Bad insulin

I had a colonoscopy on the 13 of January. Ever since then my blood sugars have been erratic . It seems to be staying elevated more often than normal. I tried changing my site, I even tried increasing my bolusses and it still seems to be happening. Then I got thinking about the last time I changed my insulin in my pump. That was January 10th. Could my insulin had gone bad or less effective?

Are you saying you’ve had the same insulin in your pump for 9 days…?

Insulin usually doesn’t go “bad” unless it’s been exposed to really extreme temperatures.

Yes, I know. I have been at my wits end trying to understand why my bloodsugars are staying high after eating, despite increasing my bolusses and exercising. I had a colonoscopy on the 13th and figured that was the reason. IDK. My site wasn’t the issue. On top of all things my sensor needed changing yesterday. I went through the warmup did the calibration and I got a message telling me to wait to calibrate. So after 15mins I gave my pump another bloodsugar reading and that number was rejected also. The numbers were all in range. So I had to change that sensor. Sensor number 2 did the same thing. I went on the Medtronic replacement site to replace the failed sensors and today I got a call from Medtronic. The lady was difficult to understand. I explained the same thing to her and she had the gull to ask me if I needed training. Give me a break!!! I have been doing this long enough that I know what to do. She’s lucky I didn’t hang up on her!! I have no idea why those sensors failed. Sorry I exploded on you. This is really bugging me! :disappointed_relieved:

'possibly it’s just that the planets are not aligned or it could be coincidence that you got a couple bad sensors in a batch (i have).
as far as high glucose after a procedure i just look at the STRESS involved. i just had a stapedectomy (ear bone replacement) and after a week i’m finally getting down into range. it was mostly about being stressed out and the meds used for the procedure. (with steroids it’s a real crapshoot)

ps yes some of the Medtronic’s folks are difficult to understand…you can always call back to get another rep

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I know what you mean by “being under stress”. When I lose control it is a really awful feeling. My bloodsugarsmore typical for what they were before. I actually went below target after my lunch bolus. I eat the same way at lunch. I am blaming the highs on my insulin being bad. BTW, I am happy for you to finally be back in range.

Life with diabetes is definitely not easy. Sensor issues make is so much harder.


It could be the insulin in the pump. Insulin degrades in a pump. It’s usually constantly near your body heat, plus I gather being in a plastic reservoir degrades it too. 9 days is a long time to be sitting next to a 98 body temp in a plastic container. Some people notice it doesn’t work as well after 3 days, my old endos office, the NP was a type 1 too and she used to say she could tell the difference on day 3. I don’t think she was telling me to try to just make sure I changed it out as I was/am on Omnipod and you have to change it. But I have heard that from others too.

Nowadays if the question comes up I just change out my pod. If it’s the problem it solves it, if not then I can move on to figure out what else it might be.


I never gave it much thought, but just changed my reservoir about every 4 days, but when I returned to my previous Endo recently, she was emphatic that I change it no more than every 3 days. So, I’ve been complying. I think it’s due to insulin degrading after 3 days.

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Bad insulin mes you up

The reason insulin is stored in glass and why we shouldn’t pre fill cartridges, is that insulin loses its effectiveness when exposed to plastic. After 3 days there is no appreciable loss, but after that it here is a measurable decrease in its effectiveness. I’ve never tried to leave insulin in my pump for more than 3 days or maybe 4 on the outside so I have no experience with it, but I think it’s a good idea to change it out more often anyway

Doing much better now. I finally got my sensor to be accurate. I increased my carb ratio for supper and I make sure I prebolus about 10-15 minutes before eating. I think that being more relaxed has helped. Today I got 99% on target.


Emotions definitely impact my levels. A couple of years ago I was vacationing in The Keys……relaxed on the beach, hanging out with friends, listening to music, no stress……my BG levels were awesome! Ate and drank….didn’t matter. Numbers stayed in great range. At times I thought my CGM was broken! Lol. As soon as I got back home……crazy numbers again.


Maybe, but probably not.

Every vial of Humalog in the USA comes with paper instructions, FDA approved. In section 16.2 it says change Humalog in a pump at least 7 days. To have this number in the instructions, the FDA must have seen and accepted evidence that this is safe and effective. And like expiration dates on medicines, it doesn’t mean it goes bad on the expiration date, just that they’re saying it should be good through that date.

I understand that I probably just outraged everyone who posted above that the insulin reservoir needs to be changed every 3 or 4 days. No offense intended.

Well my experience supports to leave an infusion site in for five days max. I become less responsive to insulin. Whether the degradation of insulin within the plastic pump reservoir contributes to that is not known to me.

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I try to change my infusion set every 3 days, but have had that slip a bit every once in a while. And, sometimes have noticed a problem then, though not usually. It’s been more likely, with me, for the problem to be that the site gets uncomfortable after 3 days, but sometimes it also doesn’t seem to be working as well, and in those cases I usually notice an irritated red spot when I remove it, not a good thing.

But, except in hot weather, I routinely fill the cartridge for at least a normal 6 days, which occasionally has lasted up to 9 days, and have only ever had any problem with insulin losing effectiveness from this in the hot weather. So I seldom am changing set and cartridge at the same time. I’m using Novolog.

I don’t believe this was necessarily due to insulin poitency unkes ut was denatured before use. by overheating or freezing. It would be more likely if the colonoscopy were in the summer. While insulin does lose some potency due to being in plastic, it’s not as much of a problems with more modern systems if the users are wearing CGMs and making needed corrtions each day, as it was with BGMs and checks 3-5 daily.

I had a similar experience after my most recent colonoscopy. And looking back at my logs when I was on MDI using refrigerated insulin, I had higher than normal blood sugars after my previous two colonoscopies for several weeks, one in the spring, the other in the late fall.

This last time it took me a month to get back to my normal. Fortunately, having a CGM plus Control-IQ I was able to make the corrections each day to keep my BG and time in range under control. It just took a lot more attention after dinner.

Two things happen as result of a colonoscopy. The first is that you gut is completely empty. You were on a clerar liquid diet with no fiber or fat. That allows food afterward to pass through your intestine much faster than previously. The immediate effect of that is your poplation of internal intestinal biota is completely disrupted.

Thoise bacteria do more than digest food, but that immediately changes the way you metabolize the food that you eat. The net effect is that your digestion is dirupted enough that enough your insulin to carb ratio(s) are inaccurate. You are also open to internal “infections” -coups and imbalances of bacteria that aren’t optimal for your nirmal diet.

This is what happens in any ecosystem when a drought or other condition causes an interuotion of food sources. Some species survive better, others reproduce faster. In humans oneof the functions of tye appendix is to preserve a sample of all those bacteria during a famine. Not having one will cause a bigger disruption after a intestinal cleanse.

The fastest way to recover may take weeks. Mine is to eat a wide range of foods that contain different beneficial bateria and nutrients along with my normal diet. I do this with yogurts and cheeses, samll amounts of “uncured” sausages and other foods that can be earen without cooking, plus adding soluble fibre to each meal.


I doubt the insulin went bad. I have had a few colonoscopies with no effect on my blood sugars. One thought might be to open a new bottle of insulin, change your site and insert a new sensor and see if this helps. It’s horrible when you can’t get your blood sugars back in line.

I mostly agree with Marie20. I’ve been pumping since ~2017 & recently when I’ve managed better BG control, I noticed BGs rising after 4 days, so I’m changing my insulin & cartridge every 4 days!! Much better now!!


@Dee_Meloche You issue probably resolved by now. I had a similar experience with a procedure and it turned out that some of the meds/additives to IV fluids probably caused the issue for me. I talked with the doc, got a list of everything used, and researched the interactions/common reactions for diabetics.

Very interesting. Yes, my issue is resolved now and my sugars are more stable. My colonoscopy was all clear so that’s good news! Just waiting for the 780 software update for the 780.