I suppose it could be a mistake, but to be on the safe side, I would insist that it be rechecked. I know that the safe range of potassium levels is very narrow. It is an element of great importance in the regulation of many body functions. I, myself had a lab report of cholesterol and triglycerides that came back dangerously high. The office where I had the lab work done shortly after that incident changed labs that ran their specimens. So it is possible it could be an error, but if it were me, I would have it rechecked.