LANTUS & LEVEMIR - What is the Insulin Depot?

You may have heard reference to the Lantus or Levemir Insulin Depot. What does that mean?

Lantus and Levemir both fall into the category of “depot drugs.” Pharmacologically, the two insulins work in different ways, but both have the characteristic of being absorbed slowly by the body. The result is an extended action. These insulins tend to display a cumulative effect, meaning that what happens in one cycle can affect the next cycle, or even the next several days. This is part of what allows Lantus and Levemir to create those beautiful, flat curves, so it is worthwhile to spend the time to understand the depot.

Here is a great reference that explains the Lantus and Levemir depots in layman’s terms:

Lantus and Levemir: What’s the Difference

Glargine (Lantus):

Detemir (Levemir):

Have you ever wondered why, when you are giving the same amount of insulin every time, the response is different in each cycle? Sometimes the numbers go up for the whole cycle, sometimes they go down, sometimes they stay flat, and sometimes they actually “curve.” The answer often lies in the depot. Did you skip a shot or give a partial shot at some time in the past few days? That can result in higher numbers for several days as the depot replenishes some of its lost stores. Did you increase the dose? This can result in a change in the size of the depot and can lead to a temporary adjustment in the amount of insulin available for use. Did you decrease the dose recently? A dose reduction will usually result in a need for less stored insulin. The excess may be released into the bloodstream faster than usual, especially if several dose reductions are done back-to-back.

Another interesting note from the Boulder Medical Center:

So sometimes, the answer is “just because.”

How long does it take to fill or empty the depot?

Again, from Boulder Medical Center:

Practical experience on FDMB shows that as a generalization, the depot can affect up to 6 cycles. The time tends to be less when a cat is on a smaller dose, and more when a cat is on a larger dose. Other factors can apply as well, but using the generalization of 6 cycles is a good starting point until you have learned your particular cat's patterns.

Now you are probably asking "How on earth can I use this information to understand my cat?".

Try to look at your spreadsheet not in 12-hour cycles, but in “waves” of action over a period of several days. Look for overall trends more than individual numbers. If something jumps out and doesn’t seem to make sense, go back 2-3 days and think about any changes that might have occurred in insulin, timing, exercise, health, food, etc. If the big picture is making sense but you see one cycle that doesn’t fit, then keep that 20-50% variation in mind and just wait it out.

More reading about the glargine and detemir depots:

Internet Journal of Endocrinology: Insulin Detemir and its Unique Mechanism of Action
Textbook of Diabetes Mellitus by B. B. Tripathy
The Mechanism of Protraction of Insulin Detemir

Additional note:
The Insulin Depot is not to be confused with Carryover (insulin effects lasting past the insulin’s official duration) and Overlap (the period of time when one insulin shot is diminishing and the next is taking effect).