T Slim Bolus Occlusions since T-Lock

I’m wondering if anyone else has had many Bolus Occlusions since T-slim went to the T-Lock.! I have had many. I have decided that it may have been caused earlier from over filling the cartridge. I got along for 3+ years putting over 300 mL in a 300 mL cartridge. When T-Lock came, the cartridge seemed to be more resistant to accepting so much. and that’s when I started getting occlusions. I have since been putting in 300 or less, but still get quite a few occlusions. It depends on the cartridge. The cartridge I filled yesterday, would not accept even the 300, and I am getting occlusions with all of my boluses. I’ve talked to support many times over the past few months. Pump is now out of warranty.


None that I know of.

We generally fill 180~200 units.

We use the Tandem t:slim X2 with Fiasp.

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I’m not sure what the T:lock is so this won’t be particularly helpful, but I have watched the Tandem idea on filling cartridges, and they say on there that overfilling the cartridge can cause problems. I have been filling to 250, and so far so good.

I know this is not helpful. It’s okay to have nothing to say in response. :grin: I look forward to seeing what others say.


Tandem (relatively) recently changed the connection in the tubing from a leur lock to properitary t:lock.

It is important the the infusion set and the cartridge both use the same type of connection.

Any supplies received at this point in time (for Tandem) should say “t:lock” on the outside package of both the cartridges and the infusion sets.




@Bill when I first started with my TSlim I would max out the reservoir, and occasionally get occlusions, about 2 a month. Now as my. TDD is lower I don’t load as much, and have 1 to. 2.occlusions per year. I have always had tLocks, so I am not able to speak with any knowlesge about the Luer lock days.

I also found that when I started using steel. Sets exclusively that I had fewer problems overall.


Thanks all. i see now that cartridges are 3 mL and not 300 mL! thanks for letting that slide! I’ve decided it has been caused by me pushing the limits, or I’m still experimenting to see if its the first fill from insulin out of fridge. Maybe i’m not letting it warm up enough ?

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I used to fill the t:slim cartridge with a full 300 units and didn’t get occlusions. But I can’t rule out that maybe something has changed in the t:lock era that’s causing a problem.


@Bill 1.thing that I do that IMHO helps, is draw the air out of the reservoir several times before attempting to fill. I use a completely empty syringe (before I load with insulin)


Same. (Almost). I extract air from cartridge (once).

Then fill syringe with 180~200 units.

Then extract air from cartridge again with syringe that contains insulin. Pull syringe back to about 300 and let any remaining air bubble up into syringe. I do not remove the syringe from cartridge at that point but just let the small amount of air sit at the top of the syringe. Then push insulin from syringe into cartridge. The air bubble at the top (of the syringe) is never big enough to be pushed into the cartridge.

Once I inject the insulin into the cartridge, I am careful to always keep the cartridge insulin port pointed up so as to allow any remaining air bubbles in the cartridge the greatest possible chance to move to the top such that when the tube fill process runs (We use 12 units for tube fill) there is a good chance for any small remaining air to be removed at that point.

I try to be balanced in my approach with air and filling the cartridge.

I don’t want to be obsessive. But also I don’t want to ignore it. So I try to take reasonable precautions.

NOTE: Often times people not on the Tandem ask about how long it takes. Apparently this is a “make it or break it” for some people on the Medtronic. If this is a huge deal then certainly it is good that Medtronic offers an option from the Tandem. Personally I don’t care how long it takes. We do this once every 2 or 3 days. In any event, when I timed it, it took six minutes in total.

I never rush the cartridge fill process. I not only want it done right, but I also do not want to second guess myself later when we have any of those mysterious issues where something is not going right and we are trying to figure what is wrong.


Wow. That is quite long… I can see how people used to a 30-second cartridge change process may not like that!

I know that Tandem uses a bag-type thing inside their cartridges. If you’re drawing air out, is there any risk of accidentally puncturing this bag thing?


Options are good. What is trivial for one person is a deal breaker for somebody else. And vice-versa.

No. The Tandem produced video on how the insulin delivery works is nice. Really explains the entire concept. Without watching the video, I can not imagine it would make any sense. The vide is very short - only 41 seconds but instructive. Not about cartridge fill but rather about insulin delivery.


empty full bag%20connection no%20bag

I decided to tear into a cartridge. After I took the “lid” off, I filled with 3 mL of water. It was pretty full and not much room left in the “bag”. I bet its really tight when the “lid” is on! No way can needle puncture bag!


@Bill, these are great pics: enlightening!

I cannot contribute anything to your question. I do think, based on the info in this thread, that your conclusion is likely. Here is hoping that you will see less occlusions in the future!