My father is almost ninety and is under hypertension treatment how high shd the highest and lowest bp readings be to be safe for him at this point ?

BP in elderly.: We used to think that older people could tolerate higher BP readings ("isolated systolic hypertension of the elderly"), but now we know that their upper limit of acceptable is really just like everyone else - no higher than 140/90, and the lower the better (although too low is not good either). Bringing the top number down to 130 and even 120 would result in lower risk of mortality.