How low does blood pressure have to be to become an issue?

No set answer: The higher the blood pressure and longer it's there, the more likely there are to be changes. An exam of your fundus (back of your eye) is a sensitive way to detect early damage. Thickening of the heart (lvh), enlargement of the left atrium, protein in the urine, diminished kidney function are later occurrences. Eventually, heart and kidney failure and stroke occur. It takes years to decades.