Answer:
Many things.
Step-by-step explanation:
Blood pressure is a needed thing in a body. It gets blood to your organs and everywhere that needs it. If it didn't work, many things could happen.
Too high BP(hypertension):
If your blood pressure is too high, it can cause ruptured vessels, heart attacks, strokes, heart failure, which is where the heart enlarges too much to continue pumping blood at the adequate pressure/speed, kidney disease/failure, which would be from damage to the arteries around the kidneys, vision loss due to damage to the vessels in the eyes, angina, which is chest pain due to narrowed vessels in the chest, some forms of which may cause heart attacks.
Too low BP(hypotension):
If you're experiencing hypotension, there are many things commonly associated with it. These are dizziness, fainting, nausea, blurred/fading vision, lack of focus, and fatigue. If hypotension becomes extreme, it can cause someone to go into shock, which is life threatening and can and will cause death.