Insulin Action Time - Rapid Changes

Did any of you experience rapid changes in insulin action time (daily/weekly)? e.g. one day humalog acting for 2,5h & the other for 5h given the same amount of activity / food?

Do you have any ideas what may be the underlying physiological reasons?


hi @Matt1 , welcome to Type One Nation.

are you on a pump? When I was on Injections, I find big differences in the location I inject. for example, If I am injecting near leg muscle, if I was more or less walking after the shot changed both the absorption and the action. While pumping, I get fairly repeatable timing for onset and action, but again the biggest variables seem to be level of activity or even general circulation such as if it is hot or cold outside.

@Matt1 Hi Matt, and welcome to the TypeOneNation Forum!

Like you, I’ve noticed differences in effectiveness of insulin and “speed” at which insulin will begin its action depending on where [which part of my body] I inject or infuse. My experience has been very much as @Joe wrote.

I will take exception to hour assumption on insulin/Humalog duration - “… one day humalog acting for 2,5h & the other for 5h …”, and this is so that you will be aware of possible “insulin-stacking”. I agree that Humalog can peak well within 2.5 hours if injected/infused into a stressed or soon to become very active body area such as a leg if you are running or brisk walking, but some of it can still be present 4, or 5 hours later. For many decades I’ve been a walker and biker so I haven’t used my legs for injection since sometime in the 1960s; now, just my arms occasionally and now primarily my abdomen.

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@joe I am using an insulin pen and inject (4mm needle) in my stomach.

No two situations are exactly the same in diabetes. But in extremely similar situations (in terms of activity, no stacking, injection site, glicemia, time of day & nutrition) sometimes humalog just magically & r a d i c a l l y extends its action time and action power on my system.

It is typical that sometimes it does not work as fast and strong as we hope (hormones, stress, inflamation, etc), but what about the opposite situation when you do everything like you always do and suddenly it unexpectedly hits you superhard? on the next shot - things go back to normal…
I started to wonder if anyone else had such issues.

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@Matt1 I see easily 20-50 percent differences in injection site locations and stress or activity can make my sensitivity to insulin go from my average (1 unit drops my blood sugar 32 mg/dl) to between 5 and 200. So I am not sure what qualifies as radical but I’d say those are wide outcomes. I have similar outcomes with i:c ratios. Exercise can give me a 200x difference. I manually (because I pump) select the amount of insulin unless I know for sure I’m having an average day.

I can understand, and relate to, much of what you are experiencing Matt @Matt1 , but I’ve come to the conclusion that the problem isn’t [except for very rare “spoiled” instances] the insulin, but rather my body. Your insulin, Humalog, is manufactured at a very high standard, and a vial [or from vial to vial] should not develop “different strengths” between the hours of 8 AM and 12 Noon. I’ve reached the conclusion, at least for MY BODY, that wide variations in “apparent onset” and “action Duration” of insulin is because of me, and not the product.

Have you considered changing the length of your needle? I expect that you observe the “rotate site” rule, and, at least on my body, the thickness of dermas varies. Just a thought.

Ive done my homework as injection sites/issues were the usual suspect;)
I changed to shorter needles after investigating this topic. skin thickness is about 2mm on ALL humans (and what you need to do is to pierce through the skin), so 4-5mm needle is absolutely sufficient.