Insulin Duration

So how long does your insulin really affect your blood sugar?

It should be pretty easy to test right? In theory all it requires is a fasting bg a bit higher than target, some time, a correction bolus, a bg meter and something to record results on.

Also a good time to check the correction factor – which for some people is different for different times of the day!

I personally have my Insulin Duration figure on my Cozmo pump set to 5:30. That’s five hours and thirty minutes. I want to avoid stacking “tails” (see below), and make sure that all unused insulin is accounted for.

This is a portion of the insert that comes along with each vial of Humalog insulin. It is a graph depicting the blood insulin levels after injection of both Humalog (dashed line) and Regular (solid line).

Insulin Levels

If you look carefully at the graphic, you can see that most of the insulin peaks and then is out of your system at around the three hour mark. But also notice that there is a very gradual and very long tail, reaching almost five hours before levels are back to the starting point.

It is a very gradual curve, but it is there. One could argue that by this time the insulin no longer has any real blood sugar lowering power, which is probably a pretty valid point. But what happens when you have portions of two or three (or more) tails riding on top of each other? That’s right. More insulin than you need.

I first saw this figure (the 5:30 figure) presented in an article by John Walsh, P.A., C.D.E and Ruth Roberts, M.A.

I sometimes would have problems with lows very soon after eating dinner. It made no sense to me at all, especially because I had recently eaten a large meal! Fasting basal rate tests proved that my basal rates were, for the most part, pretty darn good – so I stumbled across this article and wondered if it could be the cause.

Time will tell!

I believe the average figure is about 3:30. What do you all calculate for your insulin duration? I also wonder if your insulin duration changes based on the amount you bolus? Does a large bolus “hang around” longer (or have more affect in the “tail”) than a smaller bolus?

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Scott K. Johnson

Patient voice, speaker, writer, advocate, and Senior Community Manager at Blue Circle Health. Living life with diabetes and telling my story. All opinions expressed are my own and do not necessarily represent my employer’s position. Read more…

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