Insulin Gone South?

I’m wondering if anyone has had a similar experience with insulin as have I: toward the end of a bottle of insulin, it starts to lose its effectiveness. I am very careful to only use a bottle for 28 days and then discard it. But towards the end of that period, right before I start a new reservoir for my Medtronic pump, my blood glucose goes up. Anyone else have this experience?

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Hey @Denise0730, which insulin are you using, and how long does a reservoir last for you?

Our experience with Humalog doesn’t match yours, but there are many factors at play here. For instance my son keeps an entire semester’s of insulin sitting at room temp in his dorm room with no issues. We have had some issues when he was younger and a reservoir lasted for 6 days, but I think a lot of that had to do with the insulin interacting with the plastic in his Tandem reservoir.

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Hi Chris. Thanks for the reply. I use Novolog because it is reported to be a tad more temperature stable, which is important in the southern California summers, where I live. I store my insulin in our wine fridge because its easier to prevent the insulin from getting too cold and it doesn’t take up needed space in the fridge’s vegetable drawers. I use only about eleven units of insulin per day. (I was born with only one kidney, so my body isn’t producing as many anti-insulin chemicals.) i believe the reservoir holds 300 units, but I only fill it with about 50 units—some extra just in case of earthquake or some other disaster. I’ve been Type 1 for over 55 years.

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I consider switching from Fiasp to Novolog quite frequently. Think I will give it a try but am not quite sure about the transition. Very insulin sensitive, even after 50 years!

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I have observed the same phenomena for several years. It is easier to notice if you consider your TIR for the week/pump refill. I am on a Medtronic, 3 ml cart, and observed this for both Humalog and Novalog. The first and second refill ( 6days) my dex readings are 83% TIR. The third pump fill around 12- 13 days after opening a bottle the activity seems less, and TIR drops to about 60%. If I inject the insulin it seems active (a crude test of activity. It does not matter if the vial is refrigerated between pump refills or not.

I have termed this premature expiration of an open bottle of insulin. It appears similar to insulin resistance, as well as a site going bad. I get my insulin quarterly, and have had no issues with the pharmacy or time refrigerated. It would be good to know if this is just a pumpers phenomena, or if MDI see it also.

Mike

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Hi Mikey417,

Sorry for the long delay in getting back to you.

I discussed this with my diabetologist and she suggested changing my infusion set every two days the second half of the month. I’ve been doing that and it does help keep my numbers in line. Of course, it means another poke, which I’m not thrilled about, but considering the number of injections I’d have to take, I’ll live with it. Another problem, though, is that I’m a rather small person, so I don’t have a lot of real estate for changing every two days through the second half of the bottle. But, it is what it is.

It would be good to hear from people who take multiple daily injections on this topic. Or other pump users . . . . Any one care to chime in?

Denise

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Denise,
I also have changed my inserts more frequently once it goes south, it helps a little but the difference of TIR is dramatic. Why would changing every two days, as opposed to three, be better for insulin activity from a bottle open > 2 weeks?
I have also continue to use inserts after refilling the cartridge. So I know the site works, and the insulin activity is still decreased.
Again, it would be good to hMikeear from others.

Hi Chris,

Sorry for the late reply on this. I use Novolog and was changing my reservoir and insertion set (Mewdtronic 770G and Guardian 3 sensor) every three days. I use, on average, about 11 units of insulin a day.

My diabetologist suggested changing my set every two days, instead of every three days, but that does not seem to have made a different. I am advocating for using a bottle for only 14 days instead of longer, since it is at day 15 that my numbers start changing.

Denise

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