Definition of low blood pressure

Low blood pressure is officially defined as a systolic blood pressure less than 90 and a diastolic pressure less than 60.

This is often expressed in writing as less than 90/60

It's not always that clear cut. What if the reading is 95/55? What about 88/62?

In reality the judgement is often based on whether the person is otherwise unwell or is symptomatic as a result of their reading. It also depends of course on what the normal is for that person.