Where does the 2.0 mmol/l come from

Widgets said:

Does it come from anywhere 'official',

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I'll hazard a guess its to do with the "normal" reaction to an OGTT 6.0 to 7.8 is roughly a rise of 2 mmol/l after 2 hours.

From here https://www.homerton.nhs.uk/the-glucose-tolerance-test-ogtt-protocol

Some information is 'official' and some seems to be traditional. I think that the 'no more than 2' is the latter. It made sense so got adopted. There is no rule as such. There is no point going low carb and then eating things that push your sugars into the teens etc.

Other traditions have come about over the years. When eating, when do you start counting the two hours? Some say from the first bite, others say when you have finished. I have been to dinners that lasted more than two hours so there is still room for debate. Again there is no actual rule.

Sugar, flour, rice and potatoes are high in carbs so why mention pasta when it is made of flour? Why not if it helps pasta eaters understand what to avoid? Again, no rule, just sense that became adopted on this site.

But I like @bulkbiker reply. It could well have come from there.

Squire Fulwood said:

Other traditions have come about over the years. When eating, when do you start counting the two hours? Some say from the first bite, others say when you have finished. I have been to dinners that lasted more than two hours so there is still room for debate. Again there is no actual rule.

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This.
After many years I've started to test before and after my evening meal, to assess where I am. I do the cooking and so testing before can get in the way, so I test the same time each evening at 18:30 and then as near as 2 hours after I sit down for the eating of. Sunday night meals can take a long time...
It's trends and ball park figures that I watch.
It's going okay.

I would hazard a guess that it originates from here
https://www.bloodsugar101.com/how-to-lower-your-blood-sugar
This was the first site I found after I was diagnosed, in fact I think it was possiblity a link on Jenny Ruhl's original site that lead me to this forum

I’ve always felt that setting a personal max is a better idea. I wouldn’t want to start at 6 and go up to 8. Having said that, of course, it’s critical to understand by how much certain types of food will spike you. But even then, just because something only raises you 1.5 now doesn’t mean it won’t raise you 2.5 a year from now if you keep eating it between now and then. My aim has always been to put in the absolute minimum quantity of glucose irrespective of what the meter says.

I won’t clutter up this thread but will link to another discussion that will hopefully make my point clearer for anyone with a passing interest;

https://www.diabetes.co.uk/forum/threads/eat-to-the-meter-or-play-the-long-game.160371/

@bulkbiker 's explanation is very plausible.
Presumably the 2 hour- time also has it's origin in the OGTT test
(where the diagnostic evolved over time -e.g. The Oral Glucose Tolerance Test: 100 Years Later (nih.gov) to a simple cut-off value at a single time, which makes sense for simple clinical diagnostics, but there is more information in the glucose response curve) .

For me it is a good 'rule of thumb', but I'm currently using Freestyle Libre's and my post-prandial response? "It's complicated"!

I believe it does have its diagnostic values before Hba1c were available, to measure along with a glucometer, levels from an OGTT. Which was used more often than it is now.
This was why, during my first eOGTT, the sister and house doctor didn't have a clue why I went hypo. And didn't know how to treat it.

But as others have said, it can be a personal target levels, along with lifestyle choices.

I imagine that our sensitive blood sugar meters haven't been around long, so measuring the jump in numbers was more difficult.