I didn't get an IM vet right away, not until Neko got a bit more complicated. A cardio vet is best for checking out the heart. You don't really need to have his brain checked, imaging is not necessary unless you are proceeding with treatment such as hypophysectomy or SRT (radiation). Since George is 17.5, I might not consider hypophysectomy due to the risks. Both it and SRT require anaesthesia, at least a couple days worth, so getting his heart checked (echocardiogram) would be a good first step. Hypophysectomy is only available in North America at Washington State U and AMC in New York as far as I know. So you have travel plus it's pretty expensive. Many people have good results with cabergoline, but I've also read it depends on size of the tumour. It's a relatively cheap option to try first, and can help alleviate many acro symptoms, include reducing the insulin dose needed.
Not sure who said to bump up the dose by 1 unit, I would suggest 0.5 units increase at this point. That's also what TR suggests.
This is a two pronged answer. First, the tumour doesn't change that quickly on it's own. It's not like you need 10 units 1 day and 5 the next. I went through SRT twice with Neko and we've had several other people on Lantus or Levemir do SRT or cabergoline safely by following TR for dosing and guidance from here. Hypophysectomy is a different thing as it removes the pituitary, and changes can be immediate. I'd follow whatever the surgeon doing that work suggests. I've seen cats both on longer lasting and on Prozinc have hypophysectomy.
The second part to this answer is which depot insulin to use. Lantus has an acid base, and at some point you could find that George notices a sting at the higher doses. If that happens, people usually switch to Levemir which is not acid base. It has similar action, though on average later onsets and nadirs by a couple hours.
