Is pre-bolusing an underrated tool in managing diabetes

Although I count carbs before I eat, I wonder if a better understanding of pre-bolusing may be an issue that I could use to better manage my BG. I also wonder if I am one of the few people to ponder this. Maybe this is unknown to many T1D as it was to me.

I recently noticed that lengthening the time between taking a meal bolus and having the meal, reduced the spike in BG from eating. My BG used to go up about 80 points, on average, after eating. Now I take insulin and wait longer before eating and BG only goes up about 40 points.

A few questions:

If you lengthen the pre-bolus time, does that just reduce the interim BK peak or will it actually change you BG end result?

Does anyone have guidelines they use for pre-bolusing?

How important is pre-bolusing in managing you T1 diabetes?


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Pre-bolusing is very effective at reducing post-meal spikes, as you’ve noticed. I pre-bolus as often as I can, though I’m not rigorous about it (I don’t set a timer). Your pre-bolus time will also depend on which short-acting insulin you use, and how quickly the insulin starts to work in you (everyone’s different). I find I need about half an hour with Humalog works well; it was slightly shorter with Fiasp. If you have a CGM and you’re not in a rush, you can bolus, then watch until your CGM starts trending down, then eat. But I find there are many variables. Sometimes my CGM line will start going down 10 minutes after a bolus, but the other day I gave up waiting after 90 minutes.


For us pre-bolusing has been a game changer, we can definitely see the difference in the pattern. We don’t have a specific guideline but we do it based on the bg level and trend shown by the CGM. If my son’s bg is a bit high, we sometimes bolus with up to 40 mins in advance or wait until we see the the trend go down.


Pre-bolusing is great.

However, IMHO it is not appropriate for initial education for newly diagnosed T1s. There is just an overwhelming amount of education required right out of the gate. This is my opinion why this technique is not taught. Often times, there is no follow-up formal education for the “advanced class”.


Perhaps that is where forums like this come into play.

Once somebody is ready to move on, the various advanced techniques are often times best learned from experienced people who actually do this.

All just my opinion.


To the question.

We find pre-bolus to be most effective for breakfast. Other meals not so important.

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Prebolusing is the bomb!

We had a technique of prebolusing for breakfast well in advance and extending the bolus over a half an hour. That seemed counter-intuitive to me, but helped with certain types of food to keep the post meal spike in control without bottoming out later on. It was inconvenient though, so we landed on superbolusing with which we had stupendous results.

For certain meals, prebolusing not only avoids the spike, but can also reduce the amount of insulin needed for the meal for Caleb. Since he’s not “correcting,” he seems to need less insulin. That’s not a scientific conclusion of ours, just a hunch. There are too many variables at play to know for sure.

Prebolusing can be a bad choice for Caleb for some meals. Anything that’s slow to release should not be bolused in advance. I also see that as Caleb has grown, he’s less sensitive to insulin overall, and therefore the beneficial impacts of prebolusing are not as dramatic as they were when he was wee.


There clearly is a benefit to moderating the spike; does anyone think it reduces your later BG level?

Yes. I think it can. For Caleb he needs more insulin to lower a blood sugar. If he’s just maintaining it, he needs less. That was the point I was attempting to make about needed less insulin overall.

First of all, prebolusing is both under-used and under-rated. I find it highly effective at reducing post meal spikes. I use a CGM and watching the trendline post-injection, I learned to “wait for the bend,” a downward trend written about by Dr. Stephen Ponder, author of Sugar Surfing.

I general, I’ve found it takes more insulin to correct a higher glucose level than a lower one. I think a case can be made that given the same insulin dose, comparing one using a pre-bolus with one that does not, that the lack of pre-bolus will leave you at a higher level later. It may not be dramatic and this would be hard to prove given that the same insulin dose delivered in two instances will each have a different array of the many factors that can affect any insulin dose.

I think that pre-bolusing gives you a lot benefit for the effort it takes. The biggest danger is the inevitable distraction that life can throw at you to unintentionally delay your meal too long. Phone alarms can help with this.


Hm. Do you mean, does it result in a trough later on? In an ideal world the insulin tail should coincide with the digestive process and give you a nice low curve and a flat landing, but this is rarely an ideal world. Other factors have a bearing on this too, such as the fat content of your meal. I generally eat LCHF (Low Carb High Fat), but at lunch time I’ll frequently indulge in some carbs–chiefly bread, because sandwiches are just so dang convenient–and sometimes struggle with a late-afternoon spike when the digestion cycle finally gets going. I agree with @Lorraine that it’s much easier to flatten a spike before it gets going than to bring one down after it’s underway, so I do pre-bolus and just try to keep an eye on my CGM for the first indication of a delayed rise 3-4 hours out. Bit tricky to judge how much to bolus for that–it’s really experience based (a.k.a. guesswork).


Agree with Terry4 that probably underused and underrated. I have been T1 for 50 years and never used or understood the benefit. More time should be used educating T1D about this. When I had 200+ BG often frustrated it took add’l bolus and 4 hours to get back down. Used to skip meals too. Now I take the meal and correction bolus and wait 45 min to eat. 200+ comes down fast. I think huge benefit to knowing this.

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I’ve been T1 for coming up on 35 years, and pre-bolusing is relatively new to me too (thanks TuD!). I used to just inject for my carbs and go ahead and eat, figuring the insulin would take care of the carbs and that was it. But that was before I started pumping, and more crucially, before I started using a CGM some years later (was it really only 2015?). The CGM has made pre-bolusing easier, but more importantly it made me MUCH more aware of what my BG was doing all that time between finger sticks, and it wasn’t pretty.

It makes sense that you need your insulin to get into its upward effect curve before hitting it with a wave of carb-driven BG, but no one ever made much point of telling me that. I think partly it’s the old story that the primary concern of the medical professionals is always always always avoiding hypos, and they err on that side time and again. Which make sense from their POV but for those of us who are self-motivated to do better–and have the tools, like CGM, to do it–that isn’t such an overriding concern.


Ditto !!

That’s when I started paying more attention to pre-bolusing.


Pre bolus is one of my best tools in my very large diabetes toolbox. It takes some time to figure out what works for you. I do suggest a John Walsh’s book Using Insulin to help with duration, timing etc.
Pre bolus helps with those darn post meal spikes and as Terry has stated my biggest problem is sometimes I don’t sit down to eat in a timely fashion. I usually set a kitchen timer so I don’t end up low. But once you get a system down, it is a great and easy tool to help level out blood sugars!


I may have a different experience than many here bc of the timing and place of Caleb being diagnosed - 2007 at the age of 3, treated at Yale. We got tips like this as we acclimated to diabetes management. I learned more from online forums like TuD, but Caleb’s care team was able to provide some progressive guidance.

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Lorraine, how old is Caleb now?


I got it 15. Tough especially if he is athletic.


But I bet the “forgetting to eat” is not a common occurance when doing a pre-bolus.
[for a 15 year old boy]

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In the 1960s when I was diagnosed with type 1 diabetes all I can remember about eating meals was sitting at the table holding onto the edge for dear life to keep from falling out of my seat because I always had to generate severe hypoglycemia to compensate in advance for the coming blood sugar spike. As a result, I can’t really remember eating a meal in those days since my consciousness was so dimmed. But this was what it was like in the days of NPH and Clear insulin as the only treatments available.

When I went off to university I decided not to put myself through that anymore.