Cat question: opinions on protein levels

Our 15 year old has diabetes - though it may be wholly or partially pancreatitis. The question is about protein levels in food. I switched him (and the others) to a grain free food - which they love - but my Vet wants me to lower protein levels to keep the old fart’s kidney function up. I’ve been reading about this and it isn’t clear what to do so I’m asking for opinions. His kidney levels have been mostly fine - urea is sometimes up but not a lot. BTW, the cat has gained back 3 pounds of the weight lost when he developed high blood sugar and he seems incredibly fine though he still drinks too much. That may be because his blood sugar is still too high as we dose him with antibiotics and wait for pancreas test results. He’s getting insulin so maybe that’s why his weight is back up.

They’re eating dry food. I’d like to switch to wet but we have issues with other cats - including a feral who comes in to eat (and run).

One of our cats had severe pancreatitis about 6 years ago. At that time, all 3 cats were eating dry food but as I researched causes of pancreatitis in cats, it seemed many agreed that dry food was bad for cats for many reasons.
Anyway, I switched everyone to Wellness canned grain free food, chicken and turkey, and the pancreatitis resolved.
I know you aren’t sure your cats problem is pancreatitis, but I’d give switching to canned food a try.
Many believe even diabetes in cats is indirectly caused by dry food.
Now switching food was a long drawn out process, much resistance, especially from the sick kitty who LOVED dry food (aka kitty crack), but I think they are healthy today because I switched away from dry food.
Sorry this is so long, but I hope it helps.

We had an old cat with diabetes. Just refused to eat canned food. The vet let us switch to kitten dry food. It provided a good amount of protein but did have some grain and fat in it. We also gave him human fish and chicken.

Grain free does NOT mean carbohydrate free – it just means no wheat, corn, or rice. When they make a dry kibble, it has to be stuck together with something – for the grain free foods, that means chickpeas, peas, sweet potato, white potato, tapioca, etc. There’s a pretty big range of protein levels, even within the grain free foods. For example, Blue Buffalo makes Wilderness which is a high protein grain free, and Freedom which is has protein levels closer to traditional kibbles with grain.

You just have to read the labels and figure out what works! Visit your LOCAL INDEPENDENT PET STORE and ask for someone to help you with the cat food, telling them what your issues are and what your vet is recommending.