Many health organization websites display charts that detail blood pressure readings, including MayoClinic.org, Heart.org and MedicineNet.com. Color-coded charts categorize low, normal and hypertension levels of a systolic and diastolic reading. The top number represents the systolic reading, while the bottom denotes the diastolic.
Adopting a healthier lifestyle with exercise and a proper diet is recommended in instances of prehypertension, as detailed by Mayo Clinic. Doctor intervention with the use of medication is warranted at the emergence of stage 1 hypertension. Immediate medical attention is needed in the event of a hypertension crisis that occurs when the systolic reading is higher than 180 millimeters of mercury or the diastolic is more than 110 millimeters, according to the American Heart Association.