Sorry but your second comment has completely baffled me. I’m a newbie remember so no idea what you are talking about.
Is the doc likely to take another blood test tomorrow?
Apologies.
Your blood result of 42 was from a test called an HbA1c, which is an estimated average of your blood sugars over the previous 8-12 weeks.
The readings you’re seeing on the Libre (and that you would get from a glucometer) are one-off blood glucose readings - a snapshot in time, if you like. While the two aren’t directly comparable, there are calculators which estimate what an HbA1c would be based on the blood glucose readings taken day to day. I used one of these which estimates an HbA1c result of 42 to be equivalent to average readings of 7 over time.
I meant it to put your Libre readings into context.
Does that make it any clearer?
The calculator I used was this one:
https://www.diabetes.co.uk/hba1c-to-blood-sugar-level-converter.html
The doctor might take another blood test tomorrow as usually a diagnosis is confirmed by 2 HbA1c tests.
Editing to add more on the Libre incase it was that bit of my second point that wasn’t clear.
The Libre is estimating blood sugars but without using a blood sample! It uses interstitial fluid, so again it’s not a direct comparison to a blood glucose reading using a glucometer. Among other things there’s a time lag between the Libre and blood glucose readings using a glucometer (which is more relevant to someone using insulin). The other factor is that Libre sensors often run high or low compared to readings from a glucometer - those using them will often calibrate for that reason.
It sounds complicated but isn’t once you get used to the terminology.