SAFE AQ TESTS

All glucometers and test strips sold in the UK have to meet a standard of accuracy of +- 15%. Although there is anecdotal evidence about some meters being more accurate than others, it's impossible for the public to test this.

So yes, taking 2 readings from the same drop of blood will not usually yield the exact same number. Worst case they would vary by 30% (-15% below 'true value' on one test and +15% above on the other test). My first rection was - this is useless!
Except that in practice it isn't useless at all and in fact is invaluable! The alternative is waiting 3 months for an HbA1C test in order to find out if that superfood you have been eating was really good for your T2 Diabetes in your body, or not! A BG glucometer allows you to test individual meals and even individual foods with almost instant feedback, you just have to test them a few times to get a consensus reading of what they do to your diabetes. People can be more carb sensitive in a morning than in the evening or vice versa, so if you are likely to eat the same food at different times of day you may want to test them a few times each at those different times of day.

The important things to remember are:-
1. All carbohydrates digest into glucose (or don't digest at all in the case of fibre)
2. We are all different in genes, gut biome , insulin resistance etc. So what is OK for one person may not be OK for you and vice versa. If you don't test then you don't know. The GI and GL of a food is only a rough guideline.