Hello,
This is Dr. Klarida Papaqako answering your question.
Normal Blood pressure levels are those of 120/80.
Low blood pressure does not get treated if it does not cause symptoms. But also, some people can have levels of Blood pressure almost 90/50 and still not have symptoms, and yet we don't to treat it. So the symptoms are the indicator to tell us when to go to the ER.
The elderly are particularly affected, especially those who have
high blood pressure or autonomic nervous system dysfunction. They may have most frequently symptoms.
Look for
dizziness,
lightheadedness or sudden drops in blood pressure which most commonly occur in someone who's rising from a lying down or sitting position to standing.
So to summarize the answer of your question, I would recommend to go to the ER, or consider treating/finding the cause of low blood pressure with your doctor, when the blood pressure below 120/80 is associated with symptoms mentioned above.
Hope the information helps.
Take care.