@Hertz4319 , @toddbeall
Gentlemen, in the last two messages the separation of CGM to meter has reared its ugly head again. Keep in mind several points:
 the accuracy of CGM-meter is ±20% for values over 80mg/dL according to these two articles from Dexcom:
Dexcom CGM vs Meter accuracy.
Is CGM Accurate:
 the issue of compression lows can also confuse the issue. Additionally, if the safety of CIQ throttles back insulin to a full STOP, G6-CGM takes extra time to re-configure itself, the BG goes up above the starting level of the CGM reported when the compression low began. This adds confusion to the interpretation of data. In the Tandem world all of this is covered with proper training in reading and understanding the data from Tandem’s integrated display software t:Connect.
Here is what I have collected about compression lows including a professional journal article.
BACKGROUND : Compression lows are caused by the person’s body pressing against the mattress, pinning the CGM sensor/transmitter (CGM) between the person’s body and the mattress during sleep. First, the interstitial fluid (IF) is the fluid around body cells. Most of the time IF is in constant motion and exchanged with fluid in the blood vessels call plasma or serum. During this exchange, IF glucose is enriched and cellular waste products are removed from the IF all over the body.
THE PROBLEM : When a person is in sound sleep and is mashing the CGM into the mattress, the IF is also mashed. It is this mashing or compressing of the IF that causes the IF not to exchange as it normally does. Since the cells around the CGM sensor wire continue to consume (eat) the glucose available in the IF of the compressed area around the sensor wire the glucose in the area drops.
OBSERVATION : It is this low reading in the CGM data seen as a nearly level data graph and then a sudden drop in the CGM report of the glucose level that constitutes the COMPRESSION LOW. Because it is a low reported by the CGM brought about by the pressure on the CGM, the term COMPRESSION LOW has been offered in pumping circles. Because the Compression Low is a low glucose only in the area of the CGM, a finger stick performed in response to a LOW alarm will show NORMAL. The variation between the finger stick and the CGM data leads to frustration and bewilderment, believing technology is the source of the error.
The next observation is the blood sugar measured by the CGM will return to a value near where the CGM line was before the drop in CGM value. The near level line, the drop & alarm, the finger stick of different reading, and the return to the near pre-alarm value is the full picture of the COMPRESSION LOW.
To additionally confound the facts, if an insulin pump decreases or stops insulin delivery during the compression low, the CGM report after the LOW may be higher than the CGM reported before the LOW episode.Proceed accordingly.
Here is a link to Susceptibility of Interstitial Continuous Glucose Monitor Performance to Sleeping Position
Stewart, feel free to ask more.