What is considered high blood pressure for a 20-year-old?

Above 140/90: The blood pressure is considered high when it is persistently above 140/90; however if someone always has a blood pressure that is at 90/60 (without medication), for example and feels fine but start having symptoms (headache, light headed etc...) when the BP goes above the usual 90/60 , it can be considered high blood pressure for this particular person even when the BP does not go above 140/90.

L40/90: Most would agree that a pressure over 140/90 would be high for a 20 year old.