Post Prandial Tests

Do you do your post prandial at one hour after eating or at two? I have thought that two was the standard, but if our spike is at one doesn’t that mean that we need to make sure we are under our target at that hour since damage can happen from highs at any point?

I generally choose to test 2 hours after the first bite because most of my meals are mixed: carbs, lean protein, healthy fat, and fiber. But when I eat things that have less fiber and fat, I may test 1 hour after first bite to try to catch the peak.

You may want to try testing at 1 hour and then 2 hours after the same meal just to see when YOU peak. But the peak also depends on things like your starting bg level, how far in front of the first bite you inject/bolus, how quickly you eat, the mix of foods, etc. It’s not a precise science, but as Dave wrote, the more you test, the more you know.

For people with CGMs, there’s lots of data available. For those of us using test strips, ya gotta poke.

I take it two hours after and sometimes 3 hours (I test many times).

We don’t test after meals to “catch the spike” so to speak. Everyone has a spike after eating whether they’re have diabetes or not. My endo and CDE tell me that a rise of up to 50 BG points within and hour after eating is normal for everyone, including non-diabetics.

For people taking insulin the reason for testing 2 hours after eating, as I understand it, is because most fast acting insulin ‘peaks’ in 2 hours. So testing at that time will tell us if the insulin we took before eating was sufficient to help absorb the glucose ingested at that meal. One hour later may show a higher level than two hours later, but it’s not a very meaningful number since the insulin hasn’t had a chance to do its job.

For people taking oral meds the reason for testing 2 hours later rather than one hour later is . . . I don’t know. Maybe it’s just easier to tell everyone to “wait 2 hours.” Or it could simply be that a spike in one hour is normal and only a later reading provides meaningful data.


Thanks for the replies, guys. I test frequently, but don’t get unlimited strips (10 per day) so I want to “test wisely”. My understanding, Terry, was that highs are damaging no matter when they occur, but someone on another board pointed out that it also matters how long the highs last and that a brief high at one hour that is brought down by insulin by two is ok. What do the rest of you think about that?

Also, they pointed out that testing at one hour and then doing a correction based on that number would be risky because there is still significant insulin on board. So maybe that is why two hours is a more commonly used time?

Digestive rates can vary from person to person & also depending on what’s eaten & how much.

Correcting at two hours is risky as well. Rapid acting tends to last for about 4 hours or a bit longer, though the peak is at 1.5-2 hours, so there’s still insulin on board. People on MDIs are generally told to space their meals 4 hours apart for this reason.

I sometimes test at 1 hour & sometimes at 3 hours to get a better idea of how things effect me.

A brief high (depending on how high) that’s brought down quickly can be dealt with by adjusting the time of the dose. Takes a ton of testing & tweaking to figure this out. Might mean taking insulin dose earlier before eating (rather than the typical 15-20 minutes prior) if there a high-highs at 1 hour, but ok at 2 hours.

Zoe, For routine testing what I do is before and 2 hours after. If I am testing my reaction to a new food then so as to get a better idea, I will test before, 1 and 2 hours after. If someone is making a claim about a food such as ‘minimal impact on blood sugars’ I will test 30 min, 1 hour, 1 hr 30 min, and 2 hr, longer if I am not dropping yet.

As Gerri mentioned the digestive rates do vary by person. Another thing to keep in mind is your active insulin time. Correcting too soon will result in insulin stacking and therefore possibly bring on a low. I personally check at 2 hours 45 minutes up to 3 hours depending on what I ate and what type of bolus I used on my pump.

Don’t quote me on this, but isn’t the standard 2 hours because its the (Roughly) half life of novolog? Thus the result will predict a low that could be forthcoming?

It’s not just a question of when we should test and why we should test at that time. The more important question is 'what should we do with the result?"

If you’re on insulin and you test 1 hour after eating, it would not be unusual to see that your blood sugar has risen. Even a non-diabetic might see that. The issue we have to face is whether or not we need to do something about it or not.

How much has it risen? What did you eat? What did you bolus? How much insulin do you have on board? What will you be doing in the next hour or two?

IMHO, being above your target briefly within an hour after eating is not something to be overly concerned about if you’re still within 50 points or so of where you started. If you’re 100 points over, yes, I’d probably take some action. If higher, definitely. Between 50 and 100, it’s a judgment call. I’d probably wait and see. But have a large glass of water, just in case.

If I feel high within an hour after eating, and test high, but my bolus wizard calculates that I don’t need any more insulin, I won’t take any more. Yes, I rely on it to do the math for me, I’m lazy that way.

As for how much to test - as often as you can. Not everyone’s insurance, if they have it, is generous enough to authorize 300 strips/month. Mine is. But as with all things diabetes, YMMV. It never hurts to ask for more, though.

All things being equal, there’s nothing magic about 2 hours. Nor about 1 hour. Nor about 3 hours. It’s helpful for your individual management to set a standard by which to judge your condition so that you can take the action you need to meet your targets. If one hour works for you, great. If 74 minutes works, fine. Just be consistent. The 2 hour standard may be a holdover, but it’s a useful starting point or baseline. After all, you’ve got to start somewhere. There seems to be a baseline carb ratio of 15:1 for starters and which we adjust based on our needs. The same for correction factors, which seems to start at 50:1.


How to test wisely using 10 strips a day? I devised and revised many strategies only to throw in the towel eventually. I have tried very hard and I believe I am not lacking in analytical skills. My bg is just not predictable enough to avoid 200+ with 10 finger pricks a day. My routine is very consistent and on some days my bg was 50 one hour after breakfast and on other days 250, starting out at about the same bg level and eating the same breakfast. I encourage you to fight for more frequent testing. I had no idea that insurance might pay for 600 strips a month until I read Dave’s post. I tortured myself by stretching 10 strips to last one day. I eventually figured out that I could refill my prescription every 24 days. This got me to 12 strips per day, still not enough. Desperation drove me to apply for a CGM. This was my best move ever (other than marrying my wife). Having a continuous bg readout takes a lot of stress out of D management and I was also able to improve my bg control drastically. Try to get a CGM and if this does not work out go for more strips.

It is precisely BECAUSE our bg’s are not predictable that we need to test at all. Hell, if they were predictable we could get away with testing three times a day.

If one has limited access to test strips and no CGMS the best strategy, IMHO, is testing in ‘pairs’. Once before an event - usually a meal - and once after the event. How long after? Two hours is as good a rule of thumb as any, but YMMV, as always.

On my personal scale of best bg testing practices:

Best - CGMS
Better - Unlimited test strips, test in pairs whenever you feel like it.
Good - 10 strips/day (one before and after each of three meals, one for bedtime and one extra pair for another ‘event’ of your choice)
Fair/minimal - 6 strips/day (one before and after each meal)

If one has insurance and can’t get at least 10 strips a day that person needs to get his doctor to go to bat for him. If she won’t, one needs to get a different doctor.

If one has no insurance, talk directly to the meter company about getting into its discounted or free strips program.

(Nice compliment to your wife, btw, Helmut)

In general, ten a day is good for me. I’m luckier, Helmut, that I have more consistent blood sugars and while not always in target, am rarely way high or way low. So the fasting, one before and after 3 meals and bedtime works for me with an average of 2 per day extras when something is amiss. Congrats on your CGM AND on your good marriage!

Not necessarily Michael. Many of us were taught to test 2 hrs after a meal, 30 years ago. None of the analog insulins were around then. Even Type 2s are taught to test at that time, even when they’re not on meds.

Depending on what I eat, my testing makes more sense at 2 & 3 hours, sometimes at 4 when I can still spike when I haven’t spiked before that. Some delayed digestion plays a part, especially at dinner. I’m almost always ok at 1 hour.

Testing, like everything else D, is so individual. I think the key is that if you don’t know what your body does with food, then you don’t know when the right time to test is… for you.

I’m agree with all those who wrote that the “new” insulins work more than two hours and that’s why I test after 2 or 3 sometimes 4. I can be at 220 two hours after meal and at 98 one hour or less after. My Endo who is not the best Endo in the world told me that my Apidra works only 2 hours! it’s not true. I test 10 X per day. My insurance paid only for 6 tests per day.

I’m still thinking about Terry’s comment that what’s important is what we do with the information. Aside from correcting, which I don’t do unless the number is really high, I use the post prandial (in my case two hours) to make judgements as to whether I can eat a certain food or amount of food again, whether my bolus was correct and then every three weeks (one page of numbers) I review how my numbers and how many times I was over target and decide if my I:C ratio needs tweaking.

We do it at 2 hours only because we usually will need to give a small snack to cover some of the IOB so she does not go low later on. To figure out how high you spike, a test one hour after eating would give a true picture. If cgms is working well, we take that reading for the two hour postprandial.