This is an issue between patient and doctor, since multiple factors need to be evaluated. There's no simple numerical answer that can be given online that applies to everyone.
Speaking only for myself (and I stress MYSELF, not others), when my blood pressure drops much below 115 (top number) due to meds I take for it then I start to get a bit woozy. But without blood pressure meds I jump sky-high into dangerous territory (195/165 is typical for me).
My husband, on the other hand, is normally around 120/70, remarkable for a guy about to turn 81. In fact, his entire blood panel is better than mine, so that when our latest doctor first saw it he said: "You're gonna live to be 120!".
To which I impertinently said, sitting there with them: "He's gonna live to 120? Doctor, can I have a second opinion?"
***SMACK*** He always smacks ms! But I love it, we have too much fun for guys our ages.
And I hope he does live to be 120, he's in better shape than I am. Though as I said to our doctor: "But, that means I'll have to be 105 before I'm rid of him!" ***SMACK***