Hi, and welcome to the board!
I would test as often as you can to ensure that he/she's not dropping too quickly, and be sure to mark it in a book so that you can transfer the #s to the spread sheet. I would highly recommend getting a spread sheet set up so that you can post your kitty's #s on it. Be sure to put it in your signature so that the experts can quickly click on it and see how he/she's doing. Here's a link on how to create one for him/her:
http://felinediabetes.com/FDMB/viewtopic.php?f=6&t=18207&start=0
Here's the main link where the above came from, but it also has a whole lot of information on it to look over, including how to do curves, etc.
http://www.felinediabetes.com/FDMB/viewtopic.php?f=9&t=18139
Here's the Tight Regulation Protocol that is followed. This helps us to control/manage our kitty's diabetes:
http://www.felinediabetes.com/FDMB/viewtopic.php?f=9&t=1581
Most of us increase doses by 0.25u, and in some cases by 0.50u, but that's not too often. Your old vet suggested 4 units of Lantus to begin with, and frankly I think that's a bit too high in the beginning. Most, if not all, of the people on here start dosing with 1u BID (2x a day), and then increase by 0.25u after 3-5 days (6-10 cycles... A cycle being a 12 hour period). Lantus is a 12 hour insulin, and needs to be administered every 12 hours (but then, you probably already know that).
A low carb diet is the key with helping to reduce the blood glucose #s. Some cats do well on a higher carb diet than others, but it all depends on the individual kitty. My cat, Blackie, can't have a high or medium carb diet as it'll spike her #s through the roof. Even a crumb of contraband (the kibble that the others eat) will spike her. So, she's on Evo 95% Chicken & Turkey 8x a day as mini meals. You may need to divide the 2 meals that you're feeding into several smaller ones throughout the day. This will help to stabilize the #s better, and also help to keep your kitty fuller longer. Eventually, he/she will begin to show less signs of being so hungry, but it'll take time.
Make sure that he/she has plenty of fresh water available, and you can always add a few teaspoons of water to your kitty's food. This will help to keep ketone levels in check, and possibly avoid them. If your kitty is in the high range of #s, be sure to get a ketone check by placing a ketone strip in the stream of urine as your kitty urinates (or get some fresh, cleaned aquarium gravel, place it in the bottom of the litter box, and collect the urine that way... Make sure that the regular kitty litter is out of the box before you do this).
I have no experience with acromegaly, so hopefully an expert can come by and help you with that. Good luck, and welcome!
