Worryingly Fast Insulin Absorption

Just wondering if anyone else has experienced this - sometimes, when I inject insulin, the whole dose seems to act immediately. This has happened 4 times in the last year, 3 of which have been in the last 3 months.

The first time it happened was with a 3 unit dose of Levemir (injected into the leg); the last three times were with 3/4 unit doses of Novorapid (injected abdominally). I use the Dexcom G5, so on these 4 occasions, I have seen my sugars plummet quite scarily as if dropping off a cliff edge, and the fall-rate alarm has sounded - about 10 points over a 10-15 minute period. There's no error with the Dexcom, as I've confirmed the situation with multiple finger-pricks.

It's as if the insulin is being injected intravenously - but that seems so unlikely according to my consultant. Could it just be that I'm not rotating sites enough? - I know that can cause absorption issues, but this seems ridiculous. It's extremely frustrating, as ever since I had a really bad hypo in June 2016, this is exactly what I've been worried about, but constantly reassured would never happen. Have spoken to my consultant, but it just seems to be one of those unexplained diabetes-related things.

By complete chance, on each occasion, my sugars have been too high to start with, so luckily there's been time to react by taking lots of glucose gel; but it's quite worrying, as if my sugars were around 5.0 to 7.0 to begin with like they should be, such a drop would be horrific, and any glucose I took surely wouldn't be able to act quickly enough. Any thoughts would be most welcome! x

Hi Helen,

Thanks for the reply, and the kind words. I don't think either of those things apply unfortunately. I'm really careful not to inject into muscle; I use 5mm needles, and grab sufficient fat; also, whilst I do exercise, none of the 4 occasions were proximate to exercise (the last occasion was this morning, whilst I was still in bed having just woken up!). Also, I don't think previous doses are responsible, as I usually leave it around 4 hours before I inject again; and the sharp drop always coincides immediately with an injection of insulin (i.e. it never happens other than straight after an injection). I think it's probably true I don't rotate my sites enough, and I have some small bruising abdominally - that's all I can think of. I stick to a low carb diet, so hopefully that would mitigate the extent of any sharp drop.

alphabeta said:

Can you try 3.5 or 4 mm needles? And please rotate your injection sites next time!

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Good idea thanks - I think I'll get 4mm ones at my next prescription - has to be worth a try. I inject abdominally mainly for meals - as the first time this happened, it was after a leg injection - but it's now happened more frequently with abdomninal injections so I suppose I should try the legs again.

kitedoc said:

Maybe, just maybe you hit blood vessels on those occasions ? Most of us do not drawback on the syringe plunger before injecting and so may not always be aware of hitting a blood vessel. Yes, on 3 occasions in 51 years on insulin I have noted blood in the syringe but can i have been that lucky to have really only had that few 'hits'?
I have noted more than that number of unexplained sudden hypos though !
The problem I found with not rotating injection sites was irregular but not super-fast absorption type issues, (I think) !!
I hope things sort out !!

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Thanks @kitedoc - I agree, not rotating sites leads to irregular absorption - but surely not all at once! I may have hit a blood vessel, but as I use insulin pens rather than syringes, so there's no opportunity to drawback - however, it's quite rare to inject the whole dose into a blood vessel; I've been reassured it's not possible, though I can't think of any other reason!

JMK1954 said:

I have found that the recent hot weather has caused my BS to plummet frighteningly fast. It might be worth taking the temperature into account.

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Hi @JMK1954 - it's possible I suppose; how fast are you talking? The first time this happened was in cooler weather, but perhaps the heat is doing something.

JMK1954 said:

I've had to reduce my basal by 20% to deal with massive hypos since the hot weather arrived. The word I have seen used is that in hot weather insulin 'potentiates' faster. I ran this past my GP and he confirmed the meaning was that it worked faster and more effectively. For me, that was putting it mildly.
I only hit the problem last summer after 52 years of type 1. I was ignored by the DSN when I said I believed it was something to do with the heat. I know that part of my problem was that a hypo was followed by a spike, so the BS result before the next meal still showed the results of that spike. However, when I had my insulin for the next meal, the spike disappeared very rapidly, so the rate of the fall was exaggerated. I have always understood that this is quite usual with a spike caused by a hypo. Is this worth consideration ? I hesitate to give a rate of fall because this is partly dependent on the type of insulin, so may be misleading. Personally, I would find this more likely than repeatedly hitting blood vessels.

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Very interesting @JMK1954 - I'm sure there's a lot we don't know about insulin absorption, but your explanation sounds plausible; as I mentioned earlier, I thought it was just a lucky coincidence that on each of the 4 occasions this has happened, my sugars have been high to start with - however, given what you say, it may not be a coincidence at all; perhaps there is some underlying and unexplained mechanism the body uses to vary insulin absorption in certain circumstances. My concern was that I'd experience the same drop when sugars are in the normal range to start with. The body certainly works in mysterious ways.

Robinredbreast said:

Hi, not sure if this is helpful or relevant, but I had plummeting BS, 6 years ago, in 7 minutes, very worrying at the time, I worked in a pharmacy and the 7 minutes was walking back after lunch at home. Anyway, what I found out months later was I had Coeliac disease and I wasn't absorbing the nutrients, so basically I was having my Insulin on an empty stomach.

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Hi @Robinredbreast - thanks for the reply, and sorry to hear of your experience, that must have been very worrying. I had considered whether there might be food absorption issues (as sometimes any glucose I take to raise my sugars seems to take a long time to act). I actually had a Coeliac test last month, which was negative. I don't think it's food absorption related in my case though - as on the occasions this has happened, the drop has taken place in the immediate 15 minutes or so after the injection; and I wouldn't normally eat within that first 15 minutes in any case. I'm glad you found an explanation in your case!

tim2000s said:

The big difference in hot weather is that to lose heat your capillaries dilate to try and reduce your temperature. This has the side effect of them having more surface area though which insulin can be absorbed and carried away in the blood, which leads to faster absorption. I'm not sure that that would lead to the speed of absorption you've been concerned by @Odin004 but if offers another potential explanation (although not for Levemir).

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Thanks @tim2000s, that's interesting - I agree it seems unlikely that the heat would cause this kind of incredibly fast absorption; however, if I've not been rotating my sites enough, I wonder if there's some curious interplay between any issues this has caused, and the heat.

@tim2000s @helensaramay @kitedoc @JMK1954 @Robinredbreast I was doing some research and also found that lipohypertrophy can cause "unexplained" hypoglycaemia - this link says that "In the Spanish study of those with LH, 39.1 per cent had unexplained hypoglycaemia and 49.1 per cent had glycemic variability" - https://diabetestimes.co.uk/insulin-injection-users-at-risk-of-lipohypertrophy. There are also a few other references to the same thing around the net.

I don't actually have anything resembling lipohypertrophy that I can see - but perhaps this suggests that (as expected) I'm not rotating sites enough.