Does anybody know why it’s usual for people to be taught to test BG 2 hours after eating, when the peak comes at just about an hour after beginning your meal? Surely the 1 hour figure would be more useful

i think peak is inbetween 1 to 2 hour

What peaks one hour after the meal? BG? Insulin? Says who?

The peak for BG may be different from person to person. Two hours may be a compromise number used for a baseline. If one hour is more accurate or useful for some people, they should use one hour. But the only way to know when your peak is, is to test.

For Type 1’s there may be NO peak in one hour or two hours. For me, my BG will keep going up without end if I don’t take some insulin. I use two hours because that’s the estimated peak of my insulin. If I test in one hour I won’t get any useful information.


For me, testing at the 1 hour mark isn’t helpful except to reveal what the maximum bg spike is. My typical post meal pattern is to have the highest spike in bg at about the 1 hour mark and then a significant drop over the following 30 minutes. The 1 hour mark represents the moment when the insulin begins to drop my bg down. Testing at the 1 hour mark won’t tell me how well the insulin is working (yet). I could test at the 90 minute mark because that will give me a good idea whether the dose was enough but usually 2 hours is fine unless I suspect something is not right. The action of insulin can vary a little bit from dose to dose, so testing at 2 hours allows enough time to assess for certain that the dose was enough.

Just to be clear. If I graphed it, my post meal bg would steadily rise for about an hour, then it would significantly drop for 30 minutes, and thereafter it will be kind of flat with small up and down swings within 20 points.

Your typical pattern might be different so if you have not already done so, you should test at different times for your typical meals, including the 1 hour mark, until you have get a clear picture of the timing of your particular pattern. This way whenever you test at any point you will have the right context to assess what it means.

High blood sugars could do damage in our body regardless of when they happen. Personally, (Im a type 2), when I was first diagnosed and my doctor was establishing an appropriate diabetes management for me, the 2 hr post prandial glucose testing after meals was helpful:

  • we wanted to establish what specific foods or meals are doing to my blood sugar.
  • excessive tiredness/feeling sleepy after eating are symptoms of high blood sugars (The normal range blood sugar level 2 hr after eating is less than 140 mg/dL), therefore, it means my bg is not controlled if it deviates higher.
  • We wanted to check to see how well my diabetes medications are working. There are some diabetes medications designed specifically to lower blood sugars after eating.

Actually, you have extended my question.I was asking why 2 hours and not one. By 2 hours, nearly everyone’s BG is falling. The peak of the spike comes at about 75 minutes, so why not then? I personally keep my Bg much lower than 140[7.78]

In those cases where the peak has been tested, it’s always been found at about the one hour mark. Peak BG is important. they now think that spikes are as damaging as consistent highs. By 2 hours, Bg is dropping in pretty much everyone.

I have always held the test guidelines as guidelines …My believe is : there are many factors , why a 2 hour may or not work for a person with diabetes. Emptying of the stomach, other types of diabetes medication one takes , if on insulin , when one delivers the bolus insulin , type of food ( low glycemic/high glycemic ) one consumes .
Looking at Terry’s response , I seem to more or less duplicate , what he is saying .And we keep on learning about ourselves by poking .

It can’t be true that after 2 hours BG is dropping in pretty much everyone - otherwise there would be no diabetics!!

In addition, if everyone, diabetic or not, spikes their BG one hour after eating that means that everyone, diabetic or not, starts to come down afterwards since, by definition, the ‘spike’ is the high point. Again - where are the diabetics if that is true? Therefore, testing one hour after eating tells us nothing except what our BG is at the spike. (See Don’s comment, below) Your BG is going to go up after eating no matter what. If we want to control how high it spikes, we’d want to test in one hour, but otherwise it’s not very useful information.

What we REALLY want to know is whether our BG is coming back down or leveling out to our pre-meal BG. That’s why we test AFTER the spike.

Should it be 15 minutes after the peak? 30 minutes after? 60 minutes after? Discuss among yourselves. YMMV. But if our insulin has a two hour peak, it makes sense to test two hours after we’ve taken it in order to test whether it has had the desired effect - bringing my BG down.

If not, why not? Did I miscalculate my carbs and not take enough? Is the insulin wearing out? Is my infusion site bad? Is my insulin:carb ratio off?

That’s my story and I’m sticking to it.

I should have said that Bg is dropping in pretty much everyone except untreated diabetics.

The 2-hour PP testing is designed to strike a balance between the effective period of your insulin and the time it takes to digest a “normal” meal. Meals higher in carbs and/or higher in protein and fat (along with any alcohol consumption) can have a significant impact on when to perform your PP test.

Humalog, for example, theoretically starts acting in 15 minutes and stays in your body for 2.5 - 3 hours. While the peak may be well in advance of 2 hours, giving a “correction” bolus at 1-hour could likely lead to a low BG a short time later as the original bolus “catches-up”.

You should have this conversation with your endo.

Fair Winds,

Hi Hana, it seems this is the accepted peak point of BG for an average. as with everything else with diabetes, each of us is different, personally when I test a new food to see how I react, I test at 30 min, 60 min, 90 min 120 min if I would still be climbing significantly at that point I would continue to test. This gives me a curve of what I am doing. If I had only done 2 hr, I would not have know that a peach is not my friend, it was a very quik spike and quick fall. as routine, I generally check at an hour.

Least i found I have to test 3 hours after i eat, otherwise ill overcorrect because the insulin hasnt finished dropping my bg… if i test 2 hours in, the insulin will be working but doesnt bring the number down untill 3 hours…

Different people have different peaks… but you always have to worry about when insulin works for you…
Try this…
If you know your I:C ratio… eat a 15g (low/no fat)snack (even a glucose tab would probably work) when you have a decent BG reading, bolus for the 15g… then test 30min, 1hr, 2hr, 3hr and 4hr (even a 5 hour if you havent dropped back to roughly what you started )(you will want to be inactive and lazy when doing this, BUT DONT DO IT AT NIGHT)…

I bet most of you will have different results.
Usually theres only a slight tail for me at the post-3hr mark so I can correct on it without a problem
YMMV… also you might want to put this on a separate sheet of paper and show it to your endo… If your on a pump, sometimes you want to change the insulin action time based on this

I wonder about this too as BG peaks at about 75 minutes. It may be that non-diabetics return to baseline in about that time. Or that the older insulins acted in that time. It doesn’t actually make that much sense.
However, it does rather depend on WHAT you’ve eaten