Using Novolog with T-Slim(?)

Hi - I’m new here and I couldn’t find any related topics so here goes:
I switched to the T-Slim in November 2014 and have had nothing but drama. Within 2 weeks my BG was hovering in the 200 range; often spiking up to over 300 after meals. Forget about my “morning phenomena” - ridiculous in recent weeks!

Tandem’s Customer Service was really no help. They offered no advice (since they’re technically not allowed) and all they did was go through the standard safety checks.

Not sure how many of you do this but since the T-Slim wastes SO MUCH insulin I’ve followed my previous practice of pulling unused insulin back out of the cartridge & putting it back into the vial. I’ve been doing this since first starting on pump therapy in 1998.

I started wondering if there was something wrong with the insulin so on a recent changeout I decided to use the brand new vial of insulin, fresh from the pharmacy. I had switched back to my Animas pump since my levels seemed just a tad better while using it. Within only one day my BG was way down - back to normal. I had lots of adjusting to do…

So I’m still using the new vial with the Animas pump because I’ve read in 1 or 2 other places that people were having similar high-BG issues using Novolog with the T-Slim. I Googled “T-Slim with Novolog” and found a couple blog-posts & comments on this.

Anyone else having the same problem? Does anyone else “recycle” the leftover insulin from the cartridges?


Welcome to the site. I’ve never use the T slim and I’ve always wanted to Medtronic since 1995. So I really don’t have a clue about why your blood sugar is would be so high and I have found that reusing insulinfrom old cartridges is a great way to save money. I’ve been doing it for as long as I’ve had my pump about 20+ years with no problems.

I find the biggest problem I havewith Medtronic when I get highs is that it’s the infusion site or the infusion type that I use are you several different ones on the kinds of activities I do so maybe that has something to do with your T-slim.

I am a member of this support group where I live and there are about 20 type one diabetic’s using pumps who are in the group. Several of them have tea slams and say they love it but that’s about it.

Maybe being so frustrated with your tea slam and switching back to your old pump with a brand-new bottle of insulin reduce your stress level. Stressed raises my blood sugar faster than anything I could eat!

I hope some people who actually use T slim will give you some better answers.


My first pump was a Medtronic - the one where you shut the cartridge inside a door and there were these little doohickeys that you had to align with your cartridge level. :slight_smile:

I get what you’re saying about sites and stress but I’ve never, ever been unable to control my BG like this. Even when I had the flu last year - it was challenging but I managed. Believe it or not the only time stress affects my sugar is when I’m so upset I bawl my eyes out. That sends me sky-high sometimes.

Certain sites are less effective than the abdomen - when I use my upper glute area my sugars tend to run a tad higher but nothing even remotely close to this. I’m pretty good about rotating my sites.

I reported this occurrence to Novolog & they are sending me a replacement bottle. They offered to take the old bottle back & give it a visual inspection. They don’t test it further than this. I filed a report with the FDA as well, on recommendation from novo nordisk. I also sent them an email to ask about testing the old vial I saved.

We’ll see what happens… Thanks for replying!

I have been wearing a Medtronic Paradigm pump for about 15 years and have had no real trouble with it. I have had T1D for about 58 years and am a 50 year medalist with the Joslins Diabetes Research Center in Boston. I have been looking for web sites where I could communicate with people who have had type 1 along as I have. It this a good site for exchanging help tips and just finding some friends who know what we go through every day? Thanks, Lisa


Congrats for 50+ years!! I’m on 43 years and counting! Got my 25 year Joslin last year!! Have you tried They ask a lot of questions … sometimes interesting!

What have you done to rule out each component that could be causing the issue?

For example - could you have a bad batch of cartridges? (Do you have a different lot number of cartridges that you can test out? If these work better, it could indicate that the other lot number is a problem)

When your BGs are high and don’t come down by bolusing through the pump, do you attempt to bring them down with an injection/shot of NovoLog instead? (If this works, it’s definitely not an issue with the insulin, but if this doesn’t work then the insulin seems like it’s the problem)

Have you tried changing the type of infusion set you use? Some people’s bodies simply don’t jive with certain infusion sets. Something as simple as changing what kind you use can solve so many problems.

Finally, how often are you attempting to change your basal/bolus rates to compensate for the highs? I’ve switched pump brands many times and while it doesn’t seem to make any logical sense, it’s true: you sometimes have larger or smaller insulin needs depending on the pump. This doesn’t mean your control is bad or that there is even something wrong with the pump! This has a lot to do with the speed with which bolus insulin is infused by the pump and in what amounts/how often basal increments are delivered.

For what it’s worth, recycling the insulin from the old cartridges could be the issue. With ALL pumps, it’s technically not recommended. Some people can do it successfully…others find it to be problematic. All cartridges are made of plastics which can, over time, degrade the insulin. That’s why it’s recommended you only use them for 3 days at a time. Taking that insulin out and submitting it to ANOTHER 3 days can degrade it to a point it’s really lost a lot of potency. I used to do it with my t:slim, but then I stopped. It wasn’t worth not knowing whether my insulin would work or not for the next few days.

I had switched back to my Animas pump to see if it was something to do with the T-Slim itself. There was no difference.

Then, I opened a new box of cartridges and used those. Still no difference.

Second and third bottle of Novolog and still no difference - note that I originally mentioned that I do as many other pump-users do and recycle the unused insulin from the “empty” cartridges and put it back in the insulin vial. (I tend to fill a new cartridge first and then deal with the old one.)

My doctor advised me to be more aggressive in raising my basal rates and overestimating my boluses to “shock” me back to low for a couple days. He advised me to try to keep it as low as possible for a day or two. He thought this would fix my insulin-sensitivity. This didn’t really work either - very temporarily.

I gave up on Tandem customer service since they had no help for me after calling them at least 3 times and giving them serial numbers off the boxes of cartridges. They had no information to share with me.

I have used the Inset-30 infusion sets for the past 5 years with NO problem. I used them with the Animas and they are similar to the Silhouettes I used with my last MiniMed pump.

I understand that your basal rates can vary slightly from pump to pump but they should NOT go from a total of 11 basal units per day to over 26. That is just ridiculous.

I have had NO other problems with my new vial of Novolog (unadulterated since I am not currently using the T-Slim). I might try to go back to the T-Slim but would you blame me for being wary?

I do not want to go through the same thing again and I want to have that older vial tested.

*Just a follow-up notation that on my NEW vial of insulin I am back down to under 16 total basal units per day and I am still running very hypo a few times a day. This has been very frustrating since I have no answers, really, other than that the insulin I was using was rendered significantly less effective for a total of over 3 months.

I plan to look for an independent lab to see if I can get the vial tested.

I recently switched from Medtronic to TSlim and I use Novolog. When I started TSlim, and I switched to the Inset 30. I was having issues with highs, so I switched by to my Medtronic Silhouette. I’m back to normal now. I am thrilled with the TSlim so far.

I share your interest in not wasting insulin, but the way I understand it, once it goes in the cartridge you should consider it already used.

When I’ve asked trainers, product reps from different pump manufacturers, and even fellow members of the San Diego Insulin Pumper support group, the answer’s always been the same–the plastic that holds the insulin in the pump interacts with and degrades the preservatives in the insulin. (The same degradation takes place if you pre-draw insulin into plastic syringes and leave them for a coule of days.) By drawing degraded insulin back out after 3 days and putting it back in the vial, you are ruining the rest of the insulin remaining in the vial as well.

One pump manufacturer that I know of uses glass cartridges (similar to what the insulin pens use) instead, but that leaves you with one more possible point of failure.

The unused insulin in discarded cartridges just seems to be one more of the many costs of pumping insulin.

I know I am super late but I use the T Slim with novalog and I found that my cartridge will last 3-4 days and If I need to change it before then I will pull the insulin out. The customer support is generally amazing, I had an issue with my pump at 2 am and they spent 30 minutes on the phone with me fixing it. Sometimes when i am high it is cause of the infusion set I am using.