Never had insulin not work

Scratching my head here…been T1 for 42 years, and for the first time, my insulin doesn’t seem to be working. It’s a new vial, expiration date 4/2021. It’s from the same lot/box as the vial I just finished, which had no problems. For the last several years I’ve been on MDI, so it has nothing to do with a faulty infusion set since there’s no pump in the picture. I’ve used about 30% more Novolog today than I usually do, and I still can’t get my bs under 200.
1 unit usually brings my bs down about 80 points, so I’m pretty sensitive to insulin. I don’t have a cold or the flu, so I just can’t quite figure out what’s up. Any ideas?

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You could have a hidden infection, like a tooth infection. But insulin can be bad. If something like that happens I would try a new vial to see if you get different results. You never know what could have happened. Maybe that one bottle in the box was sitting next to something hot type thing. I have had a couple of pens been bad before.

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Other possible factors: change in other medication—e.g., a cortisone shot will have this effect and it can last for days or even weeks.

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There could be several causes and a few have been noted. It seems unlikely that it could be poor absorption since you were on MIDI just a few years ago but when I have this problem I immediately change the site and readings start coming down. If you do not change your sites enough you could start having absorption problems and for me that hinders insulin from dropping BG not entirely but significantly.

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Depending on your age, it could be a hormonal change. I’m peri-menopausal and coming up to the end (fingers crossed!), and I’ve noticed some fluctuations like this.

Edited to add: Have you checked with multiple meters?

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My thoughts immediately went to insulin sensitivity when I read your post. While I know that we can be generally insulin sensitive or resistant, our sensitivity varies throughout the day and can episodically spike, too, like when we experience an infection.

Woman routinely report here that their insulin needs go up and down related to their monthly cycle. Like many people, I am more resistant to insulin in the morning than I am in the late afternoon.

Poor sleep has been shown to increase insulin needs the following day. Any infection, as mentioned upthread, can drive insulin needs up. Even infections you can’t feel can raise insulin resistance. I’ve heard about dental infections in teeth that have had their sensory roots already removed and may not be felt.

You could try another vial from a different lot/box to see if you have any different results.

I’ve found insulin to be very reliable except when I froze it. It’s possible that your insulin is bad but not likely.

Good luck with your detective work!

Edited to add: I went through a period where I had slowly gained weight over many years and I finally reached a point where insulin corrections did virtually nothing to bring down a high blood sugar. I had become very insulin resistant, much like a classic T2D. I am T1D but became insulin resistant. Once I limited carbs in my diet and lost weight, those symptoms went away.


+1 for trying a different vial!

I’d also suggest, before you try a different vial, try a different site for your injection, one that you’ve never/rarely use. After 42 years this might be impossible, but if you can, try.

Another consideration, has your activity level decreased any?


Are you positive that you took your long lasting insulin?


Do you have another vial. Might be that bottle only is bad.

While extremely unusual, a bad vial in the same lot can happen. In the last 46 years, it has happened to me 3 times. The last time for me was in 2016, when I was forced by my PBM to switch to Novolog from Humalog.

My very first vial was bad, which of course really had me going bonkers because it was truly the same effect as injecting saline.

Fortunately, I still had some Humalog left, so I swapped out my cartridge and got my BG back into range. Later, I injected from the bad vial to bolus for a meal. After it had zero effect, I injected from a second vial of Novolog (same lot#) and it had the desired effect.

I would also try using a site that you haven’t used before to make sure you don’t have an absorption issue.

Wishing you success and sad to hear you’re having this problem.

I am having a similar problem. I have had T1 for 30+ years with MDI (waiting on a pump). 2 months ago Humalog started taking 1-2 hours to start working, and then my BG drops like a rock. I switched to FIASP which worked great (fast) until 3 days ago, when it just seemed to work but was ‘weaker’ (needed to double my injection). Last night and today it does nothing at all and I am back on (slow) Humalog. I have tried multiple sites for injection, also tried a new box of FIASP pens, to no effect. I hate being on Humalog again (have tried APIDRA, did not work well). Not sure what to do other than visit my MD again.

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Welcome to TuDiabetes @Barry2.

There have been a pretty significant number of folks who have reported great results with FIASP only to have poor results after a period of use. Some have reported that because FIASP is basically novolog with niacin, the speeding up effect of the niacin seems to “wear off” over time. I might also note that many of the users that have reported issues are pump users, so perhaps MDI users aren’t effected the same way?

Thanks to everyone who replied with their ideas and suggestions. This forum is so helpful! Thankfully, my sugar levels are better today, but I’m guessing it has to do with issues of absorption and maybe needing to rotate my sites more. I hadn’t even thought about that. It’s also useful to know for the future that sometimes a bad vial can be in the same lot as a vial that’s ok. This is the kind of stuff that fellow diabetics know, and doctors often don’t.


Thanks YogaO

My problem is not that it has become slower, it is more like injecting water - it does absolutely nothing. Last night my BG was going high so I took some FIASP and waited over 2 hours but m BG just kept going up. I finally took some Humalog, which worked after about an hour. I have given up in FIASP for now, but I will try it again after a few days to see if that helps - I really like the fast action (when it works).


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I’ve seen a couple of reports with the same sort of problem. I tried it and initially thought it was great, but then it started working about the same as Novolog, plus it was more expensive, so …

I hate hearing this. I absolutely love FIASP, but have only been injecting it for a few weeks.

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A classic case of YDMV?

Hoping it continues to work well for you, Marilyn.

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You may be experiencing anti-insulin antibodies. Any way you could try a different formulation such as Humalog or FiASP?


Stress is a huge factor. Over the years I’ve discovered stress can be much more intense than I realized at the time. Numerous times my high BG would go away after some event passed that I did not realize was apparently giving me much more anxiety than I sensed it was.

Fighting illness while not actually feeling sick yet (and sometimes never actually getting sick) has also been a cause of extended high BG for me.


FWIW I’ve been using it for over a year, and for me it continues to work much better than Novo/Humalog. I can pre-bolus and see my BG starting to drop within 15-20 minutes, whereas with Novolog i was sometimes still waiting at 45. It can actually be a little too fast with high-fat meals. I had an episode with pizza (inevitably) where it kicked in too soon before the fat-delayed carbs and gave me one of the scarier lows I’ve had in recent years. Any “fade” I’ve experienced seems possibly just due to the novelty wearing off. And though the charts suggest otherwise it also clears much more rapidly, making it distinctly more effective to set temp boluses to avoid exercise lows, one of my bugaboos.