Systolic Blood Pressure High systolic blood pressure is 140 mm Hg or higher. (Normal values are less than 120 mm Hg, and prehypertension levels are between 120 mm Hg and 139¤mm Hg.) Subjects with high blood pressure are encouraged to take action to lower it. A pharmaceutical company develops a new medication designed to lower blood pressure, and tests on 25 subjects result in an average (mean) decrease of 2 mm Hg. Analysis of the results shows that there is a 15% chance of getting such results if the medication has no effect.