How low can blood pressure go before they consider it a health risk?

Question

My blood pressure today was 118/47

Answer 1

I have had blood pressure 70/40 and nobody said anything.

Answer 2

They like the systolic (top number ) to be above 90 and diastolic right around 60-80. Yes the diastolic is low. How was it taken? If it was by machine than don't fret, their not accurate. Go to your local doctors office and tell them you want a blood pressure check. Most offices allow walk ins for that.