Infusion Set every 3 days - T:Slim cartridge every 6 days?

Is there any reason to change the T:Slim cartridge with every infusion set change? If I fill the cartridge to 300 (280 after fill) Units I can easily make it last 6 days - or every other infusion set change. This would save on time and money.

I would just change the infusion patch and connect the existing tube/cartridge to that. Does anyone out there do this?


During training our rep told me “off the record” this was something I could do for my son. I haven’t yet because we have more cartridges than anything and I like to keep my supplies on an even keel but I think I’m going to start. It will save us 40 units of insulin every 3 days which is more than 2 days extra use for him. Right now I put about 100 units for 3 days and I could use only 160 for 6 days. Seems logical to me.

I do! Let cartridge change go until low insulin warning. Sometimes changing site before cartridge. A lot of folks change independently of the other.

Heck yea, I’d do that if i could! My kicker is my basal rates- my daily rates use more insulin than all of my daily boluses combined!

Shouldn't basal be about 50% of Total Daily Dosage (TDD)? Maybe you need to lower your basal and increase bolus?

I've been pumping for ten years on Animas and Tandem and always changed independently. I always fill the cartridge all the way, and only refill when it's empty (or maybe <10 if it would go empty overnight or while I'm out). I change the site when I feel the need to (2-4 days). It means that I have a few unused tubes, but that's much better than wasting insulin and cartridges.

I thought about that, but my dietician had me set it at 1 U/hr overnight, and 1.4 U/hr at peak time between 8 am and 5 pm. I usually use 30 units at the most per day for all boluses (About 10 U per a meal). Total daily basal dosage for me is around 27.6, so I'm using about 60 total units a day. I agree though, when I first entered them, they were way above my personal calculations. However, I am still working to figure out where changes can be made.

I’ve been doing that for years. I have to refill every day and a half, but infusion sites can go for up to three days. My cgm lets me know when the site is starting to fail, so I change that out whenever it’s needed. Simple stuff.

Cartridges I generally underfill slightly now and let last for 6-7 days. I have tried 8-9 days when filled completely (and was trying to "eat better" too so required less insulin) and got an occlusion that wouldn't clear so I'll probably keep to 6-7 days and avoid any more than that.

But I'd say that if the insulin can last you the length of time of two site changes then I say there's no reason not to let it.

That's half the reason I chose the t:slim(though there are other 300 unit models available)... less futsing with stuff on a day to day basis. Sure the cartridge change itself is longer than others, but not so bad when it doesn't have to be done too frequently.

All the time! My TDD is low so I can get close to two weeks on a cartridge before I run low on insulin. Have not seen a drop off on insulin quality. Just change sets as I need to, usually about twice a week.

1 Like

Just saw the trainer. The trainer said I could change the cartridge after 6 days, but change the infusion set every 3 days. Specifically, in 3 days insert a new cannula and move the old tubing to the new cannula. In 6 days, take everything off, fill the new cartridge, new tubing, insert the new cannula, fill the new cannula and get going. Repeat forever.

1 Like

"They" say that after about three days the insulin is no longer any good being it's been on, close or next to your body. That it isn't as effective. I just change it out because I hate having a mixed matched number of insets vs tandem boxes lol.

Not always. You can have a 60/40, 50/50, or 40/60 basal/bolus split. I err more on the 60/40 split because I need more for basal than I do for my food.

Depends. As far as I know, Novolog insulin is approved in insulin pumps for up to 6 days (I used to do this all the time with other pumps), but lately I've noticed in the t:slim that my insulin doesn't seem to be as potent after 3-4 days for me.

I’ve only ever changed everything every 2-3 days, but if I leave the cartridge what process do you use to refill it with insulin?

I will fill my cartridge full and run it till it’s empty. For me that is about 10 days. I do not notice any degradation of my novolog over that time. I do change sites 2x a week so every 3.5 days.
I do keep my pump in a Frio pump wallet and it always stays cool to the touch.

I just started on this pump and had this issue. However, I think we put in a whole lot more insulin at my training than I ever use, and I did let it sit there for way more days than I normally would (like 9). They do suggest only three days, I am now doing five or so with no issues. The nine was too long…I probably used one cartridge for six to seven days with my Ping and my Medtronic.

First time poster here,

How are you guys getting more than 3 days of insulin use with your tSlim?

I was on a Medtronic for 12+ years and could easily go 6-7days on one reservoir of 180u in my pump. Insulin was fine for the full 6-7 days. I used Novolog. I would switch my infusion site if it became itchy or loose. But, most of the time I could go 6-7 on the infusion site as well with no negative effects.

Now, I switched over to the tSlim and I am lucky to get a full 3 days before the insulin seems to “go bad.” Still using Novolog. I have tried leaving insulin in the cartridge in the pump and just changing my infusion site, but that does not help at all. Unless I do a full cartridge, tubing, and site switch, my blood sugar will spike right at 3 days and not come down no matter how many boluses I give. It just levels off and still slowly rises over the hours.

Once I change the cartridge, tubing, and site, my blood sugar comes back down to normal with the next bolus.

I am using the same type of infusion sets with both the Medtronic and the tSlim.

I have been trouble shooting this for about 6-8 weeks and have not had any success in figuring out what the difference is between the Medtronic setup and the tSlim setup.

I am about ready to give up on the tSlim and just go back to my Medtronic due to the frequent site changes, waste of insulin, and ultimately waste of money.

FYI, the Dexcom CGM that I am using in conjunction with the tSlim rocks!

Thanks for any help!



I am having the exact same issue. Was getting 6+ days with my Medtronic. Can barely get 3 days with my tSlim.

Did you ever figure anything out?



You might try a different infusion set. Quite a few t:slim users report using less insulin after switching from other pumps. When my daughter had issues the first few weeks on the t:slim, tech support insisted we try different sets.