Is the basal/bolus model the only way to think about insulin dosing?

Type 1 and LADA
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So, I’ve been basal testing (as much as possible with my toddler).

The stars aligned yesterday to finally basal test his mid-morning, early-afternoon as he fell asleep in the car on a long ride.

It became clear immediately that his basal dose, already somewhat small, is too powerful at that time, as it dropped him between 3 and 5 points every 5 minute increment on the Dexcom.

However, this dosing was recommended by his ENDO and he’s on such a small basal dose (about 25 percent of his TDD) and all the books say it should typically be 40 to 55 percent of TDD. On top of that, his dose is so low that I can only drop it by 25%, or perhaps have periods where it’s on/off to mimic the total he needs over a longer period. That would make for a very confusing basal profile prone to error.

At that point my husband wondered whether there’s any strong evidence-based foundation for having a basal profile that keeps you absolutely level at all times? Really, the whole “basal/bolus” model is just that – a model of how the body works with insulin – but not necessarily the only one that could be used.

In my son’s case, my husband argued that his basal is helping pull down his spikes and allowing us to give smaller bolus doses during mealtimes. Since those doses are the biggest source of variability, he was arguing that an admittedly “wrong” basal could still reduce overall variability. It’s true that it’s much easier to treat a slowly down-drifting BG from an overly high basal, rather than a hyper-crash from a big meal that was either carb-counted incorrectly or simply had unpredictable effects.

On the other hand, it’s also possible that the basal has some kind of synergistic effect with the bolus dose and that the crashes are a result of the combination of the two. I’m also wondering whether dropping down his basal doses and then strengthening his CarbFs will result in the same TDD, but with more of a “superbolus” effect – in essence providing a bigger pool of insulin at the beginning of his meal to reduce the spike, while leaving less at the tail end of his eating cycle to drop him low.

Overnight it seems clear we need a stable nighttime basal, but beyond that, I’m struggling to convince my husband that lowering the basal is the right way to go.

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Before abandoning basal/bolus, I would first abandon the idea that basal should be 40 - 55% of TDD. After 42 years of T1D, I frequently do not fit that profile - in part because my activity is so variable from one day to the next.

Could your toddler still be honeymooning and producing enough insulin that his basal needs are extremely low at this time in his life?

I would also point out that a basal profile doesn’t keep you “level” but within a range. For me, I am looking for that range to be between 70 - 150 mg/dl.

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I think basal/bolus theory is an ideal case that helps us understand a way to dose insulin but is not always possible in the real world. Do you think anyone’s insulin needs, non-Ds included, remain the same from day to day? I don’t.

I think that mixing up the basal and bolus functions is very common, even among the best controlled diabetics. The whole point is to get the basal dose close enough so that you can deliver a rational bolus dose and make reasonable analysis from there.

I’m sure you’ve heard that the ideal basal dose will keep the BGs flat without a meal. It counteracts the usual sugar release from the liver and is not intended to metabolize any nutrition.

I’m with @YogaO on the benchmark numbers of basal providing x% of the total daily dose. That might work in the ideal theoretical world but I would not give that assertion any weight.

I don’t think that 1 unit of basal added to 1 unit of bolus produces anything more than 2 units of action. I do think, however, that we’re playing on a dynamic field. You son’s insulin sensitivity probably changes during the day and it may appear than his response to insulin changes.

I don’t want to weigh in on your basal position versus your husband but you could test each hypothesis (more than once is better) and decide from the results.

I think it’s interesting that Sugar Surfing author and T1D, Dr. Stephen Ponder, uses a flat basal for his entire 24-hour day. He gets great results with this as part of his regimen. I’m thinking that the reason that this works for him is not because his actual basal need is flat but because this nominal rate is close enough and his other dosing tactics compensate. Does that make any sense to you?

I think using the dynamic mindset as described by Ponder is helpful. I think I’ve read elsewhere that your son uses a CGM. That, I believe, is essential to employing surfing tactics. Good luck! I think controlling blood sugar in a growing child has to be one of the most difficult challenges in diabetes. Your dedication and love are obvious while your curiosity and intelligence bode well for your son’s future.

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I think the most important thing to realize is that, no matter which approach you choose, T1D does not play by the rules. I don’t mean to sound critical, but I think your expectations of how well you will be able to manage your toddler son’s diabetes are not completely realistic. There are just too many variables involved, and you can do everything exactly the same way and get two very different results. Fine-tuning basal rates and figuring out the best ISF and I:C and DIA and everything else will all help to make things as smooth as they can be. But even if all of these things are optimized, you will still end up with undesirable results a good deal of the time. (And this is especially the case with children, who are constantly growing and whose needs change on an almost daily basis.) You can drive yourself crazy trying to find an answer that simply and unfortunately doesn’t exist, or you can do your best with the tools you currently have available and learn to accept that much more time than you’d like will be spent out of range. I wish I had something more positive to tell you…

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With all due respect, rgcainmd, I totally understand that T1D is inherently unpredictable, but at no point have I articulated that I want perfect or predictable control for my toddler, you seem to be inferring that just based on my question – which was just a very technical question about whether there’s anything sacrosanct about the basal/bolus formulation or whether there’s anything wrong with getting some of the excess basal to cover what ostensibly should be the bolus dose. Basically, I was asking a math question and you are giving me a more metaphysical answer that boils down to: stop trying so hard. How, exactly, does it help someone who is trying to do the best for their kid to tell them not to try?

I just want to do as good as I can. I am also a computational biologist by training so I am inherently interested in the theoretical underpinnings of what we’re doing 80 gazillion times a day, even if it wasn’t my son’s care that was at stake. We are also building an AP for our son, so getting a good understanding and a good foundation is important for us to decide which type of model we want to implement. For instance, while the basal/bolus is what most diabetics are taught, my husband is debating using an algorithm that varies ISF based on prior information, and uses that as essentially the main variable.

I also think doing things systematically will help me deduce what is impossible to aim for given my son’s physiology. For instance, if his carb absorption rate is above a certain threshold with a certain food, then I can virtually guarantee there’s no way he will stay in range when eating it, or know that i can encourage him to graze rather than gobbling it down, or that he has to eat a smaller portion if it’s really critical he needs to stay in range. These are rules of thumb obviously, but just because they don’t work 100 percent of the time (or even 65 percent of the time) does not mean they’re useless.

For the record, my goals are basically this: NOT get him kicked out of daycare because he has more than two hypos a day. Have him in range as much as is possible given his diet and what we’re seeing on a day-to-day basis. Have him reach the A1C targets set out by his endo as realistic.

But most importantly – have a logical and well-formed reason why we are implementing a given plan on any given day – this is particularly important to me because there are two different people treating my son, and we want to know what the other person is doing and not make mistakes based on not knowing what the other person did and why. Already we have had scenarios where my husband upped a basal or ISF ratio without me knowing, and I was using the bolus calculator without realizing that it was a stronger factor, leading to a crash.

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By no means was I telling you not to try. I try every minute of every day to keep my daughter’s numbers within range, and don’t plan on trying any less any time soon. What I’m pointing out is that T1D will never fit as neatly as we’d like into a theoretical framework, no matter how hard we try.

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Generally, I have noticed that my best-controlled days are close to 50/50 on basal/bolus, but I have rarely if ever reached 50/50 exactly. I usually ends up something like 43/57.

Do your testing and find out what’s happening over the whole day (but always start with nighttime basal). Talking to a really experienced endo or CDE would help when analyzing the data. I have found a CDE who is an RN, an exercise specialist and–if that weren’t enough–he’s also Type 1. Oh…and he’s approximately my age and body type. (So find someone who is an expert).

He told me his medical group wants to start a Type 1 support group-- led by him.

I told him, “You’re golden! An RN, CDE and a Type 1? Who wouldn’t want to join that group?”

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Thanks Timbeak48. I have a scheduled followup with a CDE from Integrated Diabetes services. I hope they can help interpret the data! They were the ones pushing for the basal testing, which I agree is important…but it takes a while with a toddler because they have very fixed schedules and getting them to skip meals without upsetting them is…not straightforward.

Terry4, thanks, your insight is helpful. I’m guessing that you’re right, for Dr. Ponder, there is some “slop” in the system, so to speak, and his frequent micro-nudges are just accounting for them. You could basically get the same types of CGM profiles using a hugely broad parameter space with many many variables, so it would be nice if at least one of the variables was somewhat constrained. But for practical purposes (read: Daycare), I really want to avoid hypos during the 9am to 3pm time frame So I feel like keeping a basal profile that’s mostly flat will be helpful with that. It’s possible that just having some subset of variables (ISF, CarbF, DIA and basal) that work well with each other is fine most of the time, but the edge cases are where you’ll end up in trouble.

We’re trying to use a Sugar Surfing mindset some of the time, though it takes a lot of experience and practice. But I find some of the principles really helpful even with little experience. Waiting for the bend alone has helped slash some nasty spikes by 50 to 70 points in the morning.

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The 40 to 55 percent of TDD is a good guideline for the “average” person, but there are a lot of us for various reasons who fit outside that range. I was age 71 when I was put on insulin for the first time. My endo gave me a starting dose of 8 units basal, which he considered to be a conservative dose for my weight and circumstances and expected it would likely need to be bumped up. Instead, I initially had to get up in the night and eat to keep from going hypo. I ended up reducing the dose to just 6 units initially to keep my BG close to level during the night. I’m sensitive to both carbs and insulin, so it turns out that my ideal basal at that point was just 25% of my TDD.

So there is no need to be concerned if your son’s needs don’t match the guidelines.

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You’ve already received some good broader replies, so I’ll try to be brief and to the point. Regarding the question in the title of your post: the basal/bolus model is just a crude attempt to mimic insulin production in non-D individuals. More importantly, the model yields relatively simple “rules” explainable to average medical professionals and average patients (apparently with limited success, but that’s a different topic). In engineering, we try to decouple complex problems into simpler sub-problems. In that sense, the basal/bolus model splits bg control problem into two sub-problems: longer-term, somewhat repeatable patters are dealt with using pre-programmed basal, while shorter-term and less predictable disturbances - meals and a myriad of other factors - are dealt with boluses (which could be done as normal or extended boluses, or temp basals) or carb corrections.

It won’t take long before you learn how to dose insulin for your kid much better than your endo or anyone else in the world for that matter.

I have yet to find a viable reasoning behind this % basal/bolus split recommendation. I’ve never paid any attention to this number.

If needed, I would try the on/off approach. I do not see why this would be any more confusing or prone to error than anything else.

In my opinion, your husband is completely correct and completely wrong at the same time :slight_smile: A basal higher than what is needed in the absence of disturbances can be a very powerful tool in dealing with after-meal spikes. However, such higher basal rates should not be pre-programmed. You may use temp basals instead, but only when you have good reasons to do so. The pre-programmed basal should not drive your kid low (or high) when he is sleeping, or when he is in day care, or any other time. As a side note, you may take a look at my recent post on the subject of bolusing for high protein/fat meals.

I am with you - I’d try to adjust the basal rates the best I can, and then not rush to make daily basal changes - wait for longer-term patterns to emerge (as basal needs do change over time, especially for kids). Use boluses, extended boluses (or temp basals), and carb corrections to deal with meals and other shorter-term daily disturbances.

Best luck to your family!

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