Dexcom G7

Hi there,
I wear my G7 on my upper arm on the soft tissue under the arm so it doesn’t get knocked - I find it works best there! As far as the readings go - your blood glucose machine measures glucose in your blood whilst the CGM Dexcom is measuring fluid (can’t remember the technical bit!!) so there will be a slight difference.
I find my Dexcom takes a while to recover from low sugars and can read low for a long time- I suggest always testing your blood in these circumstances. Hope this helps!

It measures Interstitial fluid (too many buzz words to keep track of with diabetes now-a-days) which is approx 15-20 minutes behind a blood test.

Some of the CGMs benefit from calibrating (if your software allows it) - I use Libre 2 and xDrip - so can tell it the actual Blood sugars and xDrip adjusts the readings to match.

This adjustment alters through the life of the sensor - initially they suffer from 'insertion trauma' where the skin swells round the new Teflon sensor - as they get to the end of the sensors life-cycle, the body can 'heal' around them, so the readings go a bit high - calibrating at these times helps.

CGMs are not perfect, and but give a good general trend (enough for looping) and a massive leap over peeing in a tube (for those old enough to remember)