading is 120 to 139 and the diastolic reading is 80 to 89, while Stage 1 hypertension is defined by a systolic reading of 140 to 159 and a diastolic reading of 90 to 99. Any systolic reading over 160 and diastolic number above 100 indicates that the patient is suffering from high blood pressure or stage 2 hypertension.
Healthline defines the systolic reading as the amount of pressure in the arteries when the heart muscle contracts, while the diastolic number references the amount of pressure present between beats.