Tandem T:Slim X2 unnecessary restrictions!

Good Day all, I am posting this to enlighten users of the Tandem X2 insulin pump who may not know it and hope that Tandem sends out an update to change it.
I have just begun using the X2 about three days now and while at work I ran out of novolg insulin. I had insulin in my vial which had about 65 units in it which was more than enough.
After loading the pump cartridge it notified me that I had less than 50 units and the pump requires more than 50 units. WTF! I just finished eating, my glucose is rising pass 300mg and my new pump which has insulin in it will not let me use it! This restriction forced me to leave work after two hours but the situation could have been worse like traveling out of state.
This issue needs to be addressed by Tandem as being a former ANIMAS pump user I could load up any amount I needed to treat my condition if in a pinch.
Of course if I had known this I would have taken two vials to work with me.
Anybody using the Tandem T:Slim X2 give them a call and complain about this unnecessary restriction to get them to send out an update. Thanks.


@Robert14 If i understand your post correctly you had +50 units in the reservoir after priming, etc. and you were unable to access the insulin?

  • If this value (the 50 units) was pre-priming, that is most likely your issue as Tandem thinks you need +45 units prior to use. That was most likely the case before the T:Lock was introduced, but is not currently accurate.
  • If this was post priming is there a setting that needs to be adjusted? I routinely run my reservoir to zero on day 3 or 4. When I attempt to extract any remaining insulin from the used reservoir I generally get <4 units.
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As @El_Ver mentions, with a regular syringe, the insulin can be extracted. This is a great backup which covers any number of situations where the pump is (for whatever reason whether pump, infusion site, battery, etc…) unable to properly deliver a dose.

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El_ver good day, just to clear it up I withdrew 65 units from my Novolog insulin vial and loaded it in the Tandem cartridge. After priming, the Tandem X2 pump notified me that the pump will not deliver insulin if it is less than 50 units upon loading it up for use.


How many units did you use in the priming?

With 23" tubing and the t:lock and not priming more than required, this would typically have been enough. But with very very little to spare.

If using the Luer Lock or longer tubing or simply being a little slow on the stopping of the priming, it would have been very easy to end up on the short side.

However with a syringe available as a backup, the insulin could have been extracted from the cartridge and injected as normal bolus as appropriate.


@Tim35, @Robert14 if I am understanding the issue correctly, the problem lies with the FIRST bolus after priming and the pump thinking there is insufficient insulin to bolus. Were it me, I would do a “Load cartridge” on the pump, add 10-15 units of Humalog/Novolog to the reservoir, and re-insert as a “new” cartridge. Then skip all the priming steps and set reminders. That way you can add a small amount of insulin to an existing reservoir and possibly “fool” the system by making it above an unmentioned threshold.

I have never tried as you describe but just wondering if it is possible to skip the priming steps? I thought the priming was required (as part of a cartridge change) and for the priming step, 10 units is the minimum for priming?

@Tim35, I prime about 12 units give or take 1 unit or 2. That fills the tubing when I see the drops. In the initial incident I should have had at least 50 units give or take after priming. The bottom line is the Tandem X2 insulin pump should not prohibit delivery of insulin if you have less than 50 units after priming. I could give numerous examples of having just enough insulin in the vial put it in my ANIMAS pump and use it. I dread having to go back to using the needle for a bolus.

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Are you sure about the 50 units? That’s my confusion here, because my pump just told me a few days ago that it needed at least 40. Maybe this is a software change?

Tandem claims that there is about 15 units of inaccessible insulin in a cartridge, but it my experience it’s been more like twenty Plus it takes 11-14 units to prime 23 inch tubing. If you were even just a few units shy of the 65 units you think you put in it, that would’ve put you out of functional range.

It sucks, but I think it’s just one of those growing pains you’ll get used to after a little longer with your new pump. I think we all agree that no pump is perfect yet. I love my X2, but I do have three complaints about it. That 20 inaccessible units is one of them. (As a new pumper, the insulin lost to the tubing was irksome, too, but unavoidable.) The minimum fill requirement is NOT a complaint for me. 40 units is approximately my total daily dose, so I’d never need to fill anything remotely close to less than that.

I’m sorry you had a bad experience with Tandem, though. I will tell you that they are VERY receptive to feedback. When I called about my first complaint, I was put through to two different levels of management and within a few days a member of the design team spent nearly three hours in the phone with me brainstorming about my complaint. I was really impressed with that. So by all means, if you feel strongly about this, contact them and work with them to find a better solution. Just be aware that this may be one of those unavoidable FDA requirements. I can’t see any reason why they would voluntarily set a minimum.

@Tim35 I add small amounts of insulin to an in-service reservoir and skip the priming regularly

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I should have better explained that as, your pump won’t even register 15-20 units. They just disappear. I’m not about to waste half a days worth of insulin, though, so I suck it back out with the syringe and add it to the fill volume of the next cartridge. Some wouldn’t agree with that since insulin does degrade over time and faster with body heat, but I’ve found the difference to be completely negligible.


I also have had this problem with my x2… is there any way to reduce the minimum amount the pump needs after priming to function? I use only 40 units for the entire three day span and often have issues with the priming process because of the 50 u minimum.

Good to know !!!

@bubblywhale you could fill more than you need for the 3 days and pull out the balance on the next change… Alternatively you could run the reservoir longer and just change the set. I understand the concern that many people have regarding degradation of the insulin. Maybe I have been lucky, but I have never experienced this (yet). I am also a thrifty (read: cheap) person and use things as long as possible to backstock a rainy day supply.

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Hi Robert. The Tandem does not allow less than 59 units of insulin. It will give the same error message the gentleman was speaking about

Thank you Antoinette

I agree with the original message/complaint. I also used my last bit of insulin to fill a new reservoir & by the time I primed & finished the process, it said I couldn’t bc it was less than 50 units. It’s 2:30 AM & I’m out & my tandem is beeping like crazy. I am an ex- Medtronic pump user & with their pumps, there was no mimimim so I had no idea. Very frustrating. When I was trained to use it, I could have easily been told pf this, but it didn’t sink in, apparently.
It shouldn’t be an FDA requirement since other companies can fill with less. Has anyone had any luck speaking to Tandem about this? It’s going to be a long night.

I hope you’re doing Ok. That’s frustrating! Do you have any long-acting insulin on hand? You likely already know this, but you can get by injecting a unit or two every couple of hours until you can get some more insulin. Do you have any syringes for this?

Since you’ve run out of insulin I’m guessing it’s due to economic circumstances. These are hard times but there are people who can help. Do you realize that you can purchase a 10 mL vial of Regular insulin at Walmart for about $25?

Please post an update. This is concerning!

Hi Terry - thank you for checking in and for your concern. It was more about my memory than anything- I thought I had another vial, or at least 75% of one. But, I only had about 15% of one & I didn’t realize that the Tandem T-slim doesn’t allow you to load a new cartridge with less than 50 units. Because it was the middle of the night I couldn’t get to a pharmacy & I live in a small town (no Walmart or 24 hour pharmacies available). So, I was just hoping maybe someone had found a solution such as a setting change that could make the tandem work with less than 50 units. It appears not. I will call Tandem to put in a complaint though. I see no reason for the pump not to load with less than 50 units when my Medtronic could do so. I ended up using a syringe to draw some insulin out of the cartridge I had already filled. It wasn’t great, but it helped. Once I fell asleep I went really high (have no long acting), but it happens. Now I know, make sure to double check that I have a full vial at all times! Thank you!

There actually is good reason for it. It’s all down to the accuracy and margin of error with the pressure sensors that determine how much insulin is actually in the cartridge. There’s about 15-20 unusable units left in every cartridge. You lose another 12+ units to the tubing (depending on length), and it doesn’t actually determine volume until 10 units of insulin have been delivered… That alone is 42ish units of insulin.

That said, you can actually remove the remaining 15-20 units of insulin (more, if the cartridge wasn’t “empty” when you changed it) and add it the next cartridge. Or heck, just add the last of you insulin to the existing cartridge.

You can also skip the fill tubing step if you’re reusing the old cartridge and/or tubing. Well, not technically, but you can trick the pump.

You go through the normal load process, but when you get to the fill tubing step, you can actually eject the cartridge just before pressing the “fill tubing” button. This is the tricky part, though. You have to watch the piston moving in and out to learn the right timing. After the screen registers at least 10 units, you can snap the cartridge back into place… BUT, YOU CANNOT TOUCH THE PISTON. If the pump feels pressure on the piston, it’s not the end of the world but you’ll get an error and have to start over. You have to time it so that you push the cartridge into position when the piston is fully retracted into the pump. It sounds more difficult than it is. If you pay attention to the sound, it’s really obvious when the right moment is. I actually seat the cartridge NEARLY all the way, so you only have to give it that final snap into place when you hear the brief pause between piston movements.

Between reusing the remaining insulin and the old insulin-filled tubing, that should give you an extra 30 units at least. The 12ish units in your tubing won’t help with the detection of the minimum fill, but it will give you 10 extra units for when you’re desperately low on insulin.

Of course, none of that is as ideal as keeping well-stocked. It’s scary moments like this that make me a supply hoarder!

Do you have an emergency backup plan in place? Once a year I get a new bottle of Levemir or Lantus, whichever is preferred by insurance at the time. The prescription literally says “use in case of emergency only”. It lives in the fridge solely in case I have pump failure or otherwise can’t depend on the pump for insulin delivery. Of course, I’ve always got insulin syringes, too. They travel with me everywhere I go for short term emergency use, in case I have to pull insulin out of the pump.

If the cost of something like Levemir/Lantus is prohibitive, especially for something you’ll hopefully never use… Like @Terry4 mentioned, you can buy the old types of insulin at Walmart real cheap. $24.88/vial last time I bought any at the start of the pandemic. R is the short-acting and NPH is the long-acting, but they’re not equivalent to modern insulins. You really need to pay attention to your blood sugar and eat when you’re dropping. It’s not the same at bolusing when you eat. I actually used the premixed 70/30 of the two before I started pumping. Was just easier for me.