Omnipod IOB Question

Type 1 and LADA Parents of Children with Type 1 Diabetes
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So, first the really good news…over the past 7 days, we’ve been able to stay at, or under 250 nearly 100% of the time. We have had 2 spikes over 250, but nothing nearing 300. 95% of the time, over the past week, we’ve been able to stay within 80 - 180 range (which we’re both really excited about.) We’ve made several adjustments, which I’ll list first, before I get to my question.

First, we wanted to get as close to 50/50 basal/bolus, so we increased his basal rates as follows: Between 12AM - 9AM, he gets .05 basal (which we have been suspending via a temp basal preset that decreases basal by 100%, because he was level around 150 during the nights.) Between 9AM - 10PM, we have him on .20 units of basal and from 10PM - 12AM, he’s on .10 units of basal.

Since we increased basal, we needed to decrease bolus, so we increased his I:C to 1:32. This seems to be working out wonderfully. Now our ratios are around 55% Bolus to 45% Basal…a huge improvement over previous weeks and we’re getting the basal/bolus ranges honed in. I’ve moved down my threshold on my CGM from 100 - 200, to 80 - 180, which is the ideal range I want to see him in as much as possible.

We also made another change in creating a temp basal preset that adds an additional 50% more for 3.5 hours after each meal onto whatever his current basal regimen is. This has helped us practically eliminate the spikes. What this “can” cause; however, if we’re not paying attention, is hypoglycemia. So we carefully watch him post-prandial and, after he “levels off” and starts going down, we turn off that temp basal preset. Also, if we see him going below a certain level that we’re comfortable with (under 150), we suspend insulin until the “down arrow, or 45 degree arrow down” stops, then we resume the basal.

So, that’s the changes we’ve made lately and, like I said, I couldn’t be more happy with the results we’re seeing. We are staying between the comfort zone (80 - 180) over 90% of the time.

My question pertains to the IOB with the Omnipod and how the PDM displays things…

Specifically, sometimes, I see an IOB of 0.00 u, but I don’t understand how this could be so, if the basal program indicates .10 u/hr, .05u/hr or .20u/hr? Sometimes I see 0.00 insulin on board, but I don’t understand why because it seems to me that, with any of the above listed basal programs, some insulin should be onboard at all times? I’m thinking perhaps I may just be not understanding perhaps what (if any) basal insulin numbers are displayed on the PDM…I would think they should be though!

Thanks!

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I would check the users’ guide. There was a time when Omnipod only counted correction boluses as it considered prandial insulin as already balanced off with food. I think that’s changed, though. Most pumps will count boluses but not basal insulin. This may be going on with the Omnipod. For me I’d like to see all insulin accounted for in IOB.

TuD has a lot of threads concerning this issue. I have not read them carefully as I only wore the pod for a part of a year. Your doing a fine job getting this thing reeled in.

Is there any reason why you’re using the 50/50 bolus/basal balance as a goal? Just curious.

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The recommendation from this community has been to try and get the basal / bolus ratios as close to 50/50 as possible and, with the limited testing I’ve been doing for the past 2 weeks, it seems to be making this much more manageable. It brings his overall BG down which helps curb the spikes he was getting over 250 from meals. I’d love to know the rationale myself, but it’s what has been recommended on these forums and something I wanted to test myself and, so far, have been having success with getting them within 5 to 10 % of each other.

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What’s most funny to me, and astounding…is that I just re-read what I just wrote and I was like…whaaaaaat? I actually wrote that?? 1 or 2 months ago, what I just wrote would have been a completely different language to me and now I’m speaking it…not fluently, but I’m getting there! lol

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I’ve followed this ratio in me and observed migration from 45/55 to 55/45 and back. I eat lower carb so my basal is greater than my bolus. If you find it useful as a guide and it works for you then that’s great. I think aiming for a precise 50/50 split might be trying.

Yeah, we do like to toss the jargon around!

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Insulin on board only refers to bolus IOB which is helpful to know so you don’t over correct after a meal bolus for example.

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Yeah, 50/50 will happen by chance…I’m definitely not shooting for 50/50…only as close as possible…within 5% - 10% of each other.

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As you likely remember, my daughter uses the OmniPod system. Yep, if there isn’t any active insulin on board from bolusing or correcting, the IOB display says 0.

I may be misunderstanding what you posted, but does you son go under 100 overnight if you don’t suspend the 0.05 units per hour of basal? If not, why are you suspending his basal insulin overnight?

Although a 50/50 basal/bolus split is considered to be “ideal”, in reality it doesn’t work that way for many people. If you are increasing his basal rate to cover post-prandial spikes, that’s an indication that you need to adjust his I:C ratio and the timing of his prebolus, as covering post-prandial spikes is “technically not the job of basal insulin.” But once again, you need to do what works best.

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He WAS dropping under 100 at nights so it’s why we suspended the nighttime basal; HOWEVER, lately, he’s been in the 150’s so I think we will be safe using .05u/hr and see how that goes. We discussed beginning that tonight. The reason we are doing a mealtime basal preset for mealtimes is really to help the basal percentage. That’s really the only reason at this point, but I think I can compensate for that by adjusting one of his 3 basal programs during the day; possibly the afternoon from .2 to .25 because he still rides high there. Maybe even the .10 to .15. We are continuing to refine and tweak as we go (as I’m sure will never stop), but we just moved his I:C up to 1:32 two days ago from 1:30 – it sounds like my best option may be to tweak one or more of his basal programs and decrease his I:C for meals.

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What is the purpose, or intent, of the functionality within the Omnipod system of being able to make the basal presets if not for meal correction and that kind of thing?

I’m not referring to the Basal programs where you set different u/hr for different daytime segments. I’m referring to the “Temp Basal Presets” where you can increase/decrease basal by X% for Y amount of time.

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Temporary basal presets are what I use if I am playing an hour of racquetball or 1.5 hours of social tennis or taking an hour long zumba class. For the most part they’re set amounts of time and fairly consistent reductions of basal insulin for the activities I’m doing.

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But they can also be set to INCREASE basal rates. What would be a situation where that would be done? I am using it as an extra offset for controlling post-prandial spikes, which has two benefits…it helps control BG levels and it helps me use more basal to keep the basal/bolus ratios within 5-10% of each other.

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I honestly don’t do presets for basal increases. Normally if I’m feeling sick - like coming down with a cold or something and my blood sugar is higher than I prefer then I set a temp increase to see if I can combat it that way.

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Increase can be used for sickness or known stressful situation where you know you may need a little more insulin.

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Agreed with everyone that basal presets are for things like sickness, but not sure it’s all that different from just setting a temp basal. I guess it’s convenient if, for instance, you know your kid runs 25% more on his needs when sick and you are forgetting to update that rate.

Also, I’m not totally sure on this, but when you are aiming for a 50/50 split on basal bolus, I would think that ratio would only be relevant (in so far as it’s ever relevant as it’s just a rough guideline), when you are not using basal to do the job of bolus and vice versa. So let’s say you’re setting high temp basals routinely to prevent mealtime spikes – then you’re just using an accounting maneuver – you’re still giving the same amount of insulin for the meal, you’re just tallying it in the basal column. Similarly, if you’re giving low temps to offset an aggressive meal bolus, that’s actually not that your son needs less basal insulin, it’s that some of his meal bolus is being used to cover his base metabolic needs. IN both those scenarios your basal/bolus ratio may work out to 50/50 but I am not sure if it’s fair to say his ratio is truly 50/50 in those cases.

But, I’m realizing more and more that it may not matter anyways. The whole basal/bolus thing is just a convention to make it easier to dose insulin – particularly if your son is on a pump and his basal and bolus insulin is literally the exact same drug administered by the exact same equipment. Really, your kid needs whatever level of insulin he needs at a given time, and you’re just trying to match it as closely as possible using a bunch of different insulin doses that, when added together, more closely mimics his physiologic need for insulin. Perhaps some of the time, that will result in the canonical and desired basal profile that keeps your son flat in the absence of food, and in having carbFs that will bring him back to his starting BG within 4 to 5 hours…but honestly, we’ve not found that to be true.

Seems like whatever you’re doing is working pretty well, so I’d stick with that and just tweak around the edges until things start getting crazy again. Congrats on getting those numbers into line, you’re doing a great job!

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Others have explained that IOB does not consider basal. So any insulin delivery for meal boluses facilitated through a temp basal increase, will not be noted in IOB. To the pump, basal is intended as background insulin exclusively, and does not factor into IOB to be used to assess insulin duration tails.

The calculation of IOB for OmniPod is based upon meal and correction boluses and the insulin duration that you set. It is a simple calculation, and not necessarily an accurate calculation as insulin does not impact blood sugar in a straight line manner, as the calculation assumes. So it is only a guide, although one I find very useful. There was NO IOB calculation at all for OmniPod in the first generation, so what exists now is a huge improvement.

You may find referring to the user guide to better understand the calculation to be useful. Although the math is simplistic, the method of including meal v. correction boluses in not an intuitive one, in my opinion, and therefore I think it’s worth familiarizing yourself with OmniPod’s approach.

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I like that basal insulin is not included in IOB and it makes sense to me because, like you say, basal insulin is not “meant” to correct a high BG caused by inadequate I:C and/or ISF. This helps me keep basal and bolus/correction insulin separate in my mind, which helps me avoid using an increased basal when what I actually need to do is adjust the I:C, ISF, and/or pre-bolus time (or use an extended bolus).

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Does the Omnipod use a simple linear IOB calculation so that it computes an insulin duration of say, 4 hours, at a 25% insulin used every hour? I think both the Animas and Medtronic pumps use a calculus function (non-linear) to calculate IOB.

Back in the '80s and early '90s, before pumps calculated and displayed IOB, I used paper and pencil and just assumed a linear burn-rate of prandial and correction insulin. That worked OK, but if any doses were delivered within the duration of insulin action time of the last dose, then it was just back to swagging for me. I like the IOB calculators, especially when I stack insulin doses, something I do every day.

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You know, I used to agree with you and had no problem with IOB being calculated with basal as the baseline, but with openAPS I often get frustrated with that accounting system. It can often lead to problems like a slowly downward drifting BG that’s never given a chance to rebound and also weird accounting issues that make it tough to figure out if my son will eventually go low/high.

For instance, let’s say you have no IOB but you just had a very high programmed basal rate 20 minutes before – say it jumps from 0.5 units/hr to 0.2 units/hr. In that transition period, the IOB may go from -.2 units (a nonsensical number because you can’t actually have negative 0.2 units of insulin in the body) to .1 units because of an accounting trick. I guess the answer is to have a smoothly transitioning basal profile, but that is such a PITA to program in and make changes to (especially when you have to wrangle a pump attached to a squirmy toddler).

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Yes, OmniPod uses the simple, linear IOB calculation.

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