One of the issues here is that though the definition of diabetes seems to be standardised worldwide at a hba1c of 48mmol/L or 6.5%, the level for
prediabetes seems to vary country to country. Also, some countries do it more hba1c, others by fasting blood sugars.
Add in the fact that home meters are only required to have an accuracy of +-15% and a reading of 5.8mmol/L could be anything from 5mmol/L to 6.8mmol/L . (Or outside this range if you have a bad testing strip or contamination on your hands).
Here's a link from this website, so it is referring to UK standards
Normal blood sugar ranges and blood sugar ranges for adults and children with type 1 diabetes, type 2 diabetes and blood sugar ranges to determine diabetes.
www.diabetes.co.uk
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@plantae I'm not sure if the prediabetes levels are the same in Australia as the UK, I know they are not quite the same in New Zealand as the UK. (NZ has prediabetes at 41, while I think the US and Canada start it at 39).
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It seems to me (disclaimer I'm not a doctor) that the whole point of prediabetes is to signify that you are at a higher risk of getting full blown diabetes, so it's not surprising that it's a little arbitrary where the cut off points are.
But I'm not really in a position to comment too much on this, since I was diagnosed T1 as a child, and so have no personal experience of the issue.