How long after eating a meal does blood glucose reach its peak and then start declining again?
Looking online, I’m seeing charts implying it happens at 30, 60 or 120 minutes. I don’t know which is true of any.
I always thought it was 60 minutes, and by 2 hours levels were supposed to be near baseline again.
Is there a consensus?
It varies; no single number will be the correct answer. I’m sure that there’s some individual variability, but the primary determinant in an individual is the nature of the meal consumed. Different foods and even differently prepared foods have different glycemic indexes, which is a measure of how quickly they can be converted to glucose. Additionally, fat consumed will slow down the digestion process, and delay the peak. So, for instance, you’ll get a longer curve and a later peak if you eat 4 oz. of mashed potatoes with butter than if you eat just 4 oz. of mashed potatoes, but both of those peaks will be far in advance of the peak from consuming 4 oz of raw potatoes.
I have diabetes.And now I can’t get OP header tune out of my head.
It’s the damn cretic at the end. Nonetheless,
What is the peak of the
post-prand(i)al glu-cose curve
Pic-ture yourself on a
Boat on a ri-ver, with
Tan-ger-ine trees, and
Mar-ma-lade skies
Tangerines and marmalade are terrible for diabetics 
It depends on what you’re eating, among about a bazillion other factors.
T1 diabetic here, with a continuous glucose monitor - that is, a gadget that tracks my blood glucose in real time so I can see the glucose curves all the time.
Of course, a non-diabetic won’t see as many or as great of a curve as a diabetic. From what my docs have said and what I’ve seen myself when my non-T1 husband checks his blood glucose for fun, a normal person’s pancreas keeps up with the glucose curve quite well; his peaks and valleys are nowhere near mine. The highest I’ve seen my husband go is about 160 right after eating an enormous piece of cake; 20 minutes later he was back down in the 100 range. Most of the time we test him he’s between 60-100, regardless of whether he just ate a metric shitpile of candy or not.
For me, I can tell you:
straight simple carbs (sugary stuff, white bread, popcorn, etc) spike me pretty damn fast - within a few minutes of eating.
Add in a little protein or fat makes it go muuuuch longer. Take pizza, for example. Pretty carby, but also pretty fatty. If I take enough insulin to cover a pizza right when I start eating, I’ll end up going low about 45 minutes after eating. Instead, I have to spread out the insulin over an hour to properly catch the curve (insulin pumps will do this for you)
Food that’s relatively balanced between carbs / protein / fat tends to spike about within 1-2 hours of eating, then taper off.
All kinds of other things affect the spike: have I exercised? Sick? Stressed out? Gotten enough sleep? Phase of the moon? Etc etc. It’s maddening.
Also: ZipperJJ: Tangerines aren’t too bad! Those lil’ ones are only 10-12 carbs. I’m with you on the marmelade (or any other jam/jelly product). That stuff is poison!
And this is the crux of why the standard diabetic diet advice is to eat balanced varied meals with some de-emphasis on white carbs vs. the worst-case American diet.
It’s thought that DM co-morbidity damage is generally proportional to the area under the elevated BG vs. time curve. With bonus damage for time spent at extra high BGs.
A balanced carb-light meal keep the total area reasonable and minimizes the bonus damage caused by BG spikes caused in turn by the inrush from carb-only or carb-leading meals that a defective or absent pancreas can’t keep up with.
It also depends on the speed of gastric emptying and bowel transit too. Many diabetics have delayed stomach emptying, known as diabetic gastroparesis. If the food moves out of the stomach more slowly absorption is delayed.