It can be dangerous and can cause kidney failure. Which means that high potassium can be caused by kidney problems, diet, and also lupus. How high is high? It depends, because the body is very good at balancing electrolytes. It will use sodium to balance this. Why are you asking? Are you wondering how high potassium occurs?
I once had a girlfriend that had Addison's disease due to lack of a hormone. She balanced that by consuming a lot of sodium. Sodium is the balancing agent.
Could be a bad lab test too.
That which does not kill us makes us stronger. -Friedrich Nietzsche