Why do we wait 2 hrs. after eating to test?

[SCAPER]

For those of us who practice strict self-monitoring of BG levels several times each day, why is it we're supposed to test 2 hours after each meal? I've also heard that some people test 1 hr. after meals too. But regardless, my question is; why do we wait?

[fgummett]

The conventional wisdom is that by 2 hours after a meal, a non-Diabetic person's BG will be back down to their pre-meal level -- just what that level should be is a subject of much debate around here -- anyhow it seems to make sense that a 2 hour postprandial reading can give a reasonable measure of how well we are controlling our BGs. But that is not the whole story, as different foods can cause our BG to spike at different times after eating so additional tests at different times, obviously give more of a picture.

[dbaratta]

The conventional wisdom is that by 2 hours after a meal, a non-Diabetic person's BG will be back down to their pre-meal level -- just what that level should be is a subject of much debate around here -- anyhow it seems to make sense that a 2 hour postprandial reading can give a reasonable measure of how well we are controlling our BGs. But that is not the whole story, as different foods can cause our BG to spike at different times after eating so additional tests at different times, obviously give more of a picture.

Really? I was told that 2-hours post is when the BG is at its highest? That is what the diabetes clinic told me.............

[jwags]

I think it is an individual decision. I usually test around 90 minutes. Depending what you eat you may get a spike several hours later. I found that when I eat dreamfields pasta I get great 2 hour numbers but very high 3 and 4 hour numbers. So some time it is good to vary testing times. A non diabetic will return to fasting numbers, 2 hours after. Most D's should aim for 120-140, 2 hours after.

[fgummett]

Really? I was told that 2-hours post is when the BG is at its highest? That is what the diabetes clinic told me.............I said in a person who did not have D :) Realistically for those of us with D, especially if following the ADA recommended carb loading meals, will peak within 1 - 2 hours after meals... but by 2 hours we ought to be heading back down again.

Of course this is a gross generalization as so much depends on what we ate... pizza for example may spike your BG more than 2 hours later. I think the 2 hour test is a standard, consistent time, that is fairly easy to remember, just like the Fasting BG, before meals and before bed.

---

In terms of the non-D, I have this quote from our resident Mad Doctor : At a diabetes technology meeting a few years ago I saw a presentation from some guys who were testing a continuous glucose monitor. It sampled interstitial fluid every 10 or 15 minutes for 3 or 5 days, I don't remember which. When definitely non-diabetic adult subjects (BMI less than 25, FBS less than 100, and a1c less than 6) wore the machine, eating one day in the clinic and one day at home as they wished, 80% of their readings were under 100. That is 20 hours out of 24. So for an hour to an hour and a half after each meal they might be over 100, but by two hours or just a few minutes later they were back under 100. And they were not only under 100, they were under 90 and even under 80.