Experiment: basal vs bolus corrections

Do you have to use more insulin when using bolus vs. basal?

The question is not really proper, since each serves its own purpose. But, ever since we have been involved with diabetes, we have heard the thought, never proven I think, that bolusing requires a lot more insulin than basal to accomplish the same effect. In fact, a recent thread on FUD discussed this very issue in passing.

My son and I have been wondering about the magnitude of the effect, if any. So, a few nights ago ( the night of Sept 8), we decided on an experiment after treating a big afternoon high: we decided that we would leave the night’s basal too low by 5% for 12 hours without eating in that period (so as not to trouble the waters with extraneous carbs and dosing).

That night (around 10pm) basal was set at 0.90 U/hr, although we knew that we needed +5%. We were back in range from our powerful afternoon high around midnight. We had dosed 10U at 3:48pm, with a DIA of 5.5 hours, although, with such a large correction, we saw some insulin tail until 9:30m. We tuned the BG with small corrections of 0.5U at 10:21 and 10:58pm. We felt certain to be outside DIA by midnight.

In order to control the upward creep we had to inject boluses every so often:

  • 1.8U at 1:02am
  • 2.25U at 5:28am
  • 1.5U at 8:57am
  • 0.5U at 10:43am, at which time we increased basal by +5%

Shortly afterwards, we had a late breakfast, that was slightly underdosed. The basal appeared to be properly adjusted until about 3:45pm (establishing that +5% was indeed the right basal) when we dosed for a late lunch.

If we assume that the last basal change was effective around noon, this means that, for a period of 12 hours, we used 6.05U in bolus corrections, where we would have used 12* 0.9U * 0.05 = 0.54U in basal over the same period of time.

Therefore, we used about 6U of bolus corrections to make up about 0.55U of basal, over a period of 12 hours, a ratio of approximately 10:1 for us, for that day.

When I have a computer properly set up, I will post the BG curve. I am still fighting to set up my new MacBook :-).


Fantastic experiment! It is near and dear to my heart!! Thanks for sharing!


To tell the truth, I am not sure if we proved anything with only one sample. Our version of diabetes is rarely very repeatable :slight_smile: But it would be interesting to see if others get similar results.


Sticky hormone highs behave similarly. Very hard to get the basal dialed in just right bc 5% too little can leave me throwing correction boluses at it all day long…but 5% too much can lead to some dramatic surprises if I don’t know that I’m taking too much…or if my needs drop suddenly.

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I don’t think you proved anything, but you have put out a tantalizing hypothesis. What do you think would happen if you went over by 5% on basal?

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That is easy because unfortunately we do it often:-) we go down and down, and have to drink milk every hour to 2 hours.

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Btw, this is quite an interesting question, because I did not have the answer 9 months ago: we were accustomed to making +/-10% changes. But, over the past 6 months, we have started using finer adjustments. In fact, there are times when we end up being in between two 5% increments: one is a bit too high while the other one is a bit too low. In that case, we need to use sugar or insulin, but not very frequently: it may take 4 hours or more before we need a correction.

Still, in that case it would be nice to have a finer adjustment than we do! The Tandem pump has that ability, but the Omnipod doesn’t.

Another interesting question is when to use 5 vs 10% adjustment. When we make a decision to adjust, we look at the slope of the up or down curve. When it is severe, and when the corrections are tightly following each other, we use 10 rather than 5. But that is a qualitative judgment, one that is hard to explain or justify :frowning:

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The Women’s Health category has collected additional work and experience on this topic. :wink: The more, the merrier!

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Testing that today. Against better judgment. Went with a little extra Levemir last night and this morning, thinking it was going to make for an easier day. I wish I could remember WHAT I was thinking, as I throw back my 8th banana…

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If your carbs catch up with you today, be careful with correction doses. A little goes a long way when carrying extra basal. And be careful with meal doses and prebolusing. If I’m running extra basal, I reduce my meal doses by up to 50% depending on what I’ve seen it do that day.


We have also noticed the same thing: if we are trending slightly down, we need to reduce corrections a lot and food boluses some (and vice versa for consistently trending slightly up).


oh wow! that’s a lot of potassium. I looked into the notion that bananas are good for post athletic workout because of the minerals. It turned out that grapefruits are good too. Watermelon brings my sugar up very quickly.


I also don’t want to hijack the thread, but this might explain something I saw repeatedly in Auto Mode on the 670G. I actually have begun referring to it as a “slow roast” because it honestly has a different feel.

In general, over the course of the night, Auto Mode slows down people’s delivery rate in order to help them achieve a flat line. In doing so, it is able to produce an amazing overnight effect, which really is the 670G’s claim to fame. However, the way in which it is doing it creates its own problem heading into the morning… and sometimes even deeper into the day. I have spent a lot of mornings adding up my micro boluses received overnight and, by averaging them, have found consistently to have received an overall reduction of as much as 25-35% of my normal basal rate…sometimes over the span of 6-8 hours. When this is the case, the rebound I experience into the morning and very early afternoon is significant and requires a waging of war, not just a correction, to bring it back down. It’s a correction on another level. I see, time and time again, people, unaware of the reduction, become convinced they have a problem with their infusion set; they become convinced they’re not getting insulin. There are lots of set changes occurring on the tail end of such nights, and it’s been very hard to explain to people why it’s not just the pockets of minimum delivery (which is a suspend that can occur for up to 2.5 hours) that are to blame, but the overall reduction in rate.

Maybe I’m trying to put things together that don’t belong, but when you mentioned that 10:1 ratio, it felt like it explained so much, and that was a result of a mere 5% reduction.

I have a busy day that has begun without me, but until I hear otherwise, you’ve given me some material to work with as I go about it. Thank you for doing the experiment, for having a child who is willing to partake in such an experiment, and for taking the time to report on the experiment. I hope your Friday is pleasant and uneventful, if that’s what you’re hoping for in a Friday. :smiley:


2 posts were split to a new topic: Omnipod: how to set up temp basal as units rather than percentages

As you have discovered, if you reduce your basal, any carbs you eat will have a much greater effect than normal!

I turned my basal down to 65% last night, for the entire night. Still dropped low. Then a small bit of juice - which would normally not do much - spiked me right up!

Is this what you are describing?

The big advantage I had was in knowing I was at 65% all night. It wasn’t the man behind the curtain doing it without telling me. :grinning:


I don’t know… maybe not!

Yes, this much I know, but is this why that rise is crazy? I did know that mixing in carbs definitely added to the problem, but I understood @Michel to be talking specifically about the weight of one insulin versus the other. Maybe I did apply it incorrectly… ??

On that, I absolutely agree. It’s the not knowing if that really makes handling it difficult. It’s working so hard to keep me in the dark… maybe I should stop asking questions and let it do it’s job. :thinking:

You turned your insulin down to 65% all night?? How do you prevent the rise then??

And a light bulb turns on! :zap:


I have to say that if your basal rate is set properly, suspending when trending down works beautifully for us on openAPS. I can’t imagine Tandem’s setup is performing less well. Anecdotally I’ve heard some very good things about it on various parent’s listservs – which is interesting because Medtronic has had its own version of this suspend on low technology for a while now and I never heard it being spoken of so glowingly.

I think to really separate the two you really can’t be comparing pumped basal insulin to pumped bolus. It’s the same insulin going into the same site, just at different rates which lead us to categorize it differently. It’s a very intriguing idea though, I’d love to see it carried out with a separate long acting basal

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@Sam, are you talking about looking at how changing the amount of long acting basal in a day impacts your meal shot needs?

If so, we have a lot of information on that. Women experiencing fluctuating basal needs, whether on shots or on pumps, navigate this complicated relationship every few weeks. On Lantus, I managed fluctuating basal doses and sensitivity every week…i.e. I’d need a step up each week for four weeks. But there was a tipping point at which to make each change. In other words, my basal would be not quite enough, then really not enough, and then I’d up my basal dose, and then it’d be a little too much, then just right, then not quite enough, then really not enough, then I’d up it again. Each day I’d adjust my meal shots and correction shots according to how well my Lantus dose for the day was matched to my sensitivity.

I experience the same thing on the pump.

We have a lot of information about this concept in some of our basal rates threads elsewhere on FUD. I’m glad to see the attention it is getting on this thread though.

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