@Abee, @joe, @Dennis, @wadawabbit
Dorie, Joe, & Dennis have given you great information. First things first, welcome to T1N.
I have an additional piece to add to your thoughts. I tested my G6 CGM, a OneTouch Verio Flex, a Tandem t:Slim X2 with Control-IQ software, and a hospital lab in January, 2020 over several days while I was hospitalized following open heart surgery. The OT Verio and the G6 were within expected ranges with the hospital lab, so the OT Verio was only cheched one day. The most exciting piece of information for me and the nursing staff caring for me was the G6 CGM compared to the hospital lab.
Side info: When blood is drawn from a vein like the hospital lab draws, the red blood cells continue to consume the sugar/glucose in the blood until the blood cells are separated from the plasma part of the blood. So, the longer the phlebotomist carries your specimen around making other draws and returns to the lab, the lower the glucose level goes. On the other hand, it takes 15-30 minutes for glucose to make it from the blood stream to the interstitial fluid bathing the body cells and the CGM sensor wire.
Now, THE BOTTOM LINE: I was able to compare, by noting the CGM displayed value, the hospital lab glucose determination with the recorded CGM data on four days. The hospital determination was alway 14 mg/dL lower than the G6 CGM value.
Based on this informal comparison, I am a believer. The medical community reports the G6 CGM is accurate enough for dosing insulin if all of the instructions are followed. I can suggest you do the same research when you have labs drawn at a point of care provider site. Note your CGM, ask to do a simultaneous finger stick when your blood is drawn and make these same comparisons for yourself. Be sure to allow the variation stated by the device manufacturers as you make these personal observations.
Please share with us what you learn. Sharing helps all of us learn.