Bouncing is rebounding Hyperglycemia. Its normal for a cat to experience a rebound or bounce when starting on Lantus and experiencing lower numbers they're not used to. Dude is used to high numbers is the 500's +, so when the dose takes him down to the 400s or less, the liver panics because it is not used to seeing numbers that low, even tho technically they are high numbers, but the liver just recognizes it as, "her we haven't been consistently this low before". When the liver panics, it compensates for what the liver thinks is a low BG and shoots out stored blood sugar.
Bouncing is normal and at the same time annoying, but we just have to be patient and wait it out for the 4 to 6 cycles. Only then can we truly see what the new dose can do. For example, my cat was bouncing when his normal bg values were in the low mid's (140s) to lower 100's (120/130) and he started seeing 60s and 70s for the 1st, 2nd, and 3rd time, he would then bounce to the 170/180s. Its frustrating to see, but its its normal, and part of the process. We just have to be patient and wait the bounce out.
The depot is like a spare tank or reserve of insulin. When we give insulin most of it goes straight to the blood and some gets stored under the skin as a spare tank. When you increase a dose you have to wait 4 to 6 cycles to see the true potential of the increased dose because not all of the dose is getting to the blood some is being put towards building up or filling up the spare tank to match the increase in dose size for that doses bigger size spare tank.
When you decrease a dose the spare tank/depot/reserve has to adjust to the small dose size, that means some of that spare tank has to spill out into the blood to match the spare tank size for the smaller dose. Again, this can take 4 to 6 cycles and you won't see the true potential of that newly reduced dose till the spare tank adjusts to the size of the smaller dose size.
If it helps, feel free to take a look at Mazis SS and if you scroll all the way to the right, I have a list of notes on describing dose changes and bounces and what to expect.
The main message is just try to be patient, I've made the mistake too of jumping the gun and increasing mazis dose because I wasn't seeing the numbers I was expecting to see. The only way to identify true bouncing is by picking it up on testing and being patient to let the bounce ride out. Since Dude is new to Lantus, I can assume 99.9% we are correct in guessing that Dude is experiencing bounces.
The reason you were seeing increased numbers when dude wasn't eating could very well be because the Liver was compensating and was releasing stored glucose. If the body recognizes it is in starvation mode it will release stored glucose.
The body is good at compensating for changes. For example, if blood pressure or volume drops the heart rate increases to help get blood to vital organs, while forgetting about the non important organs. If the liver recognizes the body is in starvation mode or recognizes levels of glucose that is lower than what it is used to (even if those numbers are considered high)it will think its low on glucose and will release stored sugar.
I hope this helps and wish the best for you and kitty!