Type 2 The reason for the 2mmol/L two hour allowance after eating

IanBish

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I know that you/they/someone recommends that for Type 2 diabetics the rise 2 hours after eating should be 2 mmol/L or less.

Firstly, I'm curious as to where this came from. And secondly, is it mainly because it's easy to remember? And thirdly, shouldn't the blood glucose level come down to where it was before eating? Or are we given an allowance for being diabetic? Would a non-diabetic expect to return to baseline after two hours?

I'm just curious, that's all.
 

lovinglife

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Google a lady called Jenny Rhul or blood sugar 101 and find her blog, its a very long time since I’ve been on it but she has some good explanations & links, it’s an American site so you may have to convert, it’s the place I was pointed to when I first joined here nearly 15 years ago, I learnt a lot from her website/blog she also has books on the subjects which is why I can’t post a direct link ;)
 

KennyA

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Hi Ian

As I understand it, the "within 2mmol/mol" bit is a bit vague because of the vagaries of fingerprick testing and its inherent inaccuracy. I don't think of it as a "rise" after 2 hours because you're actually recording the fall from the peak BG that will probably have occurred over an hour previously.

I've found as time has gone on and my system has got used to having less and less glucose from food, that I do indeed come back to pretty much where I started from by two hours. It seems (I'm speculating here) that my insulin resistance has reduced quite a bit - and of course I am on around only 20g carb/day.

As to where the 2/2/2 advice originally comes from - my best guess is the diabetic associations here and in the USA. It doesn't feature in any of the textbooks, which don't seem to be interested in that sort of thing.

The best info I've found on what normal/ non-diabetic BG profiles look like is this study:

https://pmc.ncbi.nlm.nih.gov/articles/PMC7296129/

It's only small but it's really a demonstration/ info gathering exercise. Peak BG post-eating is around the 45 minute mark, with quite a bit of variation: unsurprisingly, higher carb meals produced higher peaks and slower declines: 28% of the group (iirc, all non-diabetic) had one or more "hypo" events on the basis of the CGM reading (which was calibrated daily). Worth reading, and to note that there is not that much dependable info around about what normal BG looks like - so the nighttime hypos recorded for this non-diabetic group came as a bit of a surprise to the researchers.
 

ianf0ster

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One reason is that while aiming for blood glucose to be back down to the level it was before eating, is that BG meters are only required to be + or - 15% accurate 95% of the time.
Thus One could quite possibly get a reading up to 2mmol higher at the 2hrs post prandial time without the actual blood glucose being higher. Consider that perhaps the first reading is 15% lower than actual and the 2nd reading is 15% higher than actual. Then if the actual BG level was 8.0 then the first reading might be as low as 6.8 and the second reading as high as 9.2.

A 2.0 margin is chosen for simplicity.

Likewise, the length of time it takes for the blood glucose of a non-diabetic to return back to the pre-prandial level, depends upon what is eaten and how much is eaten. But the average is thought to be around 2hrs.

As you probably know, Glycaemic Index varies between different people and thus is just a guide as to how high and how quickly a particular food will raise Blood Glucose. Thus there are no fixed quantities/types of foods which are OK for a Type 2 diabetic.
 
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IanBish

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Thanks for the replies. I googled Jenny Rhul's blog, @lovinglife, and I was quite surprised that she said that most normal people are under 5.5 mmol/L two hours after eating, independent of what they eat.
 

lovinglife

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Thanks for the replies. I googled Jenny Rhul's blog, @lovinglife, and I was quite surprised that she said that most normal people are under 5.5 mmol/L two hours after eating, independent of what they eat.
Yes I remember that, I tested it on my hubby at the time and he always seemed to be there or lower no matter what he ate - but I remember him having a big dominoes pizza and he hit 11.2 at 1 hour but was back down at 5 something at 2hrs & 3 &4hrs. This is when I stopped testing at 1 hour because to me it’s normal to go high at that point for anyone and it’s not a spike but a normal reaction to food, 2hrs onwards is what matters (to me anyway)
 

IanBish

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Yes I remember that, I tested it on my hubby at the time and he always seemed to be there or lower no matter what he ate - but I remember him having a big dominoes pizza and he hit 11.2 at 1 hour but was back down at 5 something at 2hrs & 3 &4hrs. This is when I stopped testing at 1 hour because to me it’s normal to go high at that point for anyone and it’s not a spike but a normal reaction to food, 2hrs onwards is what matters (to me anyway)
I'm quite jealous of your hubby and people like him, with good blood glucose control. Those spikes were what concerned me when I first wore a CGM, so I ignore the early ones and take note of the later readings. I'll risk a Domino's (I used to prefer a Papa John's) pizza when I've lost more weight, to see if that makes me any more "normal".
 
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Lamont D

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I think back to my first few months on the site.
We were greeted to @daisy1 welcome post.
It had a meet and greet and how to start low carb and dos and don'ts.
Sensible knowledge from sensible diabetics.
Much like the present lot, who have gained the knowledge from an open minded forum.

I agree with a lot of the answers given, but a big question I wanted to know as a newbie was...
If you test around meals, would there be a difference in the 2mmols rise advice for me?
As my endocrinologist and the great people here, said I must monitor my BG levels, and keep a record in a food diary, for the main reason was, we (me mainly) were on a voyage of discovery. And my results could not be perfect with the glucometer I used over a decade ago.
So, if it was inaccurate, what would be the use of a snapshot finger prick test? I asked.
It's not so much the individual meal tests, pre meal and two hours after.
It is the long term trends, as if on a graph.
If your BG levels are within that range, you also see that your fasting levels (for some) would be lowering.
The later results for the same meal would be nearer to the pre meal by a mmol or such. And if you are lucky, your hba1c on your next bloods will be lower. And you might be able to have more carbs.
Low carb (if done properly to your dietary restrictions) is known to help insulin resistance and not over producing insulin as some do. It also lowers high circulating insulin in the blood.

Somebody mentioned that there are meal and two hours were almost the same, that is because of good meal choices. I get now then, my two hours is lower than my pre meal! I know! We are all different, and our diabetes is different in how we got here.

You use the around meals tests regime, as a benchmark to how you proceed to control the condition.
It gives you the knowledge of which food(s) Is not suitable for you.
You use the trends to see if you're naughty or nice.
You can even use it to see if you can have a treat or not.
The trends of control is the important thing, and the knowledge it gives you.

Learn from it.
 
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Resurgam

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When I was testing I used the 2 hour mark, and first I got help to see how to keep my levels under 8mmol/l at that point, and once I was settled eating the same meals I saw the number sinking down little by little to under 7 or even less by the time I stopped testing.
I assume that by lifting the load, my metabolism recovered, and the numbers showed that happening.
 

Lamont D

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When I was testing I used the 2 hour mark, and first I got help to see how to keep my levels under 8mmol/l at that point, and once I was settled eating the same meals I saw the number sinking down little by little to under 7 or even less by the time I stopped testing.
I assume that by lifting the load, my metabolism recovered, and the numbers showed that happening.
Even though it's only a couple of numbers, there is a trend down.
 
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