What should I know about gauge of my CGM sensor guide needle?

Generally speaking, CGM sensors are flexible wire-like devices that are inserted with a removable guide needle, and as such their size is stated in “gauge,” which is a measure of needle diameter. What you need to know about gauge is that the smaller the number, the larger the bore.

So for instance, blood donation needles are generally a big honking 18 gauge needle, while flu shots are given with a 25 gauge needle, and insulin needles are 30 to 33 gauge. CGMs historically have run from 21 gauge at the large end, down to 26 gauge on the small end. In general, the fatter it is, the more likely it is to hurt going in, but you also have to consider how deep the sensor rests inside of you. A shallow-sitting large gauge sensor may be more comfortable to insert than a smaller diameter but longer-length sensor.