Trouble with Tandem cartridges?

I’ve spent the past 24 hours trying to trouble shoot a weird and persistent load problem with my Tandem t:slimX2. After a frustrating hour+ spent with a Tandem tech who wasn’t listening to me (unusual - usually Tandem’s tech support is quite good), he finally discerned that I’d actually done everything exactly right, including removing air bubbles, we landed on ‘may be a faulty cartridge’. I’ve used a pump for 21 years and a Tandem for the past 5ish and have not had cartridge problems in the past. I’m wondering if this is a more pervasive issue others are seeing.

I’m prepping for a trip out of the country and wonder if I should take more extra supplies than usual, assuming that some portion may be faulty.

Thanks, Kristin

It’s probably just a freak event but it wouldn’t hurt to take extra supplies - ideally take some cartridges from different boxes/lots if you can.

Hi Kristin @Guildk, has this issue happened with more than a single cartridge? And, can you briefly describe the issue.

I’m just started my 5th year with the t-Slim x2 and have not yet experienced any problems with cartridges. A few times after purging air from the syringe and reincerting the needle into the cartridge, I can’t pus insulin into the cartridge; U need to “fish” about and find a pot under the white rubber that will allow insulin in. Once I succeed pushing in the insulin in all is well.

I set my pump alert to notify me when I reach one day supply in my active syringe and pick a relaxed time to prepare the next; the “ready” cartridge fits nicely into the box aling sude the vial.

@wadawabbit Thanks for the suggestion to try to pull cartridges to take on my trip from different boxes and (hopefully) lots. That’s a good strategy to minimize impact from any manufacturing defect.

Hi Dennis @Dennis -

I’ve had those same full issues you describe and have always been able to work through them. This was something new.

It started with my pump requiring me to repeat my fill tubing process. I’ve had that happen before when I’ve hit the wrong button, but could swear that didn’t happen in this case. After again filling my tubing with the additional 10 unit minimum required, I got a message saying that my cartridge needs at least 50 units at refill. It should have had at least 85-90 units at that point, so that was puzzling.

My pump wouldn’t let me get out of that screen without saying yes to adding more insulin to the cartridge. I added another 100 units to be on the safe side, in case somehow there was actually <50 units remaining in the cartridge. And I again refilled tubing with the minimum additional 10 units into the sink. And again got the ‘must have 50 units’ error message.

At that point I wasn’t going to add more insulin, but my pump would let me get back to ‘full tubing’ then and so I tried that one last time. At that point it let me complete the process.

In the morning, I was surprised to see my pump saying that there were 37 units of insulin, rather than the 155 that I estimated. That’s when I called Tandem to report the issue.

Unfortunately my hour on the phone with the Tandem tech today didn’t give me confidence that any actual problem assessment was happening. Or stop the weirdness. Now I’ve just noticed that it’s been stuck at reading 115 units for 3 hours. I’ll call Tandem to report this and change out the cartridge, trashing another 100+ units of insulin.

I hope that all of this is tied to this one cartridge, but given that I’m traveling in about a week, I thought I’d throw the question out there to see if there are recent reports of manufacturing problems with pump cartridges. If you haven’t heard of cartridge problems, that gives me greater confidence that this may be a fluke.



Hi @Guildk . If you’re not satisfied with the tech support you’re getting you can always ask to speak with someone else. Thankfully your prior experiences were good, but this rep apparently needed more training, or you needed a higher level than he was able to provide.
It sounds like you’re now using the cartridge you ended with when you finished the call, but that mis-coint of insulin is concerning. If it were me I would try another cartridge - one from a different box/lot number.
If it happens again I would tell tech support and say I have concerns about whether the problem is with the actual pump. Pump replacements usually happen quickly once you’ve made an acceptable case.

Kristin @Guildk, you have pointed out a weakness in the t-Slim pump software - the inability to accurately, or even closely, count the amount of insulin in a cartridge. More later about this.

To be on the “safe side”, I suggest that you may want always to begin a cartridge change with at least 100 units [1 ml] insulin and avoid the message “not enough insulin”. NOTE THAT THE CARTRIDGE NEED NOT BE CHANGES EACH TIME THAT YOU CHANGE THE CATHETER / CANNULA, just remember to fill cannula, That process works well for me now that my daily need for insulin, even while eating 230 grams of carb is only 20 units. Also note that when your t-Slim shutd down and indicates that the cartridge is empty that there are at least 10 - 15 units that can be extracted with a syringe and used for “emergency” injections.

Your pump scale reads “37 units”. when I know that, after tubing fill, I have at least 100 units, my pump reads 60+ - the next day it miraculously multiplies to 80 units. Crazy. Rather than relying on the pump volume meter, I try to remember when I added insulin and prepare ahead for when I need to change the cartridge - this information is in the pump history.

I hope your travels are enjoyable and free from diabetes “worries”; do pack sufficient supplies in your carry bag for the duration, and backup in checked bagage.

Ruth Clevenger - my pump trainer said minimum fill for the cartridge is 100 units, and to fill the tubing with 11 units for the pump to register a proper fill. She said the face of the pump says 60+ units until 10 units of insulin of insulin has been given, then it will show actual units remaining. Best wishes on resolving this problem and a safe trip.

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Thanks for all the suggestions.

For anyone who comes across this thread seeking cartridge guidance, next time I’d start over with a new cartridge right away when the first erroneous ‘must have at least 50 units to fill’ came up. I’d initially filled with 110-120 units, so even after having to fill the tubing twice that math made no sense.

Hopefully it was just something with that one cartridge. It’s reassuring that I didn’t hear through this forum that there have been more widespread problems with cartridges.

Thanks again!

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