Great point Kenny, Anybody out there who is diagnosed with hypertension based on a single measurement and given meds should fire their MD immediately. -Not only is the true BP variable, but the instruments are also variable, not to mention the environmental factors cited by you. Also, shame on the the AMA and CDC for specifying an exact figure for the "normal" blood pressure (e.g., 120/80 or 115/75). At the least they should add plus or minus 10 for systolic and 5 for diastolic in the calculation, since no precise single measure can possibly be valid. The notion that, e.g., 121 is pre-hypertensive and 120 is normal, applied to any particular reading, is downright silly.