Hi if my systolic is 140 and diastolic is below 90 , is consider prehypertension ?

Depends: Hypertension is defined as a systolic (upper number) blood pressure >= 140 AND/OR a diastolic (lower number) blood pressure >= 90 usually obtained on at least two separate readings on separate days. Prehypertension is define as a systolic BP of 120-39 and a diastolic BP of 80-89 again on repeated measurements.

Absolutely:IfTypical: Keep in mind: each reading, both systolic & diastolic (by all conventional methods) are actually estimations, read from only a single heart beat/pulse, different 1 each value. Of the 2, systolic reading has far stronger correlation with cardiovascular complications over time. Even stronger: the pulse pressure (difference between the 2); is a function of CO, artery stiffness & aortic valve status.