I find that readings can and do vary. When first diagnosed I was testing 3 to 4 times a day, now that I have had my 2nd HbA1c test that indicated stability, I am now just testing on alternate days, or when I am eating something totally different.
As an example a few weeks ago I had baked salmon with sweet potato mash and veg, a glass of wine and coffee, my post meal reading was 8, yesterday I had the same meal and the reading was 6.3!
I have made up a database of primarily my main meals, enabling me to see what gives me a spike, this has helped enormously, I now have a 30 day average of 7.3 2 hours post meals.
So far so good😎