Tandem's basal

Forget it! I couldn’t explain it.

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Lets get rid of the decimal place completely.

Your not delivering 1 unit, your delivering 1 unit per hour.
This number represents a rate of dosage administration, not how many units are being delivered.

If your pay rate is $1 per hour, and you only work for 15 minutes (1/4 of an hour), how much do you get paid?

If your pay rate is $1 per hour, and you only work for 45 minutes (3/4 of an hour), how much do you get paid?

I think it’s just really unusual for anyone to require less than 0.1 units of insulin per hour as a basal rate. My son was diagnosed when he was 3, and he never needed rates that small. Most people who do need rates less than 0.1 can be accommodated by alternating between zero basal and 0.1. Tandem’s increments can be set in 0.001 after that, so very small adjustments can be made. As others have mentioned, you have abnormally low basal needs for an adult T1.

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Maybe this is the way to think about it…This is how the math works if you are making $1 per hour, ten cents per hour, or one cent per hour. If you work for 15 min, you make the following amount of money.

The numbers dont change. Its just the decimal place that is messing her up.

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That’s not how I understood her comment. I understood it to be complaining about the fact that the lowest basal rate that can be set on the t:slim is 0.1.

Yes, and the nurse was able to achieve a basal rate of 0.025 by only delivering that 0.1 units per hour, for 15 min. But, it makes everything look really messy and confusing on paper. It would be a lot less confusing if they were delivering a rate of 1 unit per hour. Its the decimal places that are confusing her.

So, if you want to turn $1 into $0.10 (ten cents), you move the decimal place one place to the left. If you want to turn $1.00 into 1 cent, you move the decimal place two places to the left. You do the exact same thing with the rate of delivery.

I’m not able to explain this in a simple way. This stuff will make her uncomfortable forever.

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Okay. I guess I’m used to seeing this, as before my diagnosis I spent a lot of time on Children With Diabetes forums. There is lots of monkeying around there with alternating basal rates in order to accommodate babies and very small kids. Maybe that’s why I didn’t understand the confusion. Regardless, it seems to stress the OP out a lot, so I agree that she’s better off with a different pump, for sure.

Look at her basal profile here, @hawkeyegirl. Its super confusing.

This is only half of it…

I got it.

You mean .100 (per hour) minimum entry per segment.
So if segment is 15 minutes, .025 is delivered in 15 min.
Then next segment is 45 minutes for .000.

After 1 hour, net .025 units/hour has been delivered for that hour.

But it would be “front loaded”, and as experienced, led to lows. Tslim can suspend basal, but not effective when last 45 minutes of segment basal is 0.

The ideal setting is supported by medtonic pump, which allows direct basal segment to be .025 units per hour, spread over entire hour, not just first 15 minutes.

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I’m sorry, but you’re being confusing. You keep posting the same thread, getting the same answers, and then proceed to ignore them. Are you not getting the answers you want? Are you just extremely frustrated and voicing your concerns in a repetitive manner?

The t:slim X2 is most definitely not the pump for you. But it’s by your own choice. You’re unwilling to make the necessary changes. You want it to be just like your old pump, and it’s not.

No, very few people are going to have this problem or be able to relate. Everyone has used very gentle language with you thus far to be polite, but maybe you need something more direct. Basal rates that low are pretty much reserved for infants and MODY, neither of which the T:slim is indicated for, so is not designed for. But neither are the others. Because mechanical devices have a margin of error, it’s not considered safe to use them to deliver miniscule amounts of insulin, when the error might be as big as the dose. Those who want to use those devices off-label, have to use diluted insulin. It is the only responsible way to mitigate the risk. Yet, you don’t want to go that route.

Yes, you argue the MODY thing, but your arguments are invalid. You do not present as a Type 1. Just because your medical team don’t understand MODY, maybe never even heard of it, doesn’t make your diagnosis true. Just because you require treatment or else you go into DKA, doesn’t make it true. (Diabetes is still diabetes, no matter the flavor) Just because an incorrect oral medicine didn’t help you, most definitely doesn’t make it true.

Even given the MINUTE chance you’re not MODY, your insulin requirements are the same as one. Miniscule. Your diabetic team should be treating you as they would an infant or a MODY patient… WITH DILUTED INSULIN.

Diluted insulin is the only safe way to deliver such tiny amounts of insulin, and quite frankly, I think your medical team had been negligent to let you operate in dosages as low as yours, because syringes, pens, and even pumps, just aren’t that precise. What is your backup plan in the event of pump failure? Even if you deliver a half unit bolus on a pen, they have margin of errors too, and that error is significant enough to you too be life or death…

Technically, no pump on the market is an appropriate choice for you since none of them have been approved for infants, who use a similar dose as you. At least not until you switch to diluted insulin.

Tandem was kind enough to list the specifics of the X2 performance at low basal rates.

Tandem T:slim X2:

That chart means that they performed 600 tests where they delivered a 0.1u/hr basal rate and measured the actual volume delivered after 1, 6, and 12 hours. After 1 hour, they measured between 0.09 and 0.16 units actually delivered, and averaged 0.12 units. The mere difference alone, 0.07 units, is greater than your lowest insulin setting. Even the average dose varies by 0.02u from what was requested. That’s 40% of your lowest setting, a significant amount. Your medical team should have known that since you have such exceptional insulin needs.

Unfortunately, I wasn’t able to find a similar test done by Medtronic. Either they haven’t performed the test, or they haven’t bothered to share the data. It wasn’t among the technical specifications in the user manuals I looked at. It may be in the little prescription fine print details insert that should come in the original packaging, I don’t know. So I can’t wager a guess as to how accurately your Medtronic, or later generations, might be delivering your low basal rate, but I can’t imagine it to be better. You’ve already had studies shared with you that illustrate how inaccurate basal profiles can be. Unfortunately, your current pump is just “the devil you know”. You can’t trust a specific dosage to be accurate, but you’ve learned how to dose on your particular pump.

I promise I have no malice towards you in this comment. I’m just trying to get you to understand that your needs are truly exceptional, and your care team is neglecting to treat you as such. You should demand the MODY test, not to shut me up (I’ll happily eat my boot if I’m wrong), but because correct diagnosis is the cornerstone of getting you the right treatment, even if the only difference is the care they take, or maybe a referral to someone more experienced with your special requirements. I’m also scared for you on U100 insulin. You really, really, really should be taking a diluted insulin. The margin of error is frightening… No matter how you choose to deliver it.

I hope you’ll at least take this a little to heart, and not just ignore me because you don’t like me or what I’m saying. I’ll also step aside and not say another word. There’s no advantage for me here, I’m trying to stress these things for YOU.


That basal profile isn’t mine. It is one the tandem rep wrote out for me. I don’t want it.

Its ugly. I fully agree.

The arithmetic is really only the 1st problem in simplifying this basal schedule.
Its a lot to overcome.

I think that looking at the details of it helped me understand basal rates better, though. Its interesting.

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Robin, your answer is spot on. The only thing I would add is that if the basal dose accuracy was available for the Medtronic, it wouldn’t hold a candle to the Tandem. The stiction involved in the Medtronic reservoir piston is too great to achieve consistent accurate delivery. Thus, while the Medtronic may make one feel better about about being able to enter basal values between 0 and 0.1, it is a hoax. The bottom line is it cannot actually deliver that amount in small increments. Alternating between 0 & 0.1 in the Tandem would have a much more consistent end result.


I agree with this fully. Its just MT marketing. You always wanna take what they say with a grain of salt.