Dexcom 7 Plus Accuracy

Hi all

We are finding that above 12 mmols that dexcom is maybe 3 or 4 mmols out from finger prick reading where as normal and low blood readings are spot on. Does anyone else find this also?


It’s messy and awkward to do calibrations up there (without affecting calibration accuracy by rolling into a sudden “dropping bG” period from the correction which you inevitably did). But you are not going to get accuracy unless you actually give it some calibration data to use at these at these more extreme readings.

Above about 18, it isn’t going to be accurate. But down around 12, you shouldn’t be seeing errors this large- IF you have entered calibrations values around those readings.

It’s important to remember that even blood glucose meter readings are off by a certain percentage. While this isn’t usually a major thing when your sugars are low the higher your sugars get the more off the reading can be and still be considered acceptable. This means that even the blood glucose meters and less accurate at high readings. When you get to the Dexcom it’s trying to give a reading based off a calibration from what isn’t an entirely accurate system anyway so it can have trouble at high blood glucose levels. I work in the other system and am not sure how to convert but I know that when my sugars go above 250 the Dex and meter start to see significant differences, below that I am fine. It just emphasizes the need to check before treating your highs.