Well. I don't know if I am the first to ask but here goes:
Have you thought about having Blackie tested for acro or IAA?
I ask because if your dose just keeps rising and you just don't seem to be finding Blackie getting results, there has to be a reason.
I would guess that you could start with the cheaper checking - get full b/w done to ensure all his levels are within range and no problems jump out. Also, when I don't know what's going on, I get the urine checked as well - u/a and ask for C&S-culture and sensitivity - just to be sure that nothing is happening in that dept.
Teeth are another thing that can be a problem and affecting their numbers. I had never taken Shadoe in for dental but when she went for a clean and what was needed, she had 4 iffy teeth with one bad canine pulled and the others were just cleaned up. Her numbers improved and the dose dropped right after that too. If you have the vet do a look-see (you can't tell all that much from visual if there are issues below the gums, but it's a starting spot).
Next is food - what food is Blackie eating as food is a major factor in regulation.
I switched to Lev from Lantus after my two tested positive for acro, and Oliver positive for IAA as well, and Lev was said to be gentler on higher doses.
It could be that Blackie is just a thirsty fella and needs more insulin but I don't know if switching from one to the other will do anything to regulate Blackie. They are pretty similar, so if you can't get him regulated on one, then the other is not going to be any different.
There are differences though:
Lantus and Levemir: What’s the Difference?
About the syringes, I just use the BD ones with the 1/2 unit markings. What you could try to see if it makes a difference for Blackie is to split his shots - give half on the left side of scruff and half on the other side. When you get to higher doses, it seems that some people feel they get better results by this method. If I give Oliver his shot, I split it into left, center, and right with about 2inches between spots.
Talk to your vet about it all, and if you have ruled out all the above, except for the tests, here are the sheets with info where to have the blood draws sent.
IAA Test
IGF-1 (Acro) Test
Cushings is another condition, since you mentioned the coat, but it's pretty rare though possible.
Cushings Info
I can't comment on issues with thyroid, etc, but others here have that knowledge. Others can suggest what you should have your vet test for, and which test result numbers to watch closely.
I do like using Lev, but wish we could get vials in Canada. Why they are not available here, I don't understand, but the 5-pack cartridges are just fine.
It seems like there are lots of ups and downs with Blackie; he is getting some greens, so I don't think you are looking at acro, but it's tough to say as you don't have all that many tests in the evening and lots of cats go low then.
It looks like he's lower at amps but then ends up high at his pmps.
With a couple missed shots, you may need longer to fill the shed so holding the 7u for only 4 shots might have been too fast to see results, and upping to 7.25 made for NDW and more shed to top up. Then, toss in a couple of green amps to cause a few bounces, and Blackie is all over the place.
I wonder what he's doing in the pm that is giving you better numbers for his amps?
I am totally not one to know about dosing info; my method is to fly by the seat of my pants, so my words are just observations.
The others here will be able to see more in Blackie's ss than I can.
If you do switch to Lev I am sure you will be satisfied as most people like it.
