@julie & punkin (ga) wrote this explanation of how Lantus and the depot work. It REALLY helped me to understand why dose adjustments are not made based on the pre shot numbers but on the nadir and how the depot grows and shrinks affecting cycled. I hope it helps you, she said it was ok to repost it.
julie & punkin (ga) said:
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With depot insulins like Lantus and Levemir, your dosing decisions are made by answering the question "how low does this dose make my cat's blood sugar go?" It's really hard to suggest what to do with the dose because nearly every shot has a different dose. Try just holding this and see if you don't have more stable numbers.
The depot is important to understand - I wrote this below for another new member. See if it helps you understand a little more about it.
With a
depot insulin, when you shoot, some of that insulin goes to work right away and some of it builds up in the body. Then what's in the body releases over time. Sort of like a timed release medicine. The depot size is in relation to the size of the dose. So a 3.0u dose has a bigger depot than a 2.0u dose. There's a great description of how Lantus works in the link above, specifically the one called "Lantus and Lev: what's the difference?"
Increasing the dose means that the depot must "grow" to fit the size of the new larger dose. that's one of the reasons that when you increase a dose, you also hold the dose for at least a few cycles, usually 6 or more. You want to see what the dose can do when the depot is at its new, larger size and is giving out at that rate.
Decreasing the dose means that the depot has to "shrink" to fit the size of the new smaller dose. If you had low numbers this cycle and reduced the dose of the next shot, then had low numbers again in the morning, we'd probably "blame" the low numbers on the depot action from the previously larger dose. The depot can take as many as 6 cycles to decrease to get into equilibrium again with the new smaller dose. If the low numbers occur after 5 cycles, then we might think you should take the dose reduction again. If it's in the first couple of cycles after a dose reduction, that's more likely to be from the previous depot.
With a newly diagnosed cat sometimes they can come down the dosing scale really fast, so sometimes a cat does need to take the reduction, even if it's soon after the last reduction. Everything depends on the context.
Another way we sometimes describe it is that with a depot insulin, you are steering a barge. Once it gets going, it will continue on its path. In order to change the path, you've gotta do something drastic! The older insulins were more like steering a speed boat - you look at the preshot number, decide on the dose based upon a sliding scale, shoot in and in 8-10 hours the insulin is out of the cat's system. So you're basically starting from scratch with each shot.
Hope some of that helps[/QUOTE]