Freestyle libre reading vs lab result

I have the Libre3 and have found the GMI values to be roughly inline with my A1C results. And my doctor claims that it's usually the case. As someone else suggested, the A1C is a three-month "average". So, to get a similar value, you must look at the GMI computed across three months of data. The 7-day, 14-day, or 30-day values will not be good estimates of your A1C.
And contrary to what other posters have read, I find the Libre3 very helpful with my type 2. It has been very helpful it showing me which foods are problematic/helpful as well as how exercise helps. Getting the immediate feedback has been great in helping me drive down my A1C far faster than would have been possible with an occasional finger prick.

@rjones404 Welcome to Mayo Clinic Connect. I assume you are diabetic and are looking for information comparing continual glucose monitoring (CGM) results with lab results. Did I get that right? I use a Dexcom G6 (CGM) and an old fashioned glucometer for monitoring my glucose levels. At the start it was explained to me that lab levels and glucometers measure blood sugar. A CGM measures the sugar in the interstitial fluid of wherever the device is inserted. Any method can help track how you are doing overall. The lab level requires a lab and is a one time result. The glucometer level is also a one time result but you can have a glucometer at home and repeat the test as needed. The CGM is a 24/7 level that you wear on you. All these methods’ results can be converted to 3 month average picture of what is going on. That is a test called the glycosylated hemoglobin (HbA1C or A1C). What glucose monitoring methods are you currently using?

Mine is always higher than the finger stick blood test

I find it varies by sensor. Some are “good” (read a bit low) and some are “bad”. Still good for trends though.

My sensor is always lower than finger stick blood, usually about 20 mg lower. Annoying when low sensor alarm sounds in middle of the night & I am actually in range. Do use for trends but cost is steep to see just trends.

Nor can I.

5-10 % margin of error with any reading. I do not have any problem with it.

The Glucose Management Indicator on my Freestyle Libre 3 usually runs slightly lower than my actual A1c. But it's close enough, and I don't mind mentally adding a half percentage point in order to "calibrate" it. Day-to-day readings can vary a few points up or down, but so can various meters vary with each other. I can easily check how close my CGM reading is with my BG meter by doing a quick fingerstick test. My Libre been a tremendous help to me over many years, now. I consider it essential for dosing insulin, and only pay a little over $80 out-of-pocket for two 14-day sensors every 28 days at Walgreens.

I can buy a LIBRE sensor for $38 for 14 days. I am not on insulin and I don’t ever want to be either . Insurance won’t cover it for me since I’m not an insulin user, but it does give me valuable information so it’s worth the cost . So I use the monitor to see what foods set off bad reactions. I definitely see how changes in your diet can improve your overall diabetic health and this is one tool to help you get there.

I have used the Libre 3 for about a year now and find it always seems to run higher than my actual readingsI put it on the back of my arm's switching sides every month,example lunch 150 but blood stick test 130-135 usually...but not all the time,90 day GMI on the sensor app.is 6.1 and recent lab work results were A1C of 5.6