OmniPod Dash PDM Calculator "Error"

I came across this error last night, while making an attempt to combat the tunneling issue, which I admit I have to do more reading on and that I might be going about this the totally wrong way. I’m only a month into pumping after all.

My CF is 1:5 and my i:C is 1:12. I was eating out and allowing myself 71.5g, having looked up the restaurant’s nutrition info. My BG was at 120 (which is my low end for correcting). If I put those numbers into the calculator, I would have had a bolus of 15.65u. So I wanted to split it up into dosages closer to 5u each.

I first put in 20g and my 120 BG to get a 5.65u bolus. I waited until that was delivered and started a second calculation with 25g and 120 BG, and got 5u. It was then that I realized it was already counting the previous bolus as IOB and reducing my calculation accordingly - anti-stacking and all that. But if had done my 3rd segment this way (26.5g and 120 BG), it would have reduced it again and i would have taken a far less units than I wanted/needed.

Moral of the story, you have to use the calculator with everything to calculate your bolus, but then enter each manually to actually get that dose.

Smart to think about the effects of a series of insulin doses affecting the pump bolus calculation.

Is there any reason why you don’t consider just doing one dose but delivering it over 30 or 60 minutes or longer? Different pumps use different terms for this but it’s all the same thing. Extended bolus and square wave bolus are two of those terms.

I checked out the Omnipod Dash User Guide and found this explanation and graphic on page 153.

While the user guide only mentions slow to digest meals as a reason for using an extended bolus, I see no reason why you couldn’t use it to prevent tunneling insulin from leaking out and raising your glucose level.

I have done extended boluses in the past, I just thought that 3 quick successive boluses would get it all on board closer to the timing of a single bolus, compared to pushing it out over time. And i was thinking of it as a pre-bolus too. i may be overthinking. Doing a lot of experiments at this point and having trouble seeing what is working and what’s not. Too many variables - makes my head spin

Are you keeping any written records? I know this is a hassle but you don’t have to do it forever. It’s a great way to keep your thinking clear and it can teach you some things. It can keep you from getting too wrapped up in all the details so that you can see the bigger picture.

In the example you posted about, needing a total of 15.65 units of meal-time insulin, have you successfully dosed three consecutive manual 5 unit doses without any leaking? If you have then maybe you could use the bolus calculator to figure out the dose needed but then abort that process and deliver manually as you describe.

You’re likely a step ahead of my thinking here.

Extended bolus is the way to go, but start small. Deliver slightly more than you originally wanted to, but deliver 90% upfront and 10% over an extended period. You want to be careful because extended bolus can be real aggressive and can drop you like a rock. Use with caution.

One of my fatal flaws has always been recordkeeping. My partners hated my timekeeping when I was practicing law. I’m tracking everything on Sugarmate - my Dex, insulin, carbs, exercise, pod changed, etc.

My other twist is that I have an ileostomy due to colorectal cancer - so no colon. (A) This means low fiber, instead of high, and (B) I’m not sure what happens to indigestible fiber that usually processes in the colon and helps regulate BG levels. So I’m not sure my food/carbohydrate absorption is “normal.” There are certainly graphs of my BG that just don’t make sense to me. Hey, but at least I’m getting neurotic while trying to figure it out :rofl:

Thanks for your suggestions and support

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I’m still in the “teenager” phase - sometimes I think I’m a bit indestructible.

I’ve tried a variety of extended boluses with dinner meals. None have had extreme response. Some seem to keep me flat for a few hours, only to spike a lot later (which then refuse to come down regardless of bolusing).

@The_Burn “My CF is 1:5 and my i:C is 1:12”

Per your next calculations it looks like it is CF 1:12 and I:C is 1:5 (opposite?)

You say at those numbers you would need for 71.5 carbs, you would need 15.65 units of insulin. But for 71.5 carbs you should need about 14.3 units, the difference is the correction of your Bg being 120.

With the first dose it has remembered it already gave you the correction for your 120 BG, it’s not going to do that again.

So 1 unit for every 5 carbs is

At 20g 5.65 units and that includes the correction
At 25g 5.00 units
so the third would be
26.5 g giving you 5.3 units

And that comes to the original 15.65
so it didn’t or wouldn’t have shorted you anything, the correction dose was in the first dose.

Unless I’m missing something???

A ‘few hours’ makes me think the basal, not the bolus, is too low.

When I’m able to keep my dinner BG in check, my basal keeps it right. For example, last week I had a 7-ish-hour line steady around 125-130.

Now dealing with DP is a whole other story - no matter what my basal (& correction boluses), I’m between 150-160 after 1am. I’ve topped out at 2.5u for now as we had set my max basal rate at 3u and I’m waiting to see my Endo next week.

1:00 am doesn’t sound like DP, some people have higher needs at night. But I can tell you for my DP I had 3 times my normal basal dose settings in my pump to combat with DP for about 3 hours for quite a while. It’s finally not nearly so bad although off and on it reminds me it still can be!

I noticed you said you stayed flatlined at 125-130. If your aim is for 125 and you hit 150, that is only a 25 point increase, which isn’t that bad from DP. I can go from my goal of 95 to 175 on a bad DP day, although thank goodness those are much rarer nowadays.

Well, I’m trying to dial in as close to 100 all the time. After being on & off compliant over most of my 9
yrs of T2, and ending up with Stage 3 CKD this past year, I’m really making the effort now. Thank god for CGMs and the OmniPod (since Medicare wont pay for tubed pumps for T2). It makes it much easier. Over my first 5 weeks my estimated A1C is 6.7 and my SD has dropped from over 30 to 22 in the past 2 weeks. I would have been ecstatic with that A1C in the past, but now I want it lower.

As for DP, it’a pretty close to the typical time (2 or 3:00-8:00) and I have very erratic sleep patterns. Though I guess it doesn’t matter - I need to dose to bring it down regardless (and I’ve got room to play - my lowest BG EVER was 80).

My guess is I’ll eventually have to convince my Endo to prescribe U200. My basal is already over 50u/day and I probably will end up several units higher. To get 48hrs out of my Pods, with a 1:5 IC, I’ve got to keep carbs in the double-digits per day. Not horrendous, but harder when you have to eat low fiber also.

I use Humalog U 200 and like it. Originally they thought I would have to change a pod every 2 days so they prescribed it. It turns out I didn’t need to, my insulin dropped to less than half what it was on shots. But I stayed with it as it works good. I use about 55 units a day of insulin (or 27 of the U200.) You just have to be careful at first with the programming, it’s good to have someone that is familiar with that to help get all the numbers changed.

But 6.7 is doing good, it’s not easy changing things fast. I think as you refine your settings it will get better. I find that timing, prebolusing is the key to helping my numbers. I set the timer on my phone to make sure I don’t forget to eat. But DP really does up your average and it’s a very aggravating thing to deal with.

I am similar. Had lots of complication including a kidney transplant. I was out of control for many years. Now I am in control and regularly see BG of 100 and Std Dev of 15. You are doing remarkably well dialing in close to 100 if you have never been under 80. When I have no IOB, I like to stay in the 70s and 80s. Problem is if your CGM says 70s it could be 60s. But I see Dexcom CGM is usually lower readings than blood tests.

@Marie20 - thanks for the supportive comments. I’m the primary cook in the house & I still seldom know what the carbs are going to be until it’s almost on the table. And I never remember to pre-bolus even when I do :smile:. Hopefully I’ll get better at that part


@rcarli - I can’t take credit for misspeaking :slightly_smiling_face: I’m targeting that 100 unicorn and there have been days that I’ve had a good long run between 100-110, but I’ve had lots of days like today where I woke up at 150, and vacillated between 140-150 all day until my dinner correction. I’ve been running below 115 for about 4 hours now and am just waiting to see what the night will bring. I won’t say that being on the G6 has made me more neurotic but Sugarmate stays open on my phone constantly including on my nightstand at night. :rofl:

So if you aim for 100, but you were at 140-150 all day, why??? That is one thing a pump is good at is corrections. Upon first arising I would be taking a correction…?

Yea, 2.5 is heavy duty. I’ve never, personally, gone that high on basal. I wonder what thats about. Where are your other basals sitting throughout the day? Over a unit per hour?

@Marie20 - the $1 million question. Absorption differences? Learning to dial in different correction factors for different times of the day? Haven’t figured it out yet.

@mohe0001 - yep, still making plenty of insulin (c-peptide was 2.01 in December) but obviously very insulin resistant. My long-term insulin increased when they cut my Metformin in half due to CKD. I was on 60u of Toujeo before pumping, and it wasn’t enough (and my boluses were fairly large too). My basal now is all above 2, totaling just above 50u/day. Still last night I went from 114 at 10:30p to a 162 peak at 6:00a. But my mean was 138 & my average was 137. Getting there.


Your an interesting cat. Unusual.