It happens. We will see where he is tonite. Important thing is you didn't shoot again. The current high BG levels you are seeing could be fur shot or they could be a "bounce" off his low.. explanation below.
Has the vet checked him for pancreatitis or mentioned exocrine pancreatic insufficiency? Both can cause diarrhea.
Wendy
Bounces - what are they and is my cat doing them?
When a cat isnt regulated, the blood glucose has probably been high for a while. As the insulin starts to take effect and numbers start to come down, the liver has to learn to adjust to the lower numbers. We call this "liver training school". But before it relearns that low numbers are ok, when the BG drops to a number lower than the liver is accustomed, or if BGs drop low, or if the BG drops suddenly, the liver”panics” and reacts by releasing counterregulatory hormones and glucagon. This drives the BG back up. This is what we call a "bounce". Bounces can take up to 72 hours to clear so we are generally careful about increasing doses during the bounce. Once the bounce clears, then you can see the "real" numbers and determine if the dose needs to go up or down.