T Slim software fault - Bolus Failure

So I got my first insulin pump just over 2 weeks ago (a Tandem t slim) and am now back to the old dmi regime thanks to 2 faulty pumps and no solution yet in site.

The first pump did fine for the first 48 hours but then it suddenly beeped and came up with a warning screen telling me that the bolus it had accepted 2 minutes earlier had not been delivered! As t slim users will know there are a total of five screens to be got through before the final screen appears (looks like a water droplet) indicating that the bolus has been accepted and will be delivered. I had gone through each screen in turn including the calculation screen which shows Onboard insulin, active time remaining, carbs consumed and blood sugar level input - it asks if you want to check the calculation or you can just press the tick button.

In other words the pump is aware of every required aspect and has approved a bolus based on all those details, BUT, not 2 minutes later the same pump, working on the same information changes its mind and refuses to deliver the required bolus!

The first time this happened I was astonished to learn that the uk technical support were not issued with a real pump for diagnostics!!! All they got was the app which is why they kept asking me had I completed both screens and couldn’t understand when I kept correcting them because there are 5 screens to complete.

Anyway, in the end because they had no way of telling me if the bolus had actually been delivered or not I asked them if it was safe to continue using the pump tp which they replied that they could not advise me about that and I should speak to my doctor.

This was late afternoon and there was no way to contact the doctor till the following morning so I removed the pump and went back to injecting.

I was contacted the following day and asked if I would install a completely new setup to see if that would cure the problem - new cartidge, infuser, etc. I agreed but because I now had Levmir in my system had to wait till the following day to do this.

Same result!!! Pump worked fine for 2 days then threw the same warning about bolus not delivered! Talk to Tandem; disconnect pump and back to dmi - what a great life!

Now they have another idea - maybe it’s not the pump; perhaps it’s the infusion kit! So they send me out another box of infusers and off we go again.

Same result - pump does fine for about 2 days then throws another wobbly! Exact same as before.

So now they send me a replacement pump and guess what; yep, it works fine for 2 days then throws up the same “Bolus not delivered” as the previous pump.

I now have no confidence in the pump. Before I retired I had qualifications in software programming and there is no doubt in my mind that there is a fundamental sotware problem with the pump that currently renders it unfit for purpose (as defined by the uk yellow card scheme for faulty medical equipment).

The are going to phone me tomorrow to see what can be done to resolve the issue, however I have stated to them that the last fortnight has been hell for me physically because of the repeated stop/start change of insulin regimes I have had endless stomach pains and diarrea, headaches and nausea. I am not prepared to continue being used as a fualt finding guinea pig. I am prepared to give the new G6 model a try because it has a software update which may have resolved this problem, or I am giving up on Tandem and raising the issue of “fitness for purpose” under the uk yellow card scheme.

I’d be very interested to know of any other t slim failure to deliver bolus that you may be aware of.

Sorry this has been so lengthy but I really needed to blow off steam!!!

Anytime I have had a failed bolus it was because of my infusion set.
You mention you get two days, then it happens.
Have you tried changing your infusion sets every 2 days and see how long it lasts?

I discussed this in some detail with the tech guy who ruled it out because he said it would have come up with an error code indicating an “occlusion? fault”.

I am very interested in your having experience of this, can I ask did you simply change the infusion set and continue using the pump? Did this resolve the problem?

Your right about the occlusion fault message.
But it sounds too similar to that issue, across multiple pumps, to at least not try this approach.

I’ve only ever had one failed bolus and it was due to the infusion set, it did not give an occlusion error alarm though.

It sounds like it might be an issue with your sets, especially since it’s been after two days. Have you ever noticed droplets or condensation inside the plastic area of the set? That happened to me a number of times when I was using a 6mm cannula set, but stopped altogether when I switched to a 9mm set.

Some people may heal more quickly and have issues with absorption which a cannula set. A steel set may work better in this regard especially if you are lean or active.

If you are from outside USA (OUS) which I believe you said UK, bear in mind the software and screens you have on your Tandem t:slim X2 are not necessarily the same as what USA customers would see.

Also be aware that Tandem provides direct Technical Support for USA and Canada. All other International areas are not covered directly by Tandem Technical Support.

When I first switched to Tandem after using only Minimed/Medtronic pumps, I had the same problem. A bolus would start delivery and than I’d get the drop delivery alarm. I finally called my trainer and we meet up and looked at different infusion set.
I made the switch back to metal infusion sets and haven’t had one alarm. I don’t know the technical issues of how fast or slow insulin is infused, or if a smaller basal rate might be an issue. All I can say is, that one changed fixed the problem and I haven’t looked back.
Most times (not all) a pump issue is the infusion set. Good luck!

That’s an area I shall certainly explore - being a first time pump user I have no experience of different infuser sets and it is the 6mm cannula set I am using with every failure. I shall ask about this tommorow - many thanks.

I wasn’t aware there were screen differences between countries. You are right about the support but I just think of them as Tandem as when an error code came up on one of the pumps they said they would have to refer back to the US guru and because of the time difference it would take a while to get back to me.

Many thanks for that info - I am certainly going to persue this with them because I have to say that when the pump is behaving it really does control my levels way outside anything dmi can produce!

Maybe check this UK forum.

I cannot get the 30 degree sets to work more than 2 days for me.
Same goes with the 90 degree sets with 6mm cannulas. The 9mm 90 degree sets work great for me though.

I wasn’t getting errors but noticed what I though was condensation inside the plastic housing and based on someone else’s post in the forum figured out it was insulin which explained the lack of sensitivity to insulin.

I switched to the 9mm cannula and have had zero issues since and insulin is working as expected. I started using the Tandem pump in January and have been very happy with it, even more so with the 9mm cannula.

I do think that they should provide new pumpers with samples of all the infusion sets available rather than just giving you a single type when you have no idea how it’s going to work for you.

Actually, this is where the company rep comes into play.
I called my Tandem rep, and he sent me out a goody bag of almost all the different sets for me to try out. NO COST! That is how I ended up finding the right set.
Btw, I like the steel sets, but really dislike the two points of attachment with a loop, etc. Not entirely sure why, but it really bugs me. Otherwise I would just use the steel sets.

This site has been a mine of information for me! As I said this is my first pump and I just assumed that everything worked straight out of the box. I was only shown how to use the 6mm cannula set up and no mention of any potential problems.

So, I have now re-attached the pump and changed the infusion reminder from 3 days (default setting) to 2 days. So far the pump is doing great but I shall be raising the cannula issue tomorrow and asking for a supply of the 9mm sets.

Many thanks to everyone for the input - it is very much appreciated!


I agree completely with talking with your rep or trainer. It is their job to make sure we are happy. With both pump companies I have worked with, I have just called my trainer/sales rep and we have been able to meet up and talk different infusion sets a number of times over the years.
And when you have that relationship with your rep, things can happen quickly. I have had someone drop an item off at my front door because someone with the company was in the area. Or we can meet at the house after they finish with another patient in the area, or meet at a local coffee house to play with infusion sets.
That relationship with your rep is kinda like your relationship with your doctor. Thy are part of your team and need to help you find the best fit for you, not what the company wants to push.

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