T3c, managing Insulin on Board (IOB)

[Proud to be erratic]

As a T3c my BG behaviour is erratic and I've been advised to gracefully accept that, which I try to do. Thanks to Librre 2 and the Diabox app providing CGM I'm pretty successful at intercepting potential hypos so get a few brief lows and infrequent real hypos (ie confirmed by symptoms and finger pricks). But I really struggle to manage my BG when I'm busy and active - the very time when it's difficult to monitor diligently.

In particular, I understand the principle that during bolus periods I, of course, have insulin on board - doing its stuff! But I have recently read about the circumstances whereby one's body generally behaves unusually, particularly the more insulin that is "on board". It would seem that muscle activity accelerates the use of on board insulin to transfer glucose from the blood stream and either into individual cells or into storage, thereby accelerating the likelihood of rapid falls into hypo territory. This contradicts what might occur from bolus response, if being more sedentary

Does anyone have a bit more knowledge about the IOB process or general experience of managing BG when active?

By active, I mean doing anything short of formal exercise or work-outs. I'm 72, have a good BMI, walk for long periods for leisure and do most of the physical tasks that any able-bodied person would hope to do, such as DIY, gardening and housework. When I know I'm going to have an active day I reduce my bolus for breakfast by up to 50%, once I tried a bit more, and if I delay the start of that active day (ie let most of my bolus dissipate first) then the rest of my day proceeds fairly successfully. But if I start activity shortly after breakfast I rapidly plunge towards low BG and need to 'manage' that by effectively freezing, taking fast glucose, then lower GI carbs. Thereafter the rest of my day becomes evermore erratic and needs constant managing. If events "intervene" - eg today it rained after I'd pre-bolused at a reduced rate to be able to do a heavy garden job that somebody was going to help me with and now, inevitably, I'm heading into hyper land and trying to find indoor jobs to counter that; so still dragged into near full-time managing of my BG!

 

[rebrascora]

For me, following lower carb way of eating helps to reduce the effect of IOB with exercise and activity. Having a protein breakfast like bacon and eggs or an omelette and salad also means a slow trickle of glucose 2 hours after food so if I am going to be active on a morning, having a low carb, high protein breakfast means minimal bolus insulin and then the protein will keep me pretty steady. If I have the same breakfast when I am more sedentary i need to inject bolus insulin 2 hours after eating to cope with the protein release.

Is there any reason why you couldn't just inject more bolus insulin this morning when the weather turned bad to cover the full amount of carbs you ate, rather than trying to burn them off which, whilst admirable, isn't always convenient or possible.

 

[Inka]

When Humalog was first introduced, the guidance leaflet said it might be wise to avoid exercise in the period close to injecting. This was kind of the opposite advice that was given with regular insulin (non-analogue). People often exercised within an hour or two of eating because it helped. Therefore the ‘warning’ about Humalog was given - that you shouldn’t carry on with your normal routine of exercising close to meals/boluses.

I never see that advice given any more, but what you describe above fits with it. So, can you simply delay the start of your activity and have your day proceed more successfully, as you describe?

On the occasions your planned activity has been thwarted by rain and you’ve already had a reduced bolus, you could just add a little extra bolus to account for that. It happens to me all the time (I have children - very unpredictable days). It is frustrating, especially if you’ve stuffed in some extra carbs as well as reducing the bolus, but your only options are trying to burn it off indoors, which can get a bit mad and stressful, or bolus. You can also, of course, do a combination of those two things.

 

[Lucyr]

Why didn’t you just take the other half of the bolus, or reduce your breakfast carbs to half what you’d planned, when you saw the bad weather? Would seem more sensible than eating what you had planned to cover exercise then going high.

 

[helli]

In my experience, it is down to the individual and the type of activity you are doing,
It may not be a rigorous workout but, if you are not used to a gentle stroll, you can be affected by IOB leading to hypo. On the other hand, if you are a marathon running, a gentle stroll won't have any impact.
I am not a marathon runner but do not feel I need to "take it easy" when I have IOB. For example, if I have lunch out, I do not need to worry about walking home straight afterwards.
The great thing about the Libre is I can use it to learn more than the research says for the "average" person on insulin but learn what it does for me. This means some trial and some error but I have my dextrose with me and ready to act.

 

[Proud to be erratic]

For me, following lower carb way of eating helps to reduce the effect of IOB with exercise and activity. Having a protein breakfast like bacon and eggs or an omelette and salad also means a slow trickle of glucose 2 hours after food so if I am going to be active on a morning, having a low carb, high protein breakfast means minimal bolus insulin and then the protein will keep me pretty steady. If I have the same breakfast when I am more sedentary i need to inject bolus insulin 2 hours after eating to cope with the protein release.

Is there any reason why you couldn't just inject more bolus insulin this morning when the weather turned bad to cover the full amount of carbs you ate, rather than trying to burn them off which, whilst admirable, isn't always convenient or possible.

Thank you @rebrascora ,
The low carb route is an option, but I'm not clear if this will really overcome the issue. I'll certainly try this but my goal is to better understand the subtlety of what is going on when IOB is counterintuitively bringing about a crash rather than steady controlling my BG. My wider goal is to reduce the micro-management I'm doing at present and is unsustainable in the longer term. Currently diabetes is managing me, rather than the opposite; and I have in sight a desire to resume travelling and exploring - without having to quietly wait 3 or 4 hours after breakfast before actively starting my day.

This morning's bad weather is more by way of illustrating how events intervene. Yes, in theory I could have topped up my bolus once it was clear between myself and the person coming to help that we would abandon today's plan and try another day. Meanwhile other "events" conspired to make the bolus top up difficult to achieve in practice until c. midday this morning.

 

[Proud to be erratic]

When Humalog was first introduced, the guidance leaflet said it might be wise to avoid exercise in the period close to injecting. This was kind of the opposite advice that was given with regular insulin (non-analogue). People often exercised within an hour or two of eating because it helped. Therefore the ‘warning’ about Humalog was given - that you shouldn’t carry on with your normal routine of exercising close to meals/boluses.

I never see that advice given any more, but what you describe above fits with it. So, can you simply delay the start of your activity and have your day proceed more successfully, as you describe?

On the occasions your planned activity has been thwarted by rain and you’ve already had a reduced bolus, you could just add a little extra bolus to account for that. It happens to me all the time (I have children - very unpredictable days). It is frustrating, especially if you’ve stuffed in some extra carbs as well as reducing the bolus, but your only options are trying to burn it off indoors, which can get a bit mad and stressful, or bolus. You can also, of course, do a combination of those two things.

Thank you @Inka,
Your observation about Humalog is interesting and I need to gain a better understanding about non-analogue insulin.

I'm keen to avoid just 'waiting' and delaying starting my day. I would like to return to a more normal way of living with all the unpredictability that can occur in daily living. Currently I feel diabetes is controlling me more than it should. I know that my pancreatectomy has abruptly changed my world and I'm truly grateful for the outcome, because the alternative was a poor option. But 2 yrs on I need to find a better way of managing daily living - yes my DM will always need some managing; but I can't help thinking if I wasn't retired how would I be able to hold down a job today. Your observation about children and unpredictable days is most helpful - you clearly have found a way of living with DM and unpredictable days. Did you really find that sometimes you just needed to break off from whatever you were doing and take a bolus correction and can I deduce that your pump has somewhat overtaken that aspect?

When our children were young my recollection is that life was full on 7 days a week; on work days I went to a job that demanded being active and responsive in an unstructured way and at weekends the children were constantly 'needy' and rightly so. Even a sunshine and beach holiday with them was far from restful!

Perhaps I still have expectations that need to be better managed!

 

[Proud to be erratic]

Why didn’t you just take the other half of the bolus, or reduce your breakfast carbs to half what you’d planned, when you saw the bad weather? Would seem more sensible than eating what you had planned to cover exercise then going high.

Thanks @Lucyr, inevitably I've oversimplified matters for your enquiring mind. Today's bad weather was just an example of events intervening.

But today specifically I got up, dressed and breakfasted knowing the weather was not ideal but agreed with the person coming to help me that we'd press on with our plan to do the job today. Then we took a rain check at 8am, 9 am and finally at 11 am agreed the plan wasn't going to happen. Yes, I could then have taken a correction bolus but other things then intervened ....

As I've said in an earlier response my goal is to understand better 'what causes what' and thus anticipate and manage my BG more routinely and be able to enjoy flexible (reactive) daily living. I can't sustain in the longer term my current level of micro management of my DM. IOB and its peculiarities is one aspect that I want to grapple with. Are your days very predictable or do you have to plan ahead and anticipate when days might not follow a tight routine? (Perhaps that would have been a better question in starting this thread).

 

[Proud to be erratic]

In my experience, it is down to the individual and the type of activity you are doing,
It may not be a rigorous workout but, if you are not used to a gentle stroll, you can be affected by IOB leading to hypo. On the other hand, if you are a marathon running, a gentle stroll won't have any impact.
I am not a marathon runner but do not feel I need to "take it easy" when I have IOB. For example, if I have lunch out, I do not need to worry about walking home straight afterwards.
The great thing about the Libre is I can use it to learn more than the research says for the "average" person on insulin but learn what it does for me. This means some trial and some error but I have my dextrose with me and ready to act.

Thank you @helli, inevitably some questions, if I may:
So at what threshold do you decide you need to start taking dextrose and are there prior thresholds that you use to take slower carbs?

I'm aware that you have a pump. Do you use just Libre 2 and its singleton upper and lower alarms or do you have a further CGM app that's informing you about changes?

I recall reading elsewhere that you are happy walking on the flat but uphill can challenge you. When that, or a similar, challenge unexpectedly occurs how do you deal with that?

Are you aware of the IOB peculiarity that can trigger an abnormal fall in BG or does that simply not match your experiences?

 

[helli]

My lower target/alarm is set to 4.5 but I don’t blindly treat it because I am at that level. I look at the steepness of the curve. If it is a steep curve, I treat with fast acting carbs. If the slope is shallow or pretty flat, I do not bother with the carbs.
As I have a pump, I do not need to eat slower acting carbs and I have the option to suspend my basal. I often suspend basal for 15 minutes when my levels are lower.
Unless I am doing rigorous activities, I do not make many changes for iob.
I do try to avoid eating and bolusing a couple of hours before a Spin class or gym session.
Woth regard to walking up steep hills on a hike I vary my behaviour depending upon my fitness (when fitter my levels fall) and where the hills are along the route. For example, on a 5 hour hike, I will need food along the way(nothing to do with diabetes, I just feel hungry). If I stop for lunch before attempting a long steep climb, I reduce my bolus. However, if the climb is 2 hours from my last bolus, I will just keep an eye on my levels and treat if needed.
The other thing I find is that exercising to reduce a high does not work for me. If my levels are above 8 or 9 with no IOB, any exercise will cause my levels to rise as my body is stressed.

 

[Inka]

Did you really find that sometimes you just needed to break off from whatever you were doing and take a bolus correction and can I deduce that your pump has somewhat overtaken that aspect?

@Proud to be erratic Sadly my pump isn’t psychic and I still need to tell it to bolus (via my phone). If my blood sugar is slightly high, I often don’t stop to bolus but if it’s higher I do stop, finger-prick and bolus. Of course, this will usually guarantee somebody asking to go for a long walk/play football, etc etc! A pump still needs a lot of input, and doesn’t guarantee great sugars or an easy life. It’s a fair bit of work. Like everything, there are pros and cons.

Regular insulin is often written off by HCPs as “old-fashioned” but they don’t have diabetes and aren’t aware of the benefits. Newer isn’t always better as far as insulin is concerned.

 

[Lucyr]

Thanks @Lucyr, inevitably I've oversimplified matters for your enquiring mind. Today's bad weather was just an example of events intervening.

But today specifically I got up, dressed and breakfasted knowing the weather was not ideal but agreed with the person coming to help me that we'd press on with our plan to do the job today. Then we took a rain check at 8am, 9 am and finally at 11 am agreed the plan wasn't going to happen. Yes, I could then have taken a correction bolus but other things then intervened ....

As I've said in an earlier response my goal is to understand better 'what causes what' and thus anticipate and manage my BG more routinely and be able to enjoy flexible (reactive) daily living. I can't sustain in the longer term my current level of micro management of my DM. IOB and its peculiarities is one aspect that I want to grapple with. Are your days very predictable or do you have to plan ahead and anticipate when days might not follow a tight routine? (Perhaps that would have been a better question in starting this thread).

On days that don’t follow a routine, I just test more and bolus/snack more as needed rather than assuming something will happen. Eg do normal insulin and if the activity ends up going ahead, test and snack during it as needed.

 

[Proud to be erratic]

My lower target/alarm is set to 4.5 but I don’t blindly treat it because I am at that level. I look at the steepness of the curve. If it is a steep curve, I treat with fast acting carbs. If the slope is shallow or pretty flat, I do not bother with the carbs.
As I have a pump, I do not need to eat slower acting carbs and I have the option to suspend my basal. I often suspend basal for 15 minutes when my levels are lower.

Again, many thanks.

Like you, I respond according to the curve trend. And (as is happening right now) I am, fortunately infrequently, completely caught out - I was taking a phone call and not vigilantly monitoring!! Inexplicable why though. Certainly not obvious it has anything to do with IOB.
Does that happen to you with your pump?

Unless I am doing rigorous activities, I do not make many changes for iob.
I do try to avoid eating and bolusing a couple of hours before a Spin class or gym session.

Noted

Woth regard to walking up steep hills on a hike I vary my behaviour depending upon my fitness (when fitter my levels fall) and where the hills are along the route. For example, on a 5 hour hike, I will need food along the way(nothing to do with diabetes, I just feel hungry). If I stop for lunch before attempting a long steep climb, I reduce my bolus.

Typically by what percentage?

However, if the climb is 2 hours from my last bolus, I will just keep an eye on my levels and treat if needed.
The other thing I find is that exercising to reduce a high does not work for me. If my levels are above 8 or 9 with no IOB, any exercise will cause my levels to rise as my body is stressed.

I do get a response from moderate exercise or activity, even when my bolus has expired. Its not immediate, but can be within 30 mins. If the activity is intense then my BG rises at first but later falls quite abruptly. So I had an anaerobic 20 minute walk that I now very infrequently use, because I can't confidently gauge what the consequence will be. I try to keep all my activity as mild or moderate.

 

[Proud to be erratic]

On days that don’t follow a routine, I just test more and bolus/snack more as needed rather than assuming something will happen. Eg do normal insulin and if the activity ends up going ahead, test and snack during it as needed.

So, can I assume from this that your bolus ratios are certain values, perhaps different for times of day, (your normal insulin) and that you don't then apply a reducing adjustment factor for probable or possible activity/exercise?
I have ratios that I use for days when I know I'm going to be inactive and apply a reduction for planned active days - particularly for breakfast pre-bolus. That prebolus factor varies according to what I think I'll be doing that day. In practice, because I'm usually active as a principle, this means I'm routinely applying an adjustment factor which varies a bit. As I write this it seems to me that I could do some sums and reverse my logic - ie use a standard reduced set of ratios and increase the bolus on days when I know I will be inactive or definitely less active. But at the moment I'm doing what I learnt from carb counting and have sort of settled for doing what I know.

 

[trophywench]

You can only find out 'by what percentage' by treating yourself as a Lab rat and trying X or Y percent. No two PWD will ever be exactly the same. So try a percentage and see what happens!

If one or more of the 40+ different things that might affect BG are also putting their oar in - of course just because it did or didn't work this time is no guarantee it either will or won't next time.

Patience is a virtue, find it where you can.
Always in a woman - seldom in a man .......

 

[Proud to be erratic]

You can only find out 'by what percentage' by treating yourself as a Lab rat and trying X or Y percent. No two PWD will ever be exactly the same. So try a percentage and see what happens!

If one or more of the 40+ different things that might affect BG are also putting their oar in - of course just because it did or didn't work this time is no guarantee it either will or won't next time.

Patience is a virtue, find it where you can.
Always in a woman - seldom in a man .......

Thanks @trophywench,
I fully understand the lab rat analogy and indeed this is what I've been doing in a slightly more haphazard way. But I asked that specific question to try and get a better sense of what others do, who aren't on a pump (or before they got their pumps).

Yes the 40+ other factors still apply, although I'm spared at least 7 of the biological factors and potentially a couple of others. But it is still for me, as an uncomplicated Civil Engineer, far too many factors to try and address mathematically. Never mind whether the diabetes fairy is playing or on the touchline on any one day.

But my original reason for posting this thread was to get my mind around the deceptively complex subject of IOB and the somewhat counterintuitive consequence of that.

When you were working and perhaps before you had a pump, were your days very predictable or did you have to plan ahead and anticipate when days might not follow a tight routine? I know that I am new to this, but now 2 yrs in I can't imagine how I could have a full time job with my current level of unsatisfactory BG control. Yet, being T1 doesn't prevent most people from reasonable daily living. Or does it? I'm not expecting this to be easy, but there has to be "tricks or simple solutions" to help.

 

[trophywench]

Couldn't make that much of difference with 1u pens (half unit ones were not allowed for adults at my hospital) so just had to play each and every different situation by ear and carry a 380ml bottle of orange Lucozade (before they reduced the sugar) in my handbag for low BGs - which did happen when we eg decided to walk up a long hill to see what was at the top, that we certainly never planned for - or we go on holiday with friends and someone decides we'll walk along the headland to Old Harry after dinner .... or walk down to the Banks's Arms or Lulworth; the harbour at Honfleur or down to see the fireworks on the beach at New Year in Albufeira etc! A lot of intelligent guesswork - life's too short to make detailed plans for your own time, you keep that planning thing for work and your volunteering activities - not your leisure! (I was an international corporate insurance broker and was both secretary and treasurer of a caravan/camping club with its own site)

It hasn't killed me yet anyway.

Possibly - I dunno? - on Google Scholar, you could try having a look to see what the algorithm is for IOB within the Roche Accu-Chek Expert BG meter? - or for some make of pump which has the Bolus Wizard within the pump itself.

 

[Lucyr]

So, can I assume from this that your bolus ratios are certain values, perhaps different for times of day, (your normal insulin) and that you don't then apply a reducing adjustment factor for probable or possible activity/exercise?
I have ratios that I use for days when I know I'm going to be inactive and apply a reduction for planned active days - particularly for breakfast pre-bolus. That prebolus factor varies according to what I think I'll be doing that day. In practice, because I'm usually active as a principle, this means I'm routinely applying an adjustment factor which varies a bit. As I write this it seems to me that I could do some sums and reverse my logic - ie use a standard reduced set of ratios and increase the bolus on days when I know I will be inactive or definitely less active. But at the moment I'm doing what I learnt from carb counting and have sort of settled for doing what I know.

I use -25% and -50% for certain planned definite activities, eg -50% before swimming, but it was unplanned days you were asking about. I don’t reduce bolus for unplanned days, I just test and adjust more with carbs or insulin as needed.