Welcome to Lantus Land!!
Since I don't think anyone has mentioned it, the starred sticky notes at the top of this board contain an overwhelming amount of information to help you understand Lantus, how Lantus works, and will help to familiarize you with this board.
I do have a couple of thoughts about transitioning Jersey to Lantus. As the others have mentioned, no washout period is required.
First, it looks like Jersey has been getting only one shot of Humulin per day. It's not surprising that your seeing less than desirable numbers. It really doesn't matter what insulin you're using, most cats need a twice a day injection given that they have a fast metabolism compared with humans. This is even more the case with Humulin since is is not a long-acting insulin. As a result of the once a day dosing, you see some numbers that are in the normal range, Jersey "bounces" into high numbers and you skip the next shot so the numbers remain elevated, you give the next once-a-day shot and the process repeats. And all of this is on a 0.25u dose of Humulin.
By way of comparison, Lantus is a long-acting insulin. In other words, in cats, it lasts at least 12-hours. Humulin lasts 5 - 8 hours. Humulin onset is quite rapid and it can quickly drive numbers down. Lantus onset is roughly two hours after you shoot and is more gentle in it's action. The nadir -- or lowest point in the cycle -- is at about halfway into the duration of each respective insulin although the nadir can vary. The reason that I bring this up is that given that Humulin is an immediate duration insulin, it's not surprising that you're not getting the results you want with once a day dosing. All of this factors in to how you approach using Lantus based on what you're seeing with Humulin.
I echo Sandy's question above. That's a really good start to the day given that Jersey hasn't had any insulin in 36+ hours. Have you changed Jersey's diet?
Unless these lovely, normal range numbers persist, I would suggest that when you make the switch, you ease Jersey into Lantus and reduce his dose to 0.125u twice a day. In other words, give half of what you are currently giving at each shot time. This also means that the total amount of insulin Jersey is getting will be the same. The dose would look like this:
If your vet isn't terribly familiar with Lantus, you may want to share this journal article with him. This is the article that was published describing the research supporting the use of the Tight Regulation Protocol for Lantus and Levemir.
The article indicates that Lantus is dosed twice a day and it also will provide the guidelines for when doses are increased and reduced. The slightly modified version that we use is in the
Tight Regulation Protocol sticky. The sticky note is also written in plain language making it much easier to read.
Please let us know if you have questions. The people here are very generous with their time and information. We're here to help!
