Is he spraying or squatting, and is he peeing and pooping outside the box or just peeing? You could try a larger, lower litter box, maybe new litter, and place disposable pads around the box to make cleanup easier.

It could be he no longer likes the litter. It happens..........

I recommend trying a different sort of litter pan set up near the first. If the current pan is high sided, he may need one that's easy to stroll into and out of. If it's too short or narrow for him to comfortably turn full circle in, a larger length and width are needed.

As for litter itself, he may associate it with the discomforts he may have had before his diabetes was treated. You can try adding Cat Attract, which is a litter that has stuff added to make it smell more like a cat would like to use. It's a clay litter, but you probably only need to use it once. I did, even though I don't use clay litters. The one cat just wouldn't use the pan for peeing after his illness, and the vet had ruled out other possible reasons for avoidance. It was added to the regular litter, he used it immediately, then never a problem after. It's been a few years since I tried it.

You could offer a large low sided pan with pee pads instead of litter. After a pee, roll up the pad and toss. I know someone who offered a pan with NO substrate at all. She just poured the pee into the toilet and washed the pan after each pee.

Are you testing his blood glucose at home? You really should in order to get on top of his insulin needs.

Would the vet consider anti-anxiety medication? Maybe you could try Feliway.

My own husband would be euthanised if he dared to bring up killing a pet just because its illness is annoying. His attitude can be felt by your cat, adding to the cat's anxiety and contributing to the problem.

I hope that shomething here is of use to you.

He is squatting, and hes not pooping outside the box. He poops in a diffeerent box most of the time but he is peeing on the floor next to that one now too. I am using the disposable pads. Where do I get the cat attract? I have 4 cats and 5 cat boxes. He will use 3 of them and pees beside each of them, but here again not always. Hubby really loves Abby (abner) he's the one that brought him home. The cat did live in his Mothers basement for two years. When I mentioned the problem to her she said "oh yea" he did that here a few times too. AAAARRRRGGGG

I think its available at any big box store. Have a google on it. Most pet supply places carry it.

That this is a life long habit is infuriating. I have one cat, abandoned here at Christmas two years ago. If he isnt given the option of going outdoors for a few minutes every few days he pees next to the pan. He goes out when I need to work outside and comes right back in with me. If its really horrendous out, a look out the open door is sufficient. I have no idea why hes like this! He is a real sweetheart. I wonder if Abner might respond as well to a few minutes supervised outdoors time, too. I am not one to condone cats being outdoors, but this works and Simon has always been near enough to respond immediately when I call him in.

If you havent already done so check out felinediabetes.com - one of the best online communities EVER. Those folks will have lots of suggestions - they've been there done that.