The latest example of this kind of thing was highlighted by a question my wife asked me. And I had no idea. It turns out, test strips are coded because the enzymes used in them to gauge blood glucose can vary greatly from batch to batch. The coding system is a way to calibrate the meter to the particular strength of enzyme in a given batch — the meter is programmed to expect a certain strength depending on the code it is given. Every single box — code What gives?