What is to low for blood pressure? Is 90-61 to low?

Healthy. 90/60 is healthy unless you've just been shot. General rule: lower is better. If you're dizzy (a few seconds of dizziness when you first stand up doesn't count), perhaps the BP is bit too low. If the 90/60 is "natural", it's very good. If it's due to BP meds, they could be reduced a bit. Many very healthy young people normally run bps of 90/60. They are often female.