greater than 30
By these standards, the OP, though only 16, is actually thin, just barely into the normal range
Hypertension can definitely be inherited. One of my friends, though healthy and normal weight
, had it when he was 18. His daughter developed it when she was 18. Both are on lifelong treatment for it.
Losartan is supposed to increase exercise tolerance in adults, but Sian is young, and young girls her age are surprisingly prone to fainting, for some reason.