It is important to realize that teenagers and adults are very much different, which should also make us realize the complicacy involved in the diagnosis of hypertension in teenagers  compared to adult high blood pressure. For adults, it is less complicated as there are numerical guidelines which can be referred for “adult high blood pressure” diagnosis; however in case of a teenager this guideline is void. This is because teens might not face similar risks as adults (for example: heart attack).

The diagnosis of hypertension among teenagers is conducted by referring to statistics stated in percentile. As a reason, AmericanHeartAssociation issued an official guideline for diagnosis. It states that teenagers suffering from Normal Blood Pressure are likely to have their diastolic pressure and the systolic pressure both above the 90th (ninetieth) percentile. Teenagers with preHypertension would possess diastolic or systolic pressures within the ranges of 90th and the 95th percentile.  According the American Heart Association, preHypertension teenager could also have blood pressures above the 120-80 range even though the value may lie below the 90th percentile depending on age. Teenagers suffering from Stage-One Hypertension should have their diastolic or systolic pressures above the 95th percentile along with 5 millimeters-of-Mercury reading greater than 99th percentile.  Teenagers suffering from Stage-Two Hypertension should contain systolic or diastolic (lower) pressures above the 95th percentile and 5 millimeters-of-Mercury.
It can clearly be seen that the guidelines are complicated and hence should be diagnosed only by a doctor.

A certain reading may appear higher while, can actually be normal when adjusted to averages with respect to age. OR it can actually be high while appearing to be normal.