HBA1C on a monthly basis?

If you are talking about paying privately for it, it's permissible but rather pointless since it isn't going to change much without a reason. The variability on an HbA1C test is said to be around 6%, so it is more accurate than a single finger-prick test, but less useful than a whole series of finger-prick tests.

Because of the 8 -12 weeks lifespan of red blood cells, HbA1C tests are useless for determining the effect on us of different meals, but with 2 finger-prick tests (before and 2hrs after the meal) we get personalised and immediate notification if our latest meal was good for our Blood Glucose control or if it was bad for it.

I would agree with your nurse IF you were just taking RANDOM finger pricks, But for example some factors can cause diabetics to go both quite high and fairly low during the same day much less a whole month! So their HbA1C might look perfect when the truth was that the Blood Glucose was all over the place!

I think if you shifted from a carb-heavy to a low-carb or keto level you might see a change in A1c each month for the first few months. The result is skewed towards the recent month - Bilous and Donnelly reckon that 50% of the A1c value represents the 30 days prior to test, 40% the middle month and only 10% the initial month. And there's an assumption that your red blood cells live for 90 days. If yours live a bit longer, or not as long, all this might shift a bit.

Suppose you go from 500g carbs a day to 20g carbs/day on Jan 1st - you ought to see a "real" change in A1c for a test done at the end of January, because 50% of that test value is derived from your Bg in January.

Equally expect a "real" fall in February, because now 90% of the test value is taken from two low carb months. I wouldn't expect that much of a fall at the end of March, as you've only shifted the final 10% of the result (acceptable test error is 6% so it could cancel out)

I would not expect a significant change from end March at end April, because you're now working with a refreshed set of red blood cells that have never experienced the high BG levels you used to have. And the same would apply in following months.

Thing is, your fingerprick tests will be showing you all that progression anyway. I guess if you want to pay for it, it's your money, but lowering your A1c doesn't make you "not diabetic".

BTW The example above is pretty much my personal experience - I went from diabetic levels in January to low-normal by April. On countback, it's possible I was below the diagnostic threshold by the end of January. I was getting that sort of feedback from my fingerprick tests, and i don't see how taking further A1c tests would have helped or made a difference.