Tandem T-Slim

What is the lowest basel rate I can set on my Tandem pump. I have the G6 Dexcom Sensor. I discovered that my basel rates have been set too high and that is why I am having lots of low BG events. I need to set my basel to 0.05 and am unable to do so. I use the Carb feature.

I may be able to accomplish the same thing by changing some of the personal profiles.

I have a new Endo and the NP changed my IC from 1:20 to 1:29. For awhile right after the change I was running too high so I changed it back to 1;20 and started running low. i began adjusting my basel downward and am still running low a lot. Not sure what I am doing wrong.

Any help is appreciated.

0.1 u/he is the lowest basal rate Tandem can be programmed to, but it can deliver smaller amounts. If you really require that level of insulin sensitivity, it is generally done with diluted insulins, as no pump is capable of such accuracy given the margin of error that goes with the mechanics. (Technically, Medtronic is capable of being programmed that low, but independent tests have shown they’re incapable of accurately delivering such. That syringe-style pumping mechanism is “leaky”.)

It can also be done via programming alternating segments of 0.1 and 0 u/he, but that’s not nearly as safe as diluted insulin, because you’re essentially forcing the pump to operate outside it’s specifications.

That said, I would call the NP back and give them another chance to help you correct the problem. Are you using Control-IQ? Because I find with Control-IQ getting your correction factor(s) set right is paramount to any other setting on the pump, because it’s the main thing basal adjustments are made from. Thus is especially true if you’re one of the “sleeping beauties” running sleep mode all the time, where it’s making constant basal adjustments. A single number change can make a massive difference. I would never change mine more than 10% at a time (and I’m nowhere near as sensitive as you), and both you and your NP are making MASSIVE adjustments. If changing the correction factor that much solved the low problem a little too well, maybe your sweet spot is actually somewhere in the middle.

And as always when I come across someone who is especially sensitive to insulin like this, I HIGHLY encourage you to do some research on MODY, a type of diabetes that is nearly always misdiagnosed. It’s typically characterized by later-life (not as a young child) diagnosis and extreme sensitivity to insulin (your basal rate is less than many infants/toddlers). Does that sound like you?

That fact is, there’s still a lot of ignorance about diabetes, even amongst the professionals. They’re just not trained to look for special cases, but rather lump everyone into broad “one size fits all” categories. There are actually 11 different genes which contribute to diabetes. With MODY, only one single gene got screwed up. Meaning that there’s one single protein that MODY patients can’t create. It’s different than Type 1, where our immune systems destroy the physical production center and we just can’t make insulin and other hormones. It’s more like a coding problem, while the physical structure remains intact. MODY patients are just missing a single link in the natural chain.

The treatment for MODY varies, depending on which gene it was that got damaged. In many cases, insulin is indeed the right treatment. But in some cases, there are actually oral meds which can replace whichever protein you’re not making. Don’t confuse them with the many Type 2 oral meds, which many adult-onset patients have tried and didn’t work. These are different. You can’t just say “I tried oral meds and they didn’t work for me”, when you’ve never tried the RIGHT oral med."

The potential for oral meds is precisely what makes me so excited about MODY. Unfortunately, I’m a very traditional childhood onset, so it will never apply to me… but I’m fascinated with this idea of a magical pill being able to take the insulin nightmare away. Yet, I’ve learned that potential-MODY diabetics I’ve encountered get attached to their current diagnosis and are hesitant to pursue this route. I’m guessing because many late-onset patients have already endured the Type 2 misdiagnosis process, just because they were adults when they became symptomatic… And this idea of finally getting a Type 1/LADA diagnosis was such a great relief that it’s hard to let go of. It’s a simple generic test to determine MODY, and yet almost none of these super-sensitive to insulin people that I’ve encountered have actually had the test done. I would be all over any potential for a magic pill, myself!


Thank you for your careful response. I only wish I had been been misdiagnosed. I have been living with this since the age of 17, I am now 75. I am what they used to call “Brittle Diabetic.” It seems that no matter how closely we set my parameters, my diabetes has a mind if it’s own. Today’s low insulin need, will change in a few days.

Yes; I am going back to my NP for re-evaluation. Of course, if life were perfect; I would always be correct in my carb counting, I would bolus 30-minutes before eating a meal, and all the other things we need to do.

For instance, it is 4:08 pm and my BG is 105 and dropping. Even though I am eating 2 Glucose Tablets, it will continue to drop into the 50’s before it stabilizes. If I were to eat 3 or 4 it would immediately go to 250 or higher and down the rabbit hole we go. I am trying to simply avoid the lows.

I am perfectly capable and willing to learn how to resolve this problem. However the CDE’s do not have time to work through such things. I a a new patient and cannot see one if their CDE’s until September and for one hour. They just do not have time to help someone with complicated issues.

I will keep trying to figure this out. Thank you for your input.

I would suggest carb gel instead of glucose tablets.
There are several on the market. GU and Hammer and Cliff.
They will correct a low without a big rebound like glucose tabs can do.

Some suggest they don’t raise you fast enough, but I find they work fast and also stick around longer.

Thank you, I will buy some.

Sorry for all the MODY talk, then. I just get overly excited about it whenever I see someone inquire about the lowest possible settings, when they presumably weigh more than 10-20 lbs. It’s that fascination over the magic pill.

What you say makes perfect sense, though. I get annoyed myself for the ever changing settings, but I always assumed it was my variable inflammation that did it.

I think we should ask be confident in tweaking our own settings, so long as you do it in small increments. Especially with a CGM, since it removes a lot of the danger factor. Honestly, I thought it was irresponsible of the NP to make a nine digit adjustment all in one blow.

If it were me, I would pick a number in the middle and tweak from there. If you’re using Control-IQ, you’re specifically looking for over- or under- corrections that are delivered by the system. If your CF is too low, you’ll feel like you’re on a rollercoaster. It will correct sugars above target with too much insulin, driving you low, and then it will withhold too much insulin when you’re down there causing you to rebound high. If the CF is set to too high of a number, it will cripple the entire system and Control-IQ won’t be able to change the trajectory of your BG. If you’re going high, you’ll keep going high and can’t get back down. If you’re going low, you’ll just keep going low and it won’t be able to intervene in time. Ideally, a spot on CF will look like gently rolling waves around your target BG and you’ll know you finally found your sweet spot.

Hope that’s a little more helpful.

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Absolutely helpful. Thank you. That is my situation exactly. I know my settings have never been accurate. I have never been able to test my setting because I either go too high or too low. But I just keep trying

Thank you.

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You hit the nail on the head. Your last paragraph is my situation exactly, all of it. I am convinced that my CF is way off, which way I do not know. I was doing some online research (we all know that is wise) and it appears from several of the articles that mine should be around 50, a long way from 20.

When my BG starts going high, it just keeps going and I end up chasing it with boluses that then send it low. When it is low; I risk rebounds.

Though I have been on a pump for 40 years; I don’t think I benefit from it like I should. Of course, it is so much better than six shots a day and all that goes with that.

I love the Pumping Insulin books and they do address my problems, but there is not one chapter that defines what each parameter we set is and how to achieve the right number. When I have to jump all over the place to figure it out; I get lost.

I have been told by those who should know that I should be able to eat or not eat, eat whatever I want to, and keep my BG in range. Fortunately, for me; I do not live to eat. I don’t like to eat breakfast, and forget to eat something as soon as i get up. If I don’t eat something, then my BG goes over 200 and the daily struggle begins. If I do not have time for lunch, then I deal with lows. I am always in perpetual motion, not exercise but always busy. Sitting is not my friend and so I stay on the move.

I am going to copy and take your observations to my NP and insist that I see him often until we figure me out.

Thank you again,


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Your settings are very contradictory. I didn’t even notice that until you mentioned it. I was stuck on the unusually low basal. 0.1 u/hr basal suggests that you’re incredibly sensitive to insulin. Basal rates vary a whole heck of a lot, so I’m talking generalities here, but they average around 1+ u/hr (you don’t even have to exclude children, because all those crazy hormones make them need more insulin proportional to their weight than adults). 0.5 u/hr might be possible if you’re really small and/or really active, but you’re getting into unusual territory there. 0.1 and less isn’t “normal” at all, hence my spiel about MODY. It implies you still have some capability of producing insulin yourself, or that you’re getting metabolic assistance somehow. On the other hand, your correction factor suggests the exact opposite, that you’re insulin-resistant. 1:20 is something you’re more likely to see amongst Type 2 populations, who tend to require extra insulin, than Type 1. Maybe that’s why your NP made such a big adjustment?

I have a sneaking suspicion that you’re treating yourself largely based off of your correction factor alone. As in, your basal is doing nothing, and you and/or the pump automation are over-correcting to compensate. That would make perfect sense of the scenario you described. Since we become insulin-resistant when we’re high, you can’t really judge your settings based on how hard/fast you come down from elevated sugars. Those are always difficult to bring down. The being stuck up high doesn’t mean you need a lower correction factor, it means you need to stop the high in the first place with better settings. Earlier, when I described that a too high CF would look like you were stuck in your current trajectory… Can you see how not getting the basal insulin you need would also cause a similar rise, masking the problem? You might think you need to lower your CF, because you can’t get down and need a more aggressive setting, but in actuality the rest of the pattern suggests the CF needs to be increased AND the basal too

I know you say you can’t really do basal testing, but you need to not make excuses for it and just suck it up and do it. Not trying to be mean at all. Consider it tough love. But when you approach something this critical with that “I can’t…” mentality, that’s precisely what you’re doing, and you’re just defeating yourself. It’s honestly the only way you can figure this out, because you’re settings are so far off. Thus will be like starting from scratch. Control-IQ can handle the day to day variations, but you’ve got to give it a baseline to start from. When you’re not fighting your own settings all the time, you might just discover that you’re not nearly as “brittle” as you think you are.

I really hope you get this figured out! We all understand the frustration of bad settings, but there’s this HALLELUJAH moment when things click and life with diabetes suddenly gets easier. It’s worth the extra work now, I promise.


@Nan, I would encourage you to take @Robyn_H’s suggestions to heart. There are very few doctors who are expert in making pump setting changes and who also have enough time to follow up with pump patients like you on a daily basis until a working solution is found.

I’ve worn a pump for 35 years now. It wasn’t until I took full ownership of my glucose management (9 years ago) did I learn enough to manage my pump myself. I was someone who tried to manage his best but was missing some of the fundamental knowledge that pumps require. I therefore trusted my doctor to make various setting adjustments four times per year.

I soon realized that my doctors didn’t know nearly as much about managing pump settings as I thought they did. In fact, I remember realizing that I was the only one with sufficient motivation and time to become the expert that I needed. Clinicians simply do not have the time to actively manage pump settings for a few hundred different patients.

Pump settings are a target that moves. If you don’t move when your body’s requirements change, you will get left behind. Diabetes is dynamic, not static. When diabetes changes, you must follow or your glucose health will degrade. This is a case where the pump wearer is the only logical person to assume the role of diabetes owner and then make competent and rational changes as and when needed.

Your situation perfectly typifies the biblical notion that it’s much more important to teach a woman how to fish rather than to directly feed her fish! If you choose to rely on your doctor to step into this role, it may never happen and you may realize too late that the doctor is not as competent at pump management as you had thought!

I know you are a few years older than me, Nan, and I understand we can be frightened with what our advancing years mean to our ability to manage glucose levels. Our brains, however, are like muscles; if you work it, it will get stronger. If you challenge it less and less it will become less capable.

If you don’t think that you can take this task on alone, perhaps you could find a competent coach (or diabetes educator) who could work with you as much as you need to learn how to manage your diabetes better. Communicating through an app as part of a continuous remote support system is what you likely need.

Just realize that you need this person to demonstrate the ability to successfully work with people like yourself and to be available as often as you need it – as often as every day. Diabetes doesn’t take a day off and neither does the requirement to manage it!

Unfortunately, identifying someone with that competent skillset is not easy. There are plenty of people who like to think they know about managing insulin treatments well, but they don’t. It helps if this person lives with diabetes themselves and uses a pump.

You might look into hiring Integrated Diabetes Services to help you through this. The founder of IDS, Gary Scheiner, has T1D himself and has written several books about managing diabetes. Also working at IDS is Jennifer Smith, a dietitian who also lives with T1D.

Sorry if I’ve just raised more questions than I answer! In summary, I think you should commit to learning more about identifying and setting basal rates as well as identifying and setting appropriate correction doses. See if your doctor can recommend someone to work with you. You can do this!

These new skills, however, are not something that comes automatically or quickly. You do have to do the work. But then you will find satisfaction and confidence in these newly improved skills and quality of life.


I hear you, but can also assure you that my not being able to do the testing is not a “a suck it up problem.” I am not offended. Everytime I try to do the testing; I can’t get beyond the first step because my BG drops, I have to treat, and start over again.

Trying to help someone with only partial facts is frustrating and hard. The 0.1 I mentioned is new. My Basel is usually 0.3 to 0.6. In my effort to stop the crazy lows; I decided to see if lowering the Basel would help. Just grasping at straws here. I had already printed out the instructions for testing again. I am going to put together a short term menu that will possibly help. So no 0.1 makes no sense just something I tried.

So you are dealing with a full deck of information, my setting are as follows.

Basal 0.3 to 0.6. Correction 1:29. Carb Ratio 1:11
Target 110

Sound more like it, right. Sorry for the confusion. Your description, as I stated, is right on. But I do not know where I am going wrong. I am super sensitive to carbs and a slice of bread sends my BG through the roof in a short period of time.

Just so you know; I have been hospitalized where they monitored my food intake, Boluses, settings, and exercise. We did the same exact thing, at the same exact time each day, and the results were erratic. I have been tested numerous times to see if I produced any insulin; I do not. Yet my Endo has always questioned whether I might get a periodic shot of insulin from my pancreas. No way to prove that. For the first time I am now battling a weight gain. Trying to take it off and do not likevitvine bit.

Now you have a better picture.

Thank you. I guess my posts fail to communicate how diligently I work to meet the goals of balanced diabetes care. I have always taken ownership of my disease. As you say; our pump settings are a moving target. Diabetes is a moving target. I developed diabetes, literally, in the dark ages of the disease. I was actually told that I would probably not live past 42. That was sobering to a newly married 17 year old. Yet, here I am, 75 years young, still married, and not because I depended on the doctors. Neither do I have any of the complications that most long term diabetics have. The pump has been a God Send for me. I am not lazy, certainly not mentally. I constantly read, research and study.

My question about the lowest possible Basel rate is the result of a recent effort to control low BG’s that are currently plaguing me. I am not good with numbers, and I do not claim to have a full understanding of how the CF, Basal, and
Carb Ratio work. The only one I have ever been instructed to change is the CF. I do change the Basal, not often but when I start having too many highs or lows.

I have searched high and low for an independent CDE to educate me so that I know how and when to make adjustments. In my world at least, they do not exist. I know I am perfectly capable of understanding these things, but the maze of information available, is frankly clear as mud.

You can be assured I will use the information Robyn has given me to make adjustments. I always learn from others, value their opinions, and test their theories. Most of the time I do really well, have good A1C’s, but when things go awry I try to figure out why, what changed and adjust accordingly.

Since June 3, I have been struggling with Pneumonia. My lungs are still not clear. We know what any infection does to diabetes management.

Thank you for your input and encouragement. I will never get it perfect but will keep trying. Diabetes is not an exact science but we have to deal with it or it will deal with us.


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I’m sorry if my words did not acknowledge your efforts. As a peer, it can be hard to decipher the full situation while trying to help shed some light on your challenge on aspects you may not see as well.

It’s a delicate balance between offering sincere recognition to the person seeking help while also reflecting back some items that may not be flattering. Plus, I fully realize that from my distant perspective through the lens of the remote written word, it can be presumptuous to think I can see the full truth.

Your diagnosis at 17, followed by 58 years of the grinding demands that diabetes issues, does put some things in perspective. You have done well treating your diabetes. I was diagnosed in 1984, 21 years after you, and I know that the treatment choices were few and the tools crude. I started out on one per day of NPH and then added Regular meal-time insulin, a system responsible for some harrowing hypos.

Yet, I think, with the addition of some more training, your glucose results can improve by a lot. And those improvements will immensely add to the quality of your life. The help of a coach or diabetes educator could make all the difference to you at this point.

It would be great if seeing a doctor four times per year were all that would be required to pacify your blood glucose but that is wishful thinking. In my humble opinion, sustained help and training is what you need. You could accomplish this on your own but I think that getting some personalized help would be your shorter path to success.

I didn’t intend to demoralize you. I was more interested in being a provocative healthy irritant and I guess the irritation was a bit more prominent than needed. You are doing well and I think you can do much better!

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I apologize if I sounded offended. That was not my intent and I fully understand that trying to decipher all the unknown facts is like asking someone to read your mind. Appreciated what you had to say then and today. We lived in a city with great medical care and then moved to a small town in Louisiana. Medical care here is adequate but not the type I was accustomed to. I fully intend to look into the resource you suggested.

With Robyn’s encouragement I was able to determine how to reset my parameters as a starting base. It appears to me that my CF has been way to low, causing the lows. It has been awhile since I did a major change in my settings. However; I began having lots of highs and way to many lows. I am still pretty sensitive to insulin and have to be careful. I am super sensitive to carbs and just a small amount sends my BG through the roof. I don’t eat potatoes, bread or pasta often and then in small quantities. I don’t eat fried foods, yet still deal with ups and downs, and for the first time weight gain.

Yeah, I am a mess right now and a coach would be a blessing. I have tried using a dietitian but they are not diabetics or trained as such. I will find the help I need. With TeleHelp prevalent now; it should be easier.

Thank you again for your concern.


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Interesting as my basal rate for some time periods is 0.075 IU/hr with Medtronic 670G. And that’s without temporary basal. Are the tests published anywhere accessible on the web?

Definitely. I’ll provide some links, but I highly encourage you to do your own research on it if you’re curious. I tend to hate providing links because they’re a narrow glimpse of a topic, and I think the most insight comes from digesting the info from different sources. A quick search on PubMed alone revealed 119 articles regarding “insulin pump accuracy”.

The most commonly referenced study is this 2010 one, though:

Where they concluded,
Changing position of a conventional CSII pump in relation to its tubing results in significant changes in insulin delivery. The siphon effect in the tubing may affect the accuracy of insulin delivery, especially during low basal rates.

Note, I’m not necessarily picking on Medtronic. This is true of all “traditional” tubed pumps where the reserve of insulin is directly in line with the tubing/infusion site… Medtronic is just the only one left in business in the US still using this pump mechanism. And even though this particular study is dated, it’s still relevant precisely because the pumping mechanism hasn’t changed.

I do think you can successfully pump with these systems, I just don’t think you can actually know the volume you’re getting. I think of it as one of those “the devil you know” situations. In the end, it doesn’t matter if you’re getting 0.75 or 1.25 u/hr, so long as your settings are adjusted to your particular pump’s quirks and your particular needs. I do think it’s important to understand this flaw, though, so you appreciate the need for consistency in how you wear your pump. Over- and under-delivery of these pumps is a common theme in the MAUDE database, where “adverse events” (I e. hospitalizations/deaths) are reported, and could have possibly been avoided if there was more talk about this problem.

It’s actually the entire premise Tandem’s original T:slim was built on. Unprecedented safety with their Micro-Delivery platform, which moves insulin to be pumped into an intermediary and isolated chamber, so the reservoir of insulin can’t leak into you.

I also think this article is interesting, as it talks about the difficulty in measuring pump accuracy in the first place, and illustrates how the method dictated by the FDA to do so is ineffective for measuring especially small flow rates. So maybe none of us know what we’re pumping.

@Robyn_H – I was marginally aware of this phenomenon as these studies were published several years ago. This effect of getting more or less insulin based on the vertical distance from the infusion site was hidden from me since I’ve almost always used abdominal infusion sites with a pump clipped to my belt. When sleeping, the pump is likewise only a few inches below the infusion site.

I use a MiniMed 722 pump with 43" tubing. I’ve never used my arms or legs as infusion sites except for my brief foray using an Omnipod several years. This imprecise delivery influenced by vertical height differences and the siphon effect would argue against using a tubed pump attached to a belt feeding an infusion site in the upper or lower body.

It’s good to know about this effect but it has made no difference to me. Infusion set occlusions, cannula tip tissue immune inflammation, and impaired tissue absorption have episodically hampered my glucose control at times. These factors alone were complicated enough to manage and I’m glad this siphon effect did not further compromise steady insulin delivery for me.