Vetsulin dosage question

I have a question about the dosage the vet has prescribed for my old lady Lucy.
Lucy was diagnosed a few weeks ago and has been on 3 units Vetsulin once a day, AM. Went for a check up yesterday and her BG was over 550, so the vet said we need to start twice a day injections; 2 units AM and 3 units PM.

My question is why less insulin in the morning, when she's going to be eating all day, and more insulin at night when she will not be eating. This seems backwards to me, like it should be 3 AM and 2 PM.

I asked the vet why he prescibed more at night and judging by his answer it seemed that was rather arbitrary.

Does anyone have any knowledge or information that would explain this prescription? Is there merit to giving her more in the evening, rather than morning? I am new to this and I know that just because I don't understand the vet's prescription doesn't make it wrong. I am hoping someone can explain and that there is a logical and health related reason.

Many thanks to all for your advice :~)

 

I suspect it was arbitrary. My prior vet did it in reverse with one of Chip's doses on Humulin N.

She didn't know my syringes had half unit markings. I shot I believe 3 units in the AM and 2 in the PM.

If you can eyeball half units, ask the vet if you can split it 2.5U AM 2.5U PM. That's what I did later on, once I found this forum

 

Thanks Dale, that is what I was thinking. I believe I can eyeball half units, or go with 3 AM and 2 PM.
I appreciate your help!

 

You make a reference gauge out of cardboard.

Or take a sturdy metric ruller with millimeter markings, line it up with the bottom of the syringe, and see how many millimeter markings constitute 1 unit, then measure by lining up against the syringe each time.