Tslim Control IQ and Basal Rate Setting

Hello All, I have a question regarding the basal rate settings in the profile section of the tslim x2 pump. I am hoping someone might be able to help answer. Hopefully I can explain my question well enough to make sense…So the tslim personal profiles allow for different basal rates at different times of day. For example: at 9am the basal rate is .85 but at 12pm it’s .9, and so on for the full 24 hours. The t:connect website allows users to see many different reports and summary information (once you have an account established). Some of the information can also be seen in the pump history on the pump itself. We are using control IQ, by the way…(can’t leave out that important piece of info). I am seeing hourly basal rates much higher than the .85 units that’s in the profile settings. In fact, rarely is the pump delivering only .85 units per hour. I am trying to figure out how control IQ uses the basal setting in the profile. The reason I ask this is because our time in range is very low most of the time. I would like to know if anyone else sees much higher delivered basal rates than what’s in the personal profile settings?

Joanna @WarriorMom13, the t-Slim x2 with CIQ attempts to use the basal rates that are set in the “Active Profile”, but when Body glucose level [the value generated by the Dexcom G6, along with projected change] is out-of-range, the CIQ algorithm either adds more basal or reduces, and then suspends basal delivery to minimize the chance of going too low. Yes, that is a long, and maybe confusing sentence.

When in pump operating mode other than “sleep”, CIG may also deliver a “correction bolus”. Every action the pump makes, those you program such as basal rate change you mention, plus changes made by CIQ are logged in the pump history - and stored there for a long time [90 days?] until the pump memory needs more space to record current activity. Below is an image from the t-Slim User Guide with specific thresholds for automatic delivery changes:

I do suggest that you read the User Guide - I would be happy to help you understand where I feel qualified. The latest Guide is available on the Tandem website - I attached a link below. This is a version that includes material on the software update released a couple of weeks ago. Section 4 has specifics on CIQ.
AW-1007704_A_User Guide, Mobile Bolus, tslim X2, Control-IQ, 7.6, mgdL, Artwork_web.pdf (tandemdiabetes.com)

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Hi Dennis, and thank you for your response. The information you provided is excellent! I knew CIQ worked based off actual and predicted bg rates from the cgm. So would it be safe to assume if the delivered basal rate is always higher than the profile settings, the profile basal rate is set too low? I think the answer would be yes. The insulin delivery rates we are seeing are, in most all cases over 1 unit per hour, with some as much nearing 3 units, and the profile settings range between .8 and .9 units per hour. I think our endocrinologist is being too conservative and want to increase the rate to achieve better time in range. We currently see time in range anywhere between 17 and 40 percent. Very rarely are we above 60%.
Thank you!

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That is a good assumption. It is here that I would like to caution you and say two things:

  1. any changes to basal rates should be small changes. Insulin builds up in your system and so small changes down the line can have big effects later. So don’t go changing every basal rate drastically.
  2. your endocrinologist might have a reason for being conservative right now. Being up front about your frustrations is important. Is your endocrinologist “working with” you or “telling” you what to do? Do you like and trust your endo? If not, it’s time to get a new endo. In my experience, I have tried endocrinologists until I found one that is a good fit for my personality & helps me manage my blood sugars.

Under certain circumstances this could possibly be correct, but other factors most probably are the cause. The first “line of defense” CIQ makes for errors users make is to increase, or decrease, basal flow rate. “Overbasalization” [a term coined by the panel which writes and keeps current the ADA “Standards of Care” for diabetes professionals, has put forth the idea that this might be causing much harm.

I’ve never met your son, and all I know about him is that his diagnosis was made at an age two years younger than my diagnosis, so I’m going out on a limb offering my non-professional suggestions. Before increasing basal rates which already appear high to me, unless your son is quite heavy, is to validate his other Profile settings beginning with meal-time Insulin: Carbohydrate ratios [I:Cr], the Insulin Sensitivity Factor / Correction [ISF], and assure that pretty accurate carbs are entered for all foods eaten - even that “oh, I just grabbed a handful of popcorn”. It took me a while, but I’ve learned I need to be honest with myself, take the insulin and let others know what it means to live with diabetes 24/L. “L” = Lifetime.

I suggest beginning by looking first at his I:Cr for all times he would usually be eating; remember that very few PwD need the I:Cr 24 hours a day, in fact “need” varies greatly and mine are 1:12 to 1:20. Before making a meal time change, look at before meal BGL and see if 4 hours later his BGL reaches this point. If his BGL is NOT as low as the previous meal, he needs more insulin at that time of day - unless his pre-meal BGL was below target. Make changes a little bit at a time, and be aware that he may need to Decrease basal rates for affected timed periods - all insulin infused, either basal or bolus, is incremental and remains effective for about four hours - even though basal does NOT appear in the displayed IOB.

Linda’s @Juggernautical observations a perfect thoughts for you to consider, and I certainly endorse her “… Is your endocrinologist “working with” you or “telling” you what to do?”. T1D is a self-managed lifetime condition that requires action even when a “doctor” is not in your son’s back pocket. A good doctor teaches and provides guidance and suggests changes if necessary - does NOT direct or order.

Thank you all for the responses. I do think our endo works with us rather than telling us what to do. She has “given me permission” to make changes in the past, and said she wanted us to be comfortable enough with “this” to make changes. Our insulin to carb ratio right now is 1:6 at breakfast (to help with “dawn phenomenon”) and 1:8 the remainder of the day…which sounds like alot compared to 1:12 to 1:20. It just seems like we are not getting the results we should using the pump. (A1C was 7.1 last check) I was hoping and expecting to see better times in range (especially with the price of the pump, and it seems like most people have better numbers than we see). I have read the user guide that came with the pump. I just don’t know why it’s not doing a better job of keeping my son’s bg in range. I’ve wondered if some other setting is off, or if it’s basal rates, or if this is just to be expected with a growing “almost” 14 year old. I also have read some (but not all, yet) of the book “Think Like A Pancreas”. It has alot of information…and I have to admit, I have to step away from it some times, in order to keep my own sanity. It also seems like more often than not lately it takes alot longer for the insulin to start working…like an hour or more. This makes me wonder if we need to enter carbs sooner prior to eating. Take this morning for example, my son chose to eat waffles and maple syrup for breakfast at school. He gave insulin maybe ten minutes before he ate because his bg was already rising (he was at 215 when he ate), and I texted him and told him to give insulin. An hour later the G6 was showing 325, and didn’t start dropping till almost two hours after he ate. Two hours after that, he was in the school nurses office drinking juice because it dropped all the way to 52. My theory on this is because he had pretty much an all carb breakfast with no protein, it shot is bg high and the pump corrected in addition to raising basal, and the bolus, which made him drop low.
He had pizza for lunch, and is currently at 223. (Our State does an awesome job with healthy school menus. Ha, ha) But even with healthier options, I’m not sure my child would choose them, so I am not blaming the school really. I don’t know, surely there is something we can do to see better results!

Joanna @WarriorMom13, it is very wise for you to take a step back and care for yourself, just keep aware of your son’s condition and step in when you think it is appropriate. Your son is at an age where he can probably do well on his own as long as feel he isn’t alone. Another thought, don’t try to compare his amount of insulin with anyone else, there are many factors that play a role; at times in my past, I was using almost five times the amount I currently require - and my daily carb count average is more than 230 grams.

I’m not surprised that his BGL spiked 110 mg following that breakfast - mine spiked more than that today after eating a small bowl of oatmeal. Remember that cheese in the pizza will very often cause a delayed BGL spite - I find that a couple of hours after I eat a couple of slices that I need to take a correction dose; it is a factor of the fat content.

How well was your son doing before he began using the t-Slim with CIQ? I’ve often written here that a pump [any pump] IS NOT a magic wand and, is not a plug-n-play device - it takes work. He may find that he can improve his results by toggling CIQ off, creating profile targets that better fit him and learn insulin management a bit at a time. For instance, the meal-time 110 mg/dl with the CIQ corrections may be too strict for his activity level. An endocrinologist with whom I work will not prescribe CIQ for any patient who does not know insulin management - in her words, CIQ is too dangerous.

Is gis t-Slim operating with the new 7.6 software released earlier this month? If not, I suggest that it be installed, it was released to correct a couple of deficiencies, like the possible “over correction” that may have contributed to your son dropping to 52 this morning.

Better days will be coming, and don’t overlook the puberty hormones can be one of the most drastic conditions interfering with diabetes management

Hi Dennis,
Before the pump (which he’s been using for a year this November), his A1C was actually better. I was also very closely tracking his BG every hour, along with carbs and keeping everything written in a journal. He was diagnosed in April, so we moved to the pump fairly quickly. I do feel we didn’t have enough information regarding CIQ, but I had seen how “everyone” had improved time in range and it communicated with the dexcom and thought at the time it would make our lives easier. It has in some ways, but I don’t like sacrificing time in range for simplicity for sure. I did find out on the tandem website yesterday that CIQ uses the weight and total daily insulin as a base line for the algorithm. Neither of those numbers were correct, or update since we received the pump, and of course I have a growing teenage boy so his weight has increased. He’s also using an average of 70 units a day versus the 60 initially entered in the pump settings. I changed both of those settings, and today’s BG numbers have improved some…but that could also be today’s school breakfast was sausage and a biscuit rather than waffles and syrup. I’m hanging in there and will keep trying to figure this stuff out. Thanks for the encouragement. Oh and yes, I believe we have the latest software update…he can bolus from his cell phone. I’ll double check to be sure it’s 7.6.

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You do have the latest software Joanna @WarriorMom13 … As we all know, management is a day at a time and there are many, many aspects that “just occur” that can’t be explained - or controlled. I mentioned yesterday how my breakfast caused a spike - today I had exactly the same measured breakfast, same insulin, and at two hours after eating, my BGL was within seven mg of where I was before breakfast and by 11 AM needed a snack to correct. My explanation? Must have been one of those “sun flares” or some invisible ghost sprinkling sugar on me - yes, that was humor.

i hope the updated weight and insulin volume measurements help.

Ha! Dennis, I’m almost positive we have similar extra terrestrial types flying around our area…only here they are more similar to fairies…sparkling pink tu-tu with sugar sprinkling wand in hand! And that is exactly what makes type one so frustrating! There are so many variables. I could feed my kid the exact same meals every day and still have unexplained spikes and drops!

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