Adjusting I:C ratios - "acceptable" bump after eating

For those of you who (either on pump or MDI) self-adjust your I:C ratios, what do you consider
an "acceptable" increase in BG 1-2 hours after eating, if the carb count is right ? 30 mg/dl, 50-60 ?
when would you increase or decrease the ratio ?

I know there are book values, but I'm looking for what others do in real life.


I don’t think in terms of increase in BG but in terms of post prandial targets. My post prandial target is under 140. I keep hand written records and there are 4 weeks per page. After each four week period I look at the records and if there are a significant number of over target or low numbers I will look at increasing or decreasing the ratio. I don’t expect the numbers to be in target all the time, my diabetes doesn’t work that way - just the majority of the time. I think it’s also important to first determine if the out of range numbers could be caused by incorrect basal rate (if they start going up, for example prior to a meal - or are ok at the two hour mark and then go up later).


Yes, assuming the basal rates are correct…

what time do you measure your post prandial target ? 2 hours, 4 hours ? i.e. is it after all the insulin has done its work ?


The issue is a bit more complex for me. I tend to eat high fat and high fiber meals with about 50-60 net carbs so that my maximum rise is often at 3-4 hours out. I’ll start fiddling with my ratios only if I start ending up over 130-140 at 3-4 hours several days in a row. My 2 hour target on the other hand is around 95 and my major problem in the first couple of hours are lows.


I am a type 2 and I am very strict about my low carb diet. I seek to be reliably under 140 mg/dl 2 hrs after eat. By reliably, I mean perhaps 95% of the time, maybe once a week being over 140 mg/dl and then I don’t want to by much over. My target is to be back to fasting values at 3-4 hours, and usually that means I have risen 20-30 mg/dl at 2 hrs. I don’t test at 1 hr, but I suspect that I am higher and I just don’t care at this point.

You should choose good, attainable targets for yourself as an individual.

I notice that my 2 hour post meal numbers have way more to do with the timing of my insulin dose vs fat/protein content (specifically fat in my case).
CGMS has shown me that if I time my insulin right I will get very little spike at all. Where I notice my I:C ratio might be off is 3-4 hours later. I will then see an rise in the BG if I am off on Carb counting or I:C ratios.

I measure at 2 hours. By four hours, unless you ate something high carb as well as high fat like pizza, you will have hit your peak and come down. So you won’t have any idea how high you spiked. Two hours is an average time for a pp spike, though some people spike closer to 1 1/2 hours.

So you vary the timing of the bolus before you eat ?

I aim to be below 140 two hours after eating, but above 85. I don’t change things with regard to my I:C ratio unless I am consistently above my target by more than 30-40 points. I’ve recently had a really hard time with my midday meals and I am changing my I:C ratio for that time of day. Lunch in particular is problematic, particularly on the days when I’m at work.

Yep. If there is only moderate protein and low fat I bolus 15-20 minutes before hand. If it is moderate protein and fat I will usually bolus 5 minutes to right as I am eating. When it is something like Pizza I will bolus about 60-70% right at the beginning of the meal and extend the other 30-40% over a 2.5 hour period.

This is my argument for profiles/patterns for bolusing too. If you need multiple basal profiles/patterns for different activities/types of days why wouldn’t you need it for bolus too? Not sure how the pump companies missed the mark on this on?

Thanks…I haven’t tried playing with the timing yet…when pre-bolusing 15-20 minutes, do you start dropping much before eating ?

Uh-oh. I use different I:C ratios at different times of day and am about to switch to a pump. Are you saying they won’t accomodate this and I can only put in one ratio ?

This is exactly why 2 hours post prandial dosen’t make sense to evaluate I:C ratios. If you spiked and came back down to where you wanted then the I:C ratio was right and the bolus was mistimed instead of ratios being off. Please someone tell me if my logic is lacking here because I have heard many say the 2 hr PP is how they evaluate their ratios?

No I am saying that if you wanted a profile set up for an active day vs a work day. Right now with MM and Animas (not sure about Omni but I think it is true in their case too) all you can program is for times of day. What if during an active day you need 1:9 at lunch but an inactive day you need 1:7 at lunch. There is no way to pre-program that and just switch “profiles” to “active day” like you can with basal rates…

No, you can definitely put in different I:C ratios on a pump, I have three very different ratios for my three meals.I think what MossDog means is that with basal you can have say “Weekday basals” and “Weekend basals”. Each profile can have multiple different “time zones” but you will switch back and forth from the different profiles for different days (or say an “exercise basal profile”). For I:C ratios, you can definitely put in different ratios for different times a day but you can’t have separate profiles. Mine are set, for example for 1:7 breakfast, 1:8 lunch and 1:21 dinner and they are that every day until I change one. I can’t just switch to a “weekend I:C profile”. But you can certainly override any suggested number. If, for example, I’m having pizza (poor pizza, always the example!) I know I need to add a kick to the amount suggested by that 1:21 I:C. I hope I made that clear and not more confusing!

I like to think of my ‘target’ as no more than 120 as even if I miss, I have a better chance of being in the ballpark.

Yes, that’s clear…thanks everyone.

1 1/4 hours is when I spike. Never knew it till I got my dexcom! It’s down by 2 hours. Mistimed, yes, but I find that even if I pre-bolus by a good 20-30 minutes, I still spike. Frustrating. I believe my I:C ratios and basals are correct.

No not a whole lot but I am mighty close to heading that direction and I have to admit have gotten into some hairy situations e.g. hypoglycemia for an hour or two (mild- 55-60 mg/dl). That is the reason there has to be moderate protein and LOW fat to do this. If I eat such a meal I can expect an almost instantaneous spike so my insulin and the food offset each other well.

A CGMS does wonders for figuring these things out and it is truly rewarding to know you have eaten 150-180 grams of carbs in a day and “flatlined” between 70-125. Just gives me a warm fuzzy feeling thinking about it :slight_smile: I can stay consistently under 150-160 and only that high for a total of an hour or so during the day but 70-125 throughout the entire day is a bit more challenging.