Determining Your Pre-Bolus

when all of this new and fancy (and overly priced) fast acting insulin came on the market, i was told that now, instead or having to wait 20 minutes after injecting R insulin before our meal, we could inject and eat right away. wow, was that amazing. this took the cruel planning out of everything. now sitting down at a restaurant could be as easy as pie (yes, that pun is intended).

but, the longer i was on Humolog (and then later, Novolog) i was being told that the insulin actually doesn’t start effecting me until 15 minutes after bolusing. that i was supposed to wait between 5 and 10 minutes after injection and eating my meal. and, i was also told that if i were eating a high carb meal, like oatmeal, i should wait about 20 to 30 minutes after bolusing before sitting down with my spoon and my appetite.

now that we have all these CGMs and multiple finger stick testing around, we can find out the best ways for us to bolus and wait before eating.

i used to be on the Dexcom, and i remember others telling me that they pre-bolused depending on the sensor’s downward trend. that they wouldn’t begin eating until the dex showed their BGs trending downward, meaning, i suppose, that the insulin was alive and fruitful in their system. some people (on another D website) said that they would wait up to an hour after bolusing before eating. personally, i would drop dead if i actually waited that long (unless, of course, my BGs were over 300 ). so all of this new info confused me. i understand pre-bolusing for 1/2 hour if my BGs are very high before a meal, but i know also, that we are all different and have different systems in our different D bodies.

i was curious to know your system. how do you pre-bolus and what are your secrets?

There are always a lot of variables. It’s never always the same length of time. It just depends:

  1. What is your BG?
  2. Which direction is your BG going?
  3. How quickly is your BG moving
  4. How well is your insulin working on that particular day?
  5. How active have you been recently?
  6. What is the meal made up of? Is it spikey foods, or more steady, long-releasing foods?
  7. How safe is it to pre-bolus? Are you at a restaurant with questionable service times? Or are you at home with access to food whenever you may need it?
  8. Is dessert planned for after the meal?
  9. IOB?

I think using “formulas” for something like this can be troubling because there are so many variables. So for me, it always depends on all those things (and maybe a few other things I forgot to list).


Ours is a toddler – it is just too hard to predict how much he will eat. So we rarely prebolus. For breakfast we bolus upfront for the full meal as he’s sitting down to eat it. For the rest, we prebolus for about half the meal and then let the artificial pancreas pick up the difference. This usually keeps him from spiking above 200. We could probably reduce some spikes by bolusing more upfront – but then we’d wind up with a lot of boomerang highs after we treat lows resulting from him not eating his food. In the end his control would be the same or worse.

We only prebolus if he’s high before eating. If we prebolus by about 20 to 30 minutes, he goes low about 45 minutes after eating, then goes high later. So we don’t even accomplish the goal of preventing a spike. Not to mention the added risk of a catastrophic low if he doesn’t eat his food or drops it on the floor or something. For really spiky foods, instead of prebolusing we “overbolus” upfront, giving more than he needs initially, then zero temp him.

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Toddler Diabetes should be like Type 0.5.
The management is so obviously different.
We started at age 8 so missed the excitement of Toddler Diabetes.
During initial diagnosis at our (children’s) hospital stay there was at least one Toddler maybe two with us at the same time (also initial diagnose) so we did hear some of that as many of the classes were group classes with all the families on the floor taking part.

i know that there is nothing so good about being dx and living w/ D, but it sounds great that you are 2 wonderful very involved parents. i was not so lucky and am still not with regards to my own parents. after 30+ years with D, my parents still dont understand the difference between T1 and T2. they have never been involved in my D management, and whenever i get mail from them, they include articals from news papers all about the latest treatments for T2. it doesnt matter how many times i tell them i am T1 and what i can do and what wont work for me (like Metaphormin, etc)

now i just laugh it off. my husband is extremely knowledgable and supportive; he even comes with me sometimes to both my endo and my cde. i know that in many ways, my D management thrives with his support :smile: .

all the very best and good luck w/ your child (children? )


Kind of reminds of my friend, who despite being well educated, believes that ALL education that is required will be delivered by the school. And he bears no responsibility to help push the education of his kids. wtf.

How anyone could have a child with T1 or T2 and not educate themselves is beyond me.

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@Chris That’s called denial, big time. He is just blinded to the harm that he’s doing to his kid.

@daisymae I wouldn’t say that DM. I know that I am much healthier having been diagnosed with D than I otherwise would have been.

But I have been very lucky. For us lucky ones managing our diabetes is no more than a minor inconvenience, and having a low is just a good excuse to have a donut :grin:

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i would love to agree with you, but i cant; since my dx, i have done everything possible to keep my D and my A1c in top notch range. i work very hard at it. but, despite my greatest efforts, i have unfortunately gotten the problems that can come to us Ds. i have gastroparisis , i have neuropathy, i have Graves Disease. also, just an offshoot note: i live with severe mental illness and am required to take medications that are contraindicated for PWD. i take an antipsychotic called Clozeril, which causes an elevation of BGs. it takes a lot of work on my part to balance everything.

so, i do understand exactly where you are coming from. i firmly believe that your gratitude is wonderful. i have my own gratitude that there are solutions out there for all of us. its just that i dont feel fortunate about having to live w/ D.


@daisymae Just the fact that you can deal with all of the adversities foisted upon you, and that you have successfully ( at least as far as your swimming is concerned) controlled your bG as well as you have, AND that you have gratitude for your successes proves to me that you are a winner.

I don’t mean to get all ecclesiastical with you, but I firmly believe that the Lord only gives us what we are capable of handling. And it is PWD’s like you who are proof of it.


It’s often been said that Toddler diabetes is an entirely different disease. Nothing about treating a Toddler converts to any other age (except possibly puberty)

in order to avoid living in self-pity, i make something i refer to as a Gratitude List. each day i try to add something new to it. i put it in my back pocket and look at it throughout the day. it keeps me focused on the good things that i have in my life. it helps me to see the healthy and happy things, rather than the glass being 1/2 empty.

i encourage others to give it a try. it brings me peace and serenity. (i think that is one of the reasons i love to swim so much ; it brings me closer to that gratitude.

i know that this is totally off topic, but i couldnt resist putting in my 2 cents. :wink:


@daisymae This type of thinking is never off topic. DM, you are one in a million!


Let’s suppose the BG is near flat, not skyrocketing, not plummeting.

For example BG= 120 at t=0 , I inject my insulin, adding a little extra insulin because the BG is higher than 100.
If I check my BG at t= 15 minutes, and BG is 110, is the pre bolus 15 minutes? (I can see that there could be questions/uncertainties in this scenario because maybe my BG would have drifted to 110 without the insulin.). How large of a change in BG would you want to see for a decent pre bolus? should the BG reach 100?

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As a general rule, if my BG is in target range, I pre-bolus 15 minutes, except for my breakfast meal, for which I pre-bolus 20 minutes. if my BG is high (and depending on how high it is) I will wait, perhaps, 30 minutes and watch my BG start to come down before eating. the most I have ever pre-bolused on rapid active insulin is 1 hour, and that was bc my BG was quite high.

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I think your strategy is sound, but remember the pre-bolus for us is different based on the type of meal. So try your pre-bolus, if it gives you a good result stick with it, if you go to high or low, adjust it for that meal type. We often pre-bolused 45 minutes before some difficult meals.

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I also use my ICRs to bolus for different types of meals. if I am eating a carb heavy meal, I give myself for more insulin than if I am just eating allow carb/ high protein meal. for whatever reason, also, I have a much much greater ISF when I am regularly exercising; so the meal that follows the exercise requires that I change my ICR as well. (I don’t need 1/4 the insulin as otherwise.)

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