Sudden drastic insulin delays and reductions

I’ve been on an insulin pumps for over 5 years, type 2 for over 30 years. I use about 140 units of U-100 insulin per day. Generally OK and expected insulin response, although my A1C averages around 8. I wear a Dexcom for CGM. Insulin effective for about 4 hours after a bolus. Infusion site is my stomach, left and right 80% of the way around, changing location every 2.5 days.

Over the last 2 months, I’m suddenly seeing days (every 7-10 days) where I am extremely slow to respond to my insulin, resulting in lunchtime boluses of fast acting Novolog not having an effect until 4 or 5 hours after bolusing, eventually resulting in lows all night long while I’m trying to sleep. When this happens, I know through experimentation to reduce my basal rates to about 20% of regular and to significantly reduce bolus amounts until I see my BG begin to rise during the night. If I don’t reduce my bolus rates, I experience prolonged lows for hour after hour during the night even with taking glucose every 30 minutes.

For example, it happened yesterday afternoon, when my BG went towards 300 mg/dl after lunch but did not respond to my insulin bolus for several hours, after which my BG kept dropping steadily even beyond the 4 hours the bolus should have been in effect. I ate dinner and did not take any bolus because I could see my BG still dropping from the lunch bolus; the food at dinner did not seem to effect or increase the BG. By bed time at midnight my BG was still dropping steadily and was getting close to a low, so I reduced my basal rate to 20% and took some glucose. That steadied my BG until around 4am when it finally began to increase at about 40 points per hour. Now at 6am, after no dinner insulin and running reduced basal rates for several hours, I have used significantly less insulin that I otherwise would have and have to begin dealing with the high BG.

What could be causing the sudden extremely slow response and build up? I’m honestly terrified I’m going to die during the night from low blood sugar and this is significantly impacting my personal and work life.

Just a couple of thoughts here, since I don’t know all the answers on your situation:

Whenever I take a shot of more than seven units of insulin, I take multiple small shots. When you create a large pocket of insulin under the skin, absorption is slowed and the effect may well last longer than the typical 4-5 hours. This from Dr. Bernstein.

My question to you is, what was your BS before the meal when you went toward 300? I always lead my meal with insulin by about a half hour. But, if it’s already high, I may delay the meal even longer AND take more insulin to cover. I find it’s MUCH harder to bring a high number down than to keep it there in the first place. A single high excursion may take me a day to recover from.

Finally, there is Dr. Bernstein’s Law of Small Numbers. When you eat significant carbs and take large insulin dosages, the errors are likely to be large. That puts you on the roller coaster of highs and lows. While not everyone agrees with Dr. Bernstein’s approach of extremely low carbs, I think most agree that at some level of carbs, control is diminished.

Hope that helps. It may be useful for you to describe your approach to food and insulin balance. That may give you more detailed responses. As to the question, "Why did my diabetes respond differently today than it did the day before?: If we knew that, we could write a mega-million dollar best seller and we’d all sleep easier at night!

My pump regiment has been mostly the same for the last few years, with very few changes.I take 20-25u at each meal, with lunch and dinner my primary meals and some occasional snacks. Each meal would raise my BG around 100 points before coming back down. This worked pretty well thru those years, but I did tend to under count my carbs because of how much insulin I used. If I had to take more than 25u, then I would set the later portion of it on a 30 minute square wave bolus to give the first dose time to absorb a bit and to avoid inflamation and leakage around my Mio infusion set. I seldom had lows and while my BG did climb after each meal, I could usually bring it back down within 4-5 hours. Most importantly, when I took insulin I would see my BG rise began to slow down and reduce within an hour to 90 minutes. I could see cause and effect: take insulin, and see it effect my BG. While my control wasn’t perfect, it did work.

Then 2 1/2 months ago my doctor suggested switching from Novolog U-100 to Humulin R U-500 to reduce cost and make each pump refill last longer so I could be less conservative about counting carbs. We did that switch (adjusting all pump settings by a factor of 5) and it started out ok. I decided I also wanted to lose weight so I started eating less in general at the same time. At 6’2" I was 290 lbs with most of the fat in my stomach.

When I ate in the afternoon my BG would rise much higher than expected, and at night I would have unexpected lows. So I raised my lunch bolus and basal rates, and lowered my early morning rates. … And my afternoon BG went even higher and my night BG went even lower. Repeat this a few times. In retrospect, it was like the “rapid acting” Humulin insulin was working for more like 12-14 hours with a very long start delay.

But then we had to evacuate due to a hurricane, and with the stress and worry of that I was eating a lot less. And having these dangerous lows while in a hotel during an evacuation, with unknown access to medical and sugar sources caused a lot of stress. Once we were finally back home, I experienced an extended 6 hour period of BG lows (all night, no sleep) even while consuming glucose gel, followed by 6 hours with the pump actually removed while still maintaining a constant BG around 130 (???), and I decided to switch back to my old Novolog U-100 insulin and restore my prior pump settings. The Doctor agreed, given the strange U-500 behavior.

Things went well for several weeks on the restored U-100 regiment, but now I am having the delayed insulin response again, but with the Novolog insulin this time. Meanwhile, I’ve lost about 30 pounds in the last 2 1/2 months.

At this point I’m terrified of eating anything, and get nauseous around lunch and dinner because of the worry about having the delayed insulin reaction for whatever I eat. But I also know that not eating will just screw up my metabolism more.

So my question is not “Why did my diabetes respond differently today than it did the day before?” but “Why does rapid acting insulin sometimes act like intermediate/long acting insulin, while my basal needs drop drastically, only to go back to normal a day later?” This isn’t a small change in delivery, but a massive reduction with no serious changes in exercise or food intake. Having to stay awake an hour or more during the night to suspend my pump, take glucose, monitor my BG, and then set a 20% temp basal until morning is also messing with me and causing highs once I do wake up, but I need to stop the insulin for a while when I get a low or else it just keeps dropping.

I don’t see the cause and effect when this conditions occurs: taking rapid acting insulin does not cause BG to lower until hours later, and taking glucose gel is slow to recover. Then the next day it may be back to normal.