Insulin on Board

Has anyone noticed that Insulin on Board is not subtracted uniformly on the Animas. If you are below target, the total insulin on board is subtracted from a correction bolus and/or a carb bolus. However if you are above target, the insulin on board is not subtracted from the carb part of the bolus, only from the BG correction part of the bolus. This seems dangerous to me. If you had taken a large correction bolus say an hour before a meal, the Insulin on Board is still working to lower the Blood glucose. If this insulin is not subtracted from the meal bolus, then too much insulin would be delivered. For example if you needed 8 units to cover a meal and you had 5 units Insulin on board, it woulod recommend 2.8 units if you were say 94 BG. If you are at say 106, it would only subtratc out the BG correction from he 5 units IOB and recommend a bolus of 8 units. I think this is dangerous. With the Deltec Cozmo this calculation was straightforward and would always subtract out insulin on board.

Animas is my first pump so I don’t have experience with other pumps. I personally like how the IOB is handled because I don’t want it subtracted from my carbs. Even if my BS is below target, I know that I need x amount of insulin to cover my meal. If I am low, I will have some glucose to bring me up but I don’t deduct the insulin or I would go really high. In my mind, Animas does it the right way by only deducting it from correction boluses.

Here is an article Gary Scheiner did about IOB in different pumps. Animas actually does it better the the Omni Pod!

http://www.diatribe.us/issues/22/thinking-like-a-pancreas.php

A better explanation is in the following web site whish is from John Walsh of Pumping insulin fame. Note his closing comments "Those in good control (and anyone in certain situations) are likely to receive excess boluses from some pumps when bolus recommendations es are followed.
When recommended boluses are taken as directed, unexplained hypoglycemia can result."

The powerpoint presentation is in a link at the bottom of the page in Bolus on Board Presentation

I still think this is dangerous and everyone should be aware! Careful when you have large Insulin on Board and you may want to adjust the Animas recommendation - Mini Med is even worse!!!!

I too like how the Animas pump calculates insulin on board. I also have always taken full amounts of insulin for carbs eaten irregardless of insulin on board even on MDI. It has never been a problem for me in terms of causing hypoglycemia. Of course since that’s how I’ve always done things my insulin to carb ratio, sensitivity, and duration are set up to give me the right bolus dosages according to how Animas calculates the dose. There are times I will override the bolus calculator’s dosages but this is not one of them. Although I can understand why some would disagree with this.

I’m the same way, Kelly. If I am low, I have learned that it works for me to just take the insulin and eat right away instead of waiting 15-20 minutes as I usually do. I have the same experience that if I cut the insulin by more than a tad, I will go high; I still need my full carb bolus.

I’m just a newcomer to the pump, but I have found I basically ignore the additions and subtractions if I am at “a reasonable number” and go right to the “see result” for the carb bolus. If I am high before my meal than I factor in a correction. It seems to work for me.

On the other hand, I’m so used to doing my own math that I knew I’d have “control issues” with the pump…lol

I’ve always found the IOB correction to work. For some reason I think it works better using the ezcarb function than the ezbg. The ezbg seems to calculate too much insulin so I usually do 10 pts less than what it suggests. For instance, if it says I need 5 units then I do 4.90. I guess with the ezcarb, I am actually eating something so it works differently? I had to adjust my ISF a couple times which also made a difference.

It generally works fine, the place where it does not work is when you are slightly above target BG and have large IOB values say from a recent correction bolus. It thinks that that insulin on board is working on food that was already consumed. I do find it strange that the calculations for a BG value of 94 vs 96 could vary by say 5 units and all should be aware of that. The animas formula treats the insulin on board differently if you are at target or below target.

I haven’t noticed but I do noticed that it will say IOB 0.00. I dont get that! I always thought IOB was always there.

If it has been longer than the duration of your insulin, then there will be no insulin on board. The insulin on board is the remaining portion of a bolus. IOB does not include basal insulin. So say you had a problem with an indusion set that was blocked. You put in a new infusion set and take a correction bolus of 6 units

90 minutes later, wour blood sugar is say 120. and you are going to eat a lunch that needs 5 units. The Animus IOB calculator will show 4Units IOB but will show a recommended dose of 5 units. If you take the full 5 units in this situation within a couple hours, you will likely be very low. If your BG was 99, it would subtract the 4 units IOB from the dose of 5 and recommend a correct dose of 1 unit

oh thank you! I start officially on insulin tomorrow. I know that you have a certain amount going in every hour and thought that would be listed but nope. Still learning the pump

Amy, they might not have your duration set yet. If that is not sent, then you won’t see an IOB.

thanks Kelly! I am still not use to IOB as on shots, you dont know how much is left over.

Your hourly rate of basal will show on the first screen of both the pump and the meter/remote, Amy. Didn’t you used to figure out IOB for corrections when you were on shots? At least now you don’t have to do all the math! It’s really the same thing your pump does. Once you set the duration it’s just math. Like I have mine set to three hours. I know if I take 3 units (to make it easy) at 1PM, at 2PM 2 of those units are left and at 3PM 1 of those units are left. Even if someone else is suggesting the numbers, if you plug them in yourself then you know where the pump “comes up with” all the numbers.

Dick, I disagree with your statement at theend that it would recommend a correct dose of 1 unit. I am not disagreeing with that is what the pump would recommend but I disagree with it being the correct dose. I don’t subtract IOB for my carbs. It is not something I did on MDI and it is not something I do on the pump. If my BS is below target and Animas suggests taking less insulin because of IOB, I take the full amount because that is what works for me. Not everyone would go low like you say. I know that I don’t.

If you recently ate, the IOB calculation to not subtract IOB is accurate; However if the IOB is from a correction bolus and you have not eaten, there are no carbs to absorb the insulin and there is a strong likelyhood of going low, Even John Walsh, author of Pumping Insulin agrees with this. We each have to do what works for us, but I found that the cozmo calculation to work better for me so now I have to do the math in my head!

I agree with alot of what John Walsh says, but I don’t agree with everything he says. I do what works for me and like I said, I did not subtract it on MDI so I like how Animas calculates it.

To me, the way Animas does it makes sense. Like you, I had a Cozmo, and (for whatever reason) I had more lows using the Cozmo thatn I’ve had with the Anmas Ping.



If your BG’s are low, and you’re going to bolus for a meal, then you want to deduct any IOB from what you bolus for new carbs, to ensure that you don’t go low.



If your BG’s are HIGH, and you still have IOB (even if you ate two hours ago) you STILL need to take the full amount of insulin to cover your “new” carbs, since they will run your (stlll high) BG up even more. ALSO… the IOB is constantly decreasing, so I don’t see how you (the pump, actually) could accurately predict how much of your IOB to deduct from the “new” insulin you are going to take.

ALSO… the IOB is constantly decreasing, so I don’t see how you (the pump, actually) could accurately predict how much of your IOB to deduct from the “new” insulin you are going to take.



I totally agree with this. Simply too many factors involved for the pump to accurately determine whether it would be appropriate or not. Pumps are still imperfect so they do require reasoned logic from the user like dickengl states he does the math. I find myself “doing the math” frequently and I have used the Animas, Medtronic, and Omni pumps __> they all have their own faults as far as IOB.

If you had taken a large correction bolus say an hour before a meal, the Insulin on Board is still working to lower the Blood glucose. If this insulin is not subtracted from the meal bolus, then too much insulin would be delivered.



My suggestion if this is often the case for you is to take a look to see if your correction factor is accurate or not. If the correction factor is correct this would be very unlikely to happen very often unless of course you had some sugar on your finger when you determined that you needed this large correction bolus :slight_smile:

Yes but the formula is different if your target is say 100 if you are at 99 and have 3 IOB ve 101 w 3 IOB it will give you 3 more units insulin at 101 than at 99 - that makes no sense whatso ever - Just a word to the wise check and rationalize for your self if the IOB should be subtracted or not.