hi - i'm sure we can help you, but it's often like untangling spaghetti to figure out what's going on. so be patient and we'll give you a hand. usually people answer here pretty quickly, so check back often.
lantus is a depot-type of insulin, meaning that it builds up in the body and releases over time. you can't use it to knock down numbers, it just doesn't work that way. did you only give him one dose of the 10units, or more than that? you need to monitor him for the hours after you gave that shot - i'd test every hour and if it looks like he's going down too far or too quickly, either post on here or get him to the vet. if you went from 7u to 10 units, you increased his dose by nearly 50%. that's a lot.
if you can do the spreadsheet that serryn gave you, that is the best possible way for us to see clearly what's going on.
there are things that can cause unremitting high numbers - it's possible you've got a high dose condition. there are 3 - acromegaly, insulin antibody antigens (iaa), and cushings. there are also other things that are not high dose conditions that can make it hard to get a cat regulated - too many carbs, infections including dental inflammation, steroids use (any asthma?).
cushings is characterized by fragile skin that tears easily - they are usually females.
the characteristics of acromegaly include a need for more insulin than average, the cats are often male (but i know of 3 females), some signs that they may or may not have include large overall, extra large feet, tongue, forehead pushed forward (more vertical from eyes up than before), an enlarged muzzle, spreading upper teeth, mega-colon, stridor (sound of rattling when breathing from excess tissue), and punkin's voice changed. he was diagnosed with acro last june 1st.
iaa is when the body builds up antibodies against insulin. so as the dose goes up, the numbers might go down a little and then they go up even farther. more insulin and higher numbers.
we have cats on here with both acro and iaa. those are more common than cushings, although we've had cushings cats here.
the tests for those 2 are relatively easy - a blood sample sent to Michigan State University can diagnose them. here's some basic info on all of the conditions and the tests.
http://www.felinediabetes.com/FDMB/viewtopic.php?f=12&t=375 if you're in the US, the cost of fed-ex for the blood sample is $85.
I had punkin treated for acromegaly at Colorado State University last September.
it's too early to comment on whether or not he's getting an appropriate dose without more information.
our general process is to have the cat go on an all-canned food, all low-carb diet and increase insulin doses by small increments - i am NOT saying you should make any sudden changes right now. without knowing more it's hard to know if Flop's insulin increases were done in a way that says he really needs that much insulin. he might. if he's eating dry food, has an infection, is getting steroids, etc., and his doses were raised by too big of increments or too quickly, he could be overdosed. no way to know without having more data.
are you able to get the ss up and some info on it, as best as you can provide it?