Insulin On Board (IOB)

[Topher]

Can anybody help about how to work this out. I am on MDI, and the Bolus last between 4-5 hours in my system. If i eat a snack 3 hours after lunch etc, how do i know exactly how much insulin to give myself to avoid stacking - i hope this make sense - Thanks in advance

 

[Spiker]

Can anybody help about how to work this out. I am on MDI, and the Bolus last between 4-5 hours in my system. If i eat a snack 3 hours after lunch etc, how do i know exactly how much insulin to give myself to avoid stacking - i hope this make sense - Thanks in advance

If you are taking insulin for food then there is no risk of stacking and no serious reason to avoid stacking. Stacking is only a serous issue when doing correction doses. So for example the IOB adjustment on my Vibe pump is not used for bolus doses, only for correction doses.

Miraculously sent via Diabetes Forum App. Probably on the 4th or 5th try :-/

 

[Robinredbreast]

Can anybody help about how to work this out. I am on MDI, and the Bolus last between 4-5 hours in my system. If i eat a snack 3 hours after lunch etc, how do i know exactly how much insulin to give myself to avoid stacking - i hope this make sense - Thanks in advance

Hi I understand what you mean and I think spiker has given a good reply. Wish I could add something, but I have never snacked in between meals, just keep to the 3 meals a day Take care

 

[Topher]

ok, thanks for that,

 

[iHs]

If you google 'accounting for unused insulin' click on the top link that opens a pdf file. It explains what I think you are asking about.

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[Spiker]

Basically if you are bolusing for carbs, you inject or dose according to your carb ratio. Regardless of whether that happens once every 5 hours or twenty times in one hour, you don't change the amount you inject or dose for a given amount of carbs eaten.

 

[iHs]

I do

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[Topher]

Ok guys thanks for clearing all that up and thanks for the help. So from what I gather IOB on really matters if you are taking corrections, and if so how does it work as sometimes I might take a correction then have something to eat 1 or 2 hours later, ?


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[Spiker]

I do

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Really? I don't. I sit there and eat snacks say 3gch each and dose for each one at a time every few minutes on my pump and I don't go low. If I did I would assume my basal rate vs carb ratio was wrong, and fix that. How does it work for you?

 

[iHs]

The Vibe's basal rate adjustment jumps a bit so to get round it, one hour delivers more basal and the next hr delivers less plus my carb ratio is 1 to 8g so if I eat a pudding, I will bolus but deliver less insulin to stop the stack

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[ConradJ]

Really? I don't. I sit there and eat snacks say 3gch each and dose for each one at a time every few minutes on my pump and I don't go low. If I did I would assume my basal rate vs carb ratio was wrong, and fix that. How does it work for you?

Just as my basal rate changes throughout the day, my I:C ratio varies according to the time of day. At breakfast it's currently 1:13, whereas at 10pm it's 1:10, irrespective of what I'm eating. These ratios have all changed as my weight has shifted, upped my activity, etc., etc.

 

[Spiker]

Just as my basal rate changes throughout the day, my I:C ratio varies according to the time of day. At breakfast it's currently 1:13, whereas at 10pm it's 1:10, irrespective of what I'm eating. These ratios have all changed as my weight has shifted, upped my activity, etc., etc.

Ah ok. I really must do some tests to see if my ratios vary during the day even after getting my basal pattern just right. I've never noticed it, but then I've never really gone looking for it either.

Miraculously sent via Diabetes Forum App. Probably on the 4th or 5th try :-/

 

[Spiker]

The Vibe's basal rate adjustment jumps a bit so to get round it, one hour delivers more basal and the next hr delivers less plus my carb ratio is 1 to 8g so if I eat a pudding, I will bolus but deliver less insulin to stop the stack

Sent from the Diabetes Forum App

As the Vibe only delivers to the nearest 0.05u I do have to be conscious of rounding errors if dosing for lots of small snacks separately.

 

[AlexMBrennan]

Ok guys thanks for clearing all that up and thanks for the help. So from what I gather IOB on really matters if you are taking corrections, and if so how does it work as sometimes I might take a correction then have something to eat 1 or 2 hours later, ?


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After having measured your BG, and worked out how much IOB is left (e.g. Assuming that 25% of insulin is used per hour) you'd estimate where your BG will end up after all the IOB has done it's work using your correction factor (e.g. You'd need more of a correction dose if you have 15 mmol/l 4h after the last meal compared to 1h).

The point of this exercise is to allow you to correct a high without having to wait for all your insulin to be used up first.

If you are just bolusing for another meal then you'd typically assume that you got the initial bolus right, I.e. that the IOB cancels out the measured BG increase.

 

[CarbsRok]

I found this explanation http://www.diabetesnet.com/about-diabetes/insulin/insulin-action-time/duration-insulin-action even though it's aimed at pumpers you might find it useful )
There are also meters available that calculate IOB, insulin on board etc. So I'm sure someone can recommend one to you or ask your dsn for one

 

[mopsy21]

Hi. I'm on MDI and was told not to bolus for any snack up to 10g carbs. Any rise in bg would show up in the bg reading for the next meal and be corrected then. I use the Accu-chek Aviva Expert meter, which works out how much insulin to take for my meal, according to how much I'm planning to eat. It also takes into account the bg reading. For example, it will suggest more insulin if my reading is around 7/8 (if the snack is close to the meal!) than if the reading is around 5 - 6.

I generally don't have any snacks above 10g carbs, but if I do have something more than that, I would take a bolus for it using my usual ratio of 1 unit for 10g carbs. However, I would still bolus according to the bg reading/meter advice at the next meal. I don't regard this as insulin stacking, because I'm using up some of the insulin by eating. It seems to work for me in that I've had no sudden lows after doing this, and the bg readings are back where they should be by bedtime. I would agree that Novorapid seems to last for 4-5 hours.

I hope this makes sense. I should add that I was diagnosed (T1) about 18 mths ago, and no mention was made of taking correction doses outside of mealtimes. The view was that things would work out by the time of the next meal. I was given the Expert meter from the start, so I don't know if any others will do a similar job of calculating insulin according to food intake/bg level.

 

[Spiker]

The point to remember if attempting to calculate IOB yourself is that it's not a straight line 20%/hr over 5 hrs or 25%/hr over 4 hrs. It is a curve. There will be comparatively little action in the first and last hour. I would not feel confident and safe estimating IOB myself. Even my Vibe pump which uses a curve function is only an approximation.

 

[Spiker]

Yes DAFNE advises no bolus below 10g carbs. This is one of the rules that makes the least sense to me. It seems to be pandering to needle - phobia. On DAFNE I can have 5 x 9gch snacks and bolus no insulin for 45gch. On DAFNE I can have a carb ratio of 1u:2gch and bolus no insulin for a snack that should be 4.5u of bolus insulin. DAFNE is simplistic but this is one of the most poorly thought out aspects. It would be much better if they had said "calculate the dose and if it's less than 1u, don't bother". But DAFNE also assumes we are arithmetic - phobic, or just plain innumerate. :-(

 

[mopsy21]

I haven't done a DAFNE course, but I do see what you mean, Spiker. Personally, I wouldn't have that many snacks, but I must admit I don't want to bolus for just one finger of KitKat in mid morning - it's not needle phobia, but more that my basal insulin can deal with it until the next meal. However, I would bolus if I had all four fingers in one go! Again, it's my personal experience with the Expert meter, but if I put in 20g carbs at tea time and my bg is less than 6.8, the meter will suggest just one unit of QA, so I get a 'free' 10g carbs anyway. If the bg is above 6.8, then the meter says two units. It would be different for someone on a different ratio though; I'm on 1unit for 10g carbs, which hasn't changed since diagnosis.

I agree the advice of 'no bolus for up to 10g carbs' is rather simplistic, but I think when I was told this, there was an assumption that a snack would only be taken, say, mid morning and/or mid afternoon. To be honest, since carb counting and matching QA to the amount I'm eating, I've found snacks aren't strictly necessary anyway!

Coming to T1 rather late in the day (I'm 58), I'm grateful that the Expert meter does the calculations that many people had to do themselves; I have nothing but admiration for anyone who had to do that, or indeed still does.

 

[Spiker]

Can you set the wizard in the Expert meter to recommend by half units instead of only whole units? Half unit pens are easily available. Pumps of course can dose to 0.05u accuracy. So there is less of the "free carbs" due to a rounding error on the wizard.