If you are using a human meter, a number between 40 - 120 is normal. That's what you'd see if you tested a non-diabetic cat. Bob's been off insulin for a year and a half, and when I test him, I usually get a number in the 70s.
On a vet meter, or a meter designed specifically to test cats like an Alpha-Track, we usually put the normal range at 70-150. About 30 points higher than a human meter. So the vet saying 150 is "low".... well, a diabetic reading 150 would be just above "normal", so in some ways, that might be considered "low" because they are almost in non-diabetic numbers. But it's the high end of the normal range. 200, no matter what meter you're using, isn't low.
When someone is new to treating feline diabetes, and just starting home testing and giving insulin, we usually recommend that they not give a shot on any number below 200. That is primarily because you haven't collected much data yet to determine how effective the insulin has been. It's a "safety" thing. But we don't say that because it's a low number. Just sort of low to give insulin on when you're just starting out. Once you have data that shows what a given dose has done, it's very common to shoot numbers like 150 or even lower. Just before Bob went "off the juice", I gave insulin on numbers under 100 on a few occasions. But they were very small doses, and I'd been doing "this" for a while. A lot depends on which type of insulin you are using too.
Carl
