Re: Cat is off Insulin, very skinny
The weight loss is one concern and I would ask the vet if the last blood work included thyroid tests, which can explain weight loss.
Of course uncontrolled diabetes (and cancer) is also a common cause of weight loss.
How are his teeth? - when my civies teeth/mouth are bad, he doesn't eat well. Also could be a source of infection=elevated WBC possibly?
Not pooping can become megacolon. When you palpate his stomach/belly, does it feel soft and squishy, or do you feel large firm intestines, almost like banana inside his belly? My cat has megacolon with difficulty pooping and after trying a large number of things, I finally have control of it using Miralax and increased fluids.
Miralax is sold over the counter, in grocery or drug stores for human use (with constipation). It is a white powder which you sprinkle on every meal you feed. It is tasteless and acts by drawing water into the colon, thus softening the poop. You must increase kitties water intake when you give miralax, so I add a lot of water to his food and sometimes syringe extra water into his mouth.
It will take 3-4 days to work its way through his system before you see its results. If kitty is really blocked up he may need 1 or more enemas to get moving first, because miralax only softens the poo from the food its in. Most kitties that use it here seem to need somewhere between 1/8 teaspoon-- 1/4+teaspoon added to 5.5 ounces of food. Unfortunately, getting the right dose takes a couple weeks, and you will probably need to give too much (messy), then back off gradually. Miralax is ok to use with diabetic kitties, so long as you increase water, so they don't become dehydrated.
If the constipation is severe and /or dehyration is an issue, I have had a lot of luck giving lactated ringers solution subcutaneously everyday. Depending on your cat, and you, home enemas are a life saver.
Good luck