As far as I am aware he has not had DKA or Ketones and he has never been on steroids.
If your Stanley ever had DKA (diabetic ketoacidosis) you would know.
Ketones are less likely for you to be sure of.
You can test the urine or there are special ketone/blood meters that test the cat's blood.
We have decided to start tomorrow at 1 unit and see what he is like for a few cycles.
You might even think of dropping his dose down from 1.5u to 0.75U. That would take his current dose, and split it in half between the AM and PM cycles.
Right now, with Stanley's BG numbers being too low to shoot the insulin 2 times a day, he is being left without enough insulin for the evening cycle, or whenever you skip the dose. Without enough insulin, he can not process his food correctly and can continue to lose weight.
There is also a higher risk of ketones developing if there is not enough insulin being given.
Quite frankly, I think the 1U dose you are considering for tomorrow, 13/3/2020 is too much.
It's pretty easy to raise the dose again if needed. It's impossible to take the insulin back out of your cat once you have given the shot.
How often do you test on a daily basis? It is challenging with work but I'm sure we can do more.
Think about your current shot time, think about your work schedule, think about all the other responsibilities you have in life.
Since you skipped the insulin shot tonight, 12/03/2020, you could change the shot time starting tomorrow to an earlier time. If possible, see if you can adjust your dosing schedule to give yourself a chance to test before you go to work. At +1 or even better at +2.
Then, when you get home from work, you could try to get a +10 or a +11 test. Some cats on Prozinc rise dramatically in the last hour, at that +11 time, because the insulin has been "used up ", the duration is less than the full 12 hours.
I have no idea how long your work days are, including your commute. If something we suggest does not work for you and your life, please let us know. We'll try to provide alternative recommendations.
What times you feed when using Prozinc, and other insulins, can make a big difference in the BG (blood Glucose) levels rising in the 2nd half of the 12 hour cycle. So a good suggestion is to try and avoid feeding past about +6. Also, you want to try and have no food available for 2 hours before your pre-shot tests. That is so that the Pre-shot test is not food influenced and you end up shooting insulin into what is a food inflated BG number.