Frustration at inability to lower bg with Tandem TSlim

I am using the Tandem TSlim but it doesn’t really lower my bg when high despite its many mini bolus’s. I finally take over with a “bolus rage” which frequently accomplishes a lowering from 290 to 140. I don’t see any way to adjust it and am wondering why I paid out of pocket for a pump that doesn’t do what it claims. Any ideas? Thanks

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@tahdah793 Hello Patty, and welcome to the JDRF TypeOneNation Forum! I can hear your frustration.

Keep in mind, that unlike a video game, no insulin infusion pump is a “Plug-n-Play” gadget, and contrary to myth, a pump is not magic, no matter what algorithm one might be using. Your t-Slim x2 requires that you begin with “reasonable” Profile settings that fit your body needs, including hourly fluctuations. These settings are basal rates [as many as needed to balance your body each hour], Insulin to Carbohydrate ratios [I:Cr] for times that you may be eating, Correction / Insulin Sensitivity Factor [ISF] for different times of day; and depending on which algorithm you may have active, Insulin Duration and Target BGL.

Yes, it is a lot of work, especially at first, and I don’t want to sound harsh or discourage you. It CAN be done! For instance, I began using the Control IQ the month it became available, and since then my laboratory HbA1c have been in the range of 5.3 to 5.7% - the quarter I hit 5.7% was when I was living through my novel corona viral infection. My TIR - Time-in-Range was really good for the first year plus, but has fallen off for a few months while I’m experimenting with a change in diet.

One thing that MAY help you, is to lower your basal rates and increase your meal bolus. A proper meal bolus, in theory, should bring you back to your pre-meal BGL within 3 to 4 hours - thus not needing adjustment bolus; I still need occasional adjustments. My settings may not work for you, our bodies most likely react differently, on a daily basis, of the total insulin taken, 70 percent [70%] is bolus. I have always been active and my body build is “slim” [BMI about 20] and the daily average carb count of foods I eat is 230 - 250 grams and my insulin balance has been 70/30 for decades - yes, doctors think that is unusual and not wise. My reply to that, as of “one week from today, I will be in the second half of my seventh decade living with diabetes”.

Patty, give yourself time to get your t-Slim adjusted and then enjoy a wonderful ease of management. Do ask questions on this Forum often.


Hi Patty,
I also use a T:slim pump. My first thought is that you might need to change your correction factor. This ratio lets the pump know how much insulin is needed to bring down a high BG.(blood glucose, IE: blood sugar). It is set up in your pump settings as 1:XX. This ratio is how much one unit of insulin will drop your BG. A way to check if your setting is correct is when you have a high BG take one unit. Wait at least 2 hours and check your BG again to see how far it has dropped - - 2 hours is when Humalog/Novolog peaks. Then, check your BG again at 4 or 5 hours after you took the 1 unit of insulin. This is the duration of the insulins mentioned above, meaning, how long the insulin continues working in your body. With this information, you or your doctor can determine what your correction factor should be. It will also let you know what your duration factor is. For some people, insulin works for 5 hours. For me, it is 3 1/2 - 4 hours. Each person is different, so you will have to test to find your correct numbers. There is no other way to do this, unfortunately.
I’d suggest reading the book, “Think Like a Pancreas,” by Gary Shiner. It explains this all much better than I can do here.

Pam K.
T1D 57.11 years and counting!


Hi Patty,
I would suggest changing out the infusion site. From our experience sometimes a bent cannula is the issue. We struggle with highs that are hard to get down sometimes too. We also are not seeing the increase in time in range as advertised. I plan to bring this up at our next endo appointment. It’s hard to know if we are doing something wrong or if it’s the technology not working as promised. Regardless, it does reduce the needle sticks, which is why we invested in the tslim for our 13 year old.

It’s you, not the pump. I hit the same wall. I took time & figured it out, adjustments, tweaks, glucose always handy. Don’t get frustrated. The pump is the best available. I’ve been T1D for over fifty years. My A1C is in the 6.5 range. It’s your challenge. If this old man can do it, so can you.


How long have you been using the pump/CIQ? Doctors stay patients with baseline settings they believe will work - at least as a starting point - but from there is a matter of fine-tuning those settings for the individual. It can be frustrating, especially if you’re thinking the pump is going to function on its own like a working pancreas. Good record keeping is important - taking your carb intake, exercise and health will help you and your doctor determine what needs to be changed, and when. I had one basal rate when I got my first pump, and ended up with a few different ones for different times of day. Can ratios may vary as well. In time you may be comfortable adjusting on your own, but for now work closely with your doctor - providing data - so s/he can adjust your settings.

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I fought the same thing for the first couple of weeks of use of the tandem pump but soon realized that my basal settings needed a fair amount of tweeking but i have seen an a1c of 6.1-6.3 for 6 testings since starting the tandem pump, my 6.3 also during my covid19 period. I am also in the high 80s for time in range and both a significant improvements over my metronic numbers. They are not miracle instant fixes for all of our t1d problems but can help smooth out some of the bumps in the road once you learn how to best use them for your body.

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You didn’t say but I assume you have Control IQ software, and you are speaking ff times when your CGM site and infusion site are both proven good. When they aren’t, basal, boluses, corrections are like target shooting in the dark with an unreliable gun.

What can you do ? You can understand what Control IQ limitations are .

  • CIQ\ can’t correct for extreme mismatches in food boluses or extremely fast, high rises beyond 225 mg/dL. slow them down a little.
  • A rapid rise beyond 180 mg/dl may be so fast that there ls no time to project it or try to dampen it.
  • CIQ won’t try to correct within an hour of a bolus you direct ending . It will only give one correction per hour.
  • CIQ also considers IOB and basal rate.
  • When CIQ auto-boluses, it doesn’t give 40% of the bolus it calculates using the correction factor in your profile time segment. There’s no description of what BG level it uses to calculate the correction.
  • A rapid rise beyond 160 mg/dl may be so fast that there ls no time to project it and increase basal, AND there is a maximum basal rate.

So for an after meal fast, large rise into non-linear correction territory, CIQ is too little, too late, to handle a sharp spike.

But, CIQ can’t prevent you from manually bolusing to correct.

My experience is that if I initiate a correction using the pump’s calculation, it is more effective than waiting for it to autocorrect.
If very high, and IOB isn’t enough to bring the level under 180, I ignore IOB in my override correction.

Other things you can do:
You can eat differently. You can bolus for foods sooner, use extended boluses. and override the pump calculated meal and other boluses.

But -I know my correction factor is correct, and my basal profile, and my ICR for an average meal, and my carb count for each meal is accurate. So the times I’m far above range are now few and far between. Mostly I get plateaus between 180 and 200 mg/dl from things like pizza that last for up top 3 hours. I wait them out and correct when IOB is too low to drop it the rest of the way, or nudge it earlier with 0.5 U when I’m impatient…

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Hi. My son is 9 was newly diagnosed 7 months ago. We started to tandem tslim 5 months ago. We were having the same issues. I told my doctor/ endo the only way i can lower my Sons BG is to stack mini doses or excercise. She said it was Okay as long as they weren’t big doses. I’m not telling anyone on this panel to do this!!!. Its just what my Doc told me was okay for us. I am a stay at home my so I can sit and watch my phone/ dexcom for a low. We also obviously are not able to do this at school or outings. But I’m frustrated bc, in Range is 70- 180, but what some people don’t tell us is anything over 130-140 for prolonged periods damages vessels. So we try to keep in below 130. So why is the tandems target 110 and for sleep and excercise mode keeps you above this. It makes no sense to me. Good luck. We’ve obviously started with the pens at first and were no where near the control we have now. His A1C out of hospital for DKA was a 12.5 then 9.8 on pens, after went from 7 to a 6.2 now with the tslim. Its a lot of work. We might try the smart pen if u get burnt out it keeps track of yout IOB. Good luck!!!

Hi @missynikcjGabe May I ask where you got the information above? I pulled the following from the ADA website, and while 130 is the high number before meals, it takes into account the rise following - with 180 as the desired upper limit.

The American Diabetes Association suggests the following targets for most nonpregnant adults with diabetes. A1C targets differ based on age and health. Also, more or less stringent glycemic goals may be appropriate for each individual.

** A1C: Less than 7%*
A1C may also be reported as eAG: Less than 154 mg/dL
** Before a meal (preprandial plasma glucose): 80–130 mg/dL*
** 1-2 hours after beginning of the meal (postprandial plasma glucose)*: Less than 180 mg/dL*

An A1c less than 7 will average between 154-172 (depending on which charts you use - TBH I checked a few random ones). Certainly the tighter the control, the less risk of complications, and hopefully any that developed would be minimal. However I wonder if your statement may have been taken - or given - or of context? There are guidelines but few things are definitive - higher numbers may cause blood vessel issues, but not necessarily; and even some people who are careful about their control do get complications. In my decidedly non-medical and solely personal opinion, “good genes” or family longevity is a contributor: I had a great aunt who lived to 114, my mom lived to 94, and my dad to 82.

That said, by all means do what is best for your son. Getting him started on health habits early on will take him far. I’m just wondering about the context of your statement. Thank you for contributing!

Melissa @missynikcjGabe, it sounds as if your son has been a good match for the CIQ system, with your adjustments. Keep in mind that the bolus dose produced by any calculator, including the Tandem, is only “recommended” or “estimated” bolus dose. The user is advised to consider [the Tandem pump asks twice for your confirmation] what you know external factors such as completed or planned activity, and body sensitivity. As you probably recall from reading the Tandem CIQ User Manual, chapter 29, is that “automatic correction” is blocked under three conditions, plus when sleep-mode is active. It is during these conditions that I will add manual a correction bolus. Before I enter a manual correction, I review the “pump History” to make certain that I’m not overlapping an automatic correction.

I’m not aware of any valid reasoning for prolonged BGL level above 130-140 mg/dl. For instance, the approved CIQ algorithm while in exercise-mode sets the target range at 160-180. My pump is in exercise-mode for 3 hours most days.

Hello, Dennis their is Plenty of literature and info all over the internet about vessel Damage with prolong blood sugars of 130-140. My Doctor confirmed This. Their is an article out since 2012. David Spero, BSN. A study out of University of Utah, found that vessel damage occurs at lower blood sugars then Docs previously thought.