Basal requirements on hybrid closed loop pump

[Flower]

What happened to the amount of basal insulin you needed when changing to use a hcl pump?

I'm starting in 2 weeks and wondering what might happen to basal requirements once I know what I'm doing with the pump/Dexcom and can start to loop. I know everyone is different and diabetes is totally individual but did your basal stay about the same, decrease or increase?

I'm feeling quite nervous about changing to something new especially living without hypo awareness but also interested to see what happens. Thanks 🙂

 

[Sally71]

Now that is an interesting question, and one we haven’t thought much about! We kept the underlying pattern the same, on which the pump bases its calculations, but when you look at the pump download now the graph of basal used now looks like the New York Skyline rather than a series of flat plateaus. How much more or less that it actually uses per day I really don’t know! One thing we did notice, was driving daughter into college one day and she got an alarm saying only 4 units left. No problem, we thought, she’s only going in for an hour, won’t be eating anything, and the highest the basal every goes is 2 units per hour in the evening. So 4 units will last easily. Unfortunately, during that hour the pump detected a GB rise and whopped in a correction dose, so by the time we were driving home again we were getting empty cartridge alarm. Be aware of this!

 

[SB2015]

Hi @Flower I am not sure what happened to my basal patterns when I switched to looping. On my system this is adjusted every five minutes without my intervention. The pump requires at least three days in manual before it starts, as it uses that data for its initial decisions and then adjusts from there to match my needs. I think that yours will be based on the basal profiles that you already use, so is likely to do A better job than that as it will be making regular adjustments to that to suit your needs.

I found it very difficult at the beginning to just let her get on with the job, but once I did that she does a good job most of the time. I respond to her warnings, otherwise she gets in a strip, which is fair enough as she has taken on most of the work. I have tweaked my warning limits to suit me, and it works.

I look forward to hearing how you get on.

 

[Finn]

I switched from MDI to HCL (Tandem T:Slim with Control IQ and Dexcom G6) in March. From your signature, it looks like you're switching from a non-looping pump to a looping one, so the below might not be relevant to your situation.

On MDI, my basal (Abasaglar) was 8u per day.

On HCL (Novorapid) my 30 day basal average is 4.8u per day.

The basal profile my clinic set up for me initially (based on my 8u Abasaglar per day) came to 5.1u per day. That was pretty close to what I needed, but basal testing showed I needed a tiny bit little less than that.

My bolus ratios all changed too when I went on the pump and overall I need less insulin now compared to MDI.

 

[everydayupsanddowns]

Just looked up my 30 day average, and basal is currently running at around 36% TDD, with 60% food and the rest in corrections.

I’ve run approx 40:60 basal to bolus for as long as I can remember, so it’s not all that different?

Basal suspends to remove some of the total basal per day I suppose?

 

[Finn]

Just looked up my 30 day average, and basal is currently running at around 36% TDD, with 60% food and the rest in corrections.

I’ve run approx 40:60 basal to bolus for as long as I can remember, so it’s not all that different?

My 30 day average is 20% basal, 77% food, 2% corrections.

That puts me at around 20:80 basal to bolus on HCL.

On MDI I was closer to 30:70, but I wasn't doing as many corrections as I do on my pump now. I'm very sensitive to insulin, so even the minimum of a half unit from a pen would make a big difference. Being able to do as little as .05 units on a pump is very useful for me.

 

[Thebearcametoo]

Our team suggests a 40:60 ratio of basal to bolus or thereabouts but everyone’s needs are different. What they do look for when looping is they like to see the basal cut out especially overnight some of the time which we then have to watch out for if he’s not wearing a sensor for a few days as tends to wake up hypo otherwise. If you’re already pumping then leave things as they are for now but see what happens with the algorithm. There will be some tweaks needed anyway but gather data for a couple of weeks before jumping in.

 

[everydayupsanddowns]

That puts me at around 20:80 basal to bolus on HCL.

How are you finding that split @Finn ? Are you getting results that you are happy with?

Some clinicians suggest that an average non-D produces approx 50% of their own insulin for background stuff, and 50% for meals.

John (Pumping Insulin) Walsh says most with T1 will be between 60:40 - 40:60.

I get a little twitchy when my split gets much away from 70:30 and wonder if my profile/settings need a bit of a tweak.

 

[Flower]

Thank you everyone 🙂

I’m hoping my basal will stay much the same so I can feel as confident as possible with changing over. My 30 day split is currently 62% basal 38% bolus and that is working well for me at present.

I’ll be interested to see what happens, I’m probably over thinking things!

 

[Finn]

My 30 day average is 20% basal, 77% food, 2% corrections.

That puts me at around 20:80 basal to bolus on HCL.

How are you finding that split @Finn ? Are you getting results that you are happy with?

This works quite well for me.

My final Hba1c before switching to a pump was 5.6% (38 mmol/mol). A month and a half before that it was 5.9% (41 mmol/mol). So the 70/30 split worked for me on MDI.

I had one Hba1c about a month and a half after switching to a pump, which came back as 6.3% (45 mmol/mol). That was taken just days after recovering Covid (my TDD almost doubled at the peak of my illness and blood sugar ran much higher than usual for a week), so I don't think that increase in Hba1c is representative of the control I have on the pump.

The 20/80 split works well for me. I spend most of my time in range and don't have many lows below 3.3, or highs above 13.

 

[helli]

@Finn out of curiosity, what is your diet like (is it very carby) and do you exercise much?
I ask because I think my ratio is about 35:65 on a "normal" day but basal goes down about 25% when I exercise and sometimes it can give me more carby cravings which I am happy to give in to because my TIR is fine and my BMI is healthy. On these days, I suspect my ratio is closer to 25:75

 

[Finn]

@Finn out of curiosity, what is your diet like (is it very carby) and do you exercise much?
I ask because I think my ratio is about 35:65 on a "normal" day but basal goes down about 25% when I exercise and sometimes it can give me more carby cravings which I am happy to give in to because my TIR is fine and my BMI is healthy. On these days, I suspect my ratio is closer to 25:75

I'm vegetarian and I eat about 100-120g of carbs a day, but I don't restrict it. I count the carbs for dosing, not for limiting my carb intake.

About 2/3 of my plate at every meal (breakfast, lunch and dinner) is raw veg - cucumber, peppers, cherry tomatoes and carrots at every meal, no dressing - except on the rare occasion when we eat out. I don't bolus for protein and I don't count the veg in my carb count, although it probably adds quite a few carbs to every meal.

A few times a week I get a pastry or sweet from the bakery and cut it into several portions, coming to about 15-20g carbs each, and enjoy it over a few days as dessert or to preemptively treat an oncoming low.

My exercise consists of 3-4 hours of walking/hiking a week and each walk is about an hour. Walks are usually after breakfast or lunch and I bolus 1/2 to 2/3 my usual dose for the meal before a walk.

I work from home, so no movement from a commute to plan for, and most of my day is spent at the computer. It makes it easy to control (at least a little) other factors to have a bit more predictability with my blood sugars.

One thing that may affect my basal to bolus ratio is the fact that I was just diagnosed in August 2021, almost two years ago, so I might still be in the honeymoon period.

 

[everydayupsanddowns]

The 20/80 split works well for me. I spend most of my time in range and don't have many lows below 3.3, or highs above 13.

Great to hear!

 

[Inka]

I never get the basal/bolus split thing because it depends on how many carbs you eat, and also percentages are affected by how large/small your basal and bolus amounts are. Maybe I’m missing something (probably! ) but, say, at Christmas or similar when I eat lots of carbs, my basal/bolus split will be very different from when I’m somewhere hot and eating far less carbs. I’ve never bothered to work out my splits or pay them any attention. Tell me I’m not missing something

 

[Finn]

I’ve never bothered to work out my splits or pay them any attention. Tell me I’m not missing something

There's nothing to 'work out' for pump users, at least Tandem T:Slim users - it's all calculated by the pump. I'm not sure where it is on other pumps, but on the T:Slim it's Options -> History -> Pump History -> Delivery Summary.

I do don't anything with my splits except look at them once in a while to see if my basal to bolus ratios are more or less consistent in the 7-day, 14-day and 30-day averages. I don't aim for a certain ratio or feel the need to try and change it, I just like to see what it is out of curiosity.

 

[Inka]

But corrections and pen boluses? Why would you be concerned with consistency? I genuinely don’t get why anyone would care about the split.

 

[Finn]

But corrections and pen boluses? Why would you be concerned with consistency? I genuinely don’t get why anyone would care about the split.

I'm not concerned with consistency in the split, I just notice that it is consistent. If the split veers off too far from my usual, it could be a sign I need to do some basal testing. But only because my split tends to be consistent, not because I feel it needs to be a certain split.

I look at that Delivery Summary screen mainly to see what my average TDD is. Whenever it starts to creep up, I can be on the lookout for my honeymoon period is coming to an end and re-evaluate my basal and bolus approach. Right now, it seems pretty steady at 20-25u per day basal, bolus and corrections combined.

I have no idea why people are told certain splits. It could be just a good general starting point for figuring out basal rates and bolus ratios after diagnosis. But you need what you need. You just need to figure out what that is.

 

[Inka]

Out of interest, I’ve just checked my pump (DANA i) and it doesn’t seem to have the basal/bolus split in the History. There are lots of other things there but not that. I just looked through the manual too and couldn’t find it.

Perhaps people who eat a very regimented diet (same meals, same carbs, etc) would find it useful, but I just eat normally and calculate my bolus based on the carbs. Some days I eat lots of carbs, other days an average amount, some days not many. I’ve just picked two days and calculated the split manually. It was 32/68 (basal to bolus) one day and 58/42 another. The difference in those two splits was the amount of carbs I ate on each day.

It’s similar with TDD too. My TDD would have been different on those two days above, with the day with more carbs having a higher TDD. I don’t count my TDD either. If I was worried about insulin resistance, I’d become aware of that as I adjusted my basal and my meal ratios. That, to me, would be a better indicator. Needing more bolus would just mean I’d had more carbs and so the TDD would naturally be higher. When I was pregnant, my breakfast bolus almost quadrupled due to the IR of late pregnancy. It was my bolus ratio change that I looked at, not my TDD, if that makes sense? My basal also increased too.

You’ve said the most important thing: you need what you need 🙂 So many things can affect our insulin needs: carbs, resistance, exercise, heat, stress, hormones, etc etc, etc. It seems pointless to me to waste time thinking about too many figures too much.

The end of the honeymoon can be quite sudden, but usually it happens gradually and you become aware of it by realising that day to day changes aren’t one-offs, they’re more permanent and show a drift. My honeymoon lasted a long time. There were various steps down in my insulin production with the final ‘step’ being some years after diagnosis, so a gradual decline. I’m sure you’ll spot it 🙂 You get a feeling that things are changing. Hard to describe but you’ll know it when you see it.

 

[Finn]

I guess my bolus average is consistent, but each day varies. I'm pretty sensitive to insulin and a little goes a long ways, so my TDD is usually within a few units of my average unless it's a one-off, like a birthday or holiday.

Today was movie day and I went all out on snacks (we watched the 3 hour long new Avatar and took a few breaks). I had a brownie with strawberries, more strawberries, popcorn and some chocolate. My TDD is on track to hit 28u today, but that balances with a 19u day I had recently when we went on a long walk, so it all averages out and I still feel like I'm eating 'normally'. I guess I'm consistent in my averages (7-day, 14-day and 30-day), but I can be pretty varied day to day (28u TDD today, 19u a few days ago).

With the end of the honeymoon period, I think the pump data will help confirm my perception that it's ending, whenever that happens. With Covid, being able to see I was averaging 40u per day instead of my usual 20-25u made it clear to me just how much of a (temporary) change Covid forced me to make.

I like looking at the data, but I don't change anything based on my basal:bolus split. If my average TDD increased and lined up with weight gain, then I might do something. ;-)