Phosphorus binders do have side effects and should be used only when necessary. Dr. Pierson has mentioned here before that they should only be used if the phos level is a 6 or higher.
Here is a great resource to help you understand your cat's values:
http://www.felinecrf.org/how_bad_is_it.htm. Tanya's page can seem overwhelming because there is so much information there, but it is an amazing resource for information on CKD.
While the creatinine is very high, so I'm wondering if other possible causes of the high creatinine explored? Was he tested for ketones, pancreatitis? Has he shown any physical symptoms other than the high bloodwork? If so, what were they? Bloodwork gives us an indication things are wrong, but symptoms and behavior give a better view of what might be wrong. Even though some cats may have some higher numbers, that does not necessarily mean they are in end stage renal disease. In the "how bad is it" link I provided, make sure you scroll down and read the section titled "End Stage Renal Disease (ESRD)".
Also, what are his BG numbers like? Are they normal at home? Is he still in remission?
There are various secondary treatments for CKD you can employ, and they are usually based on the exhibited symptoms. Check out this page:
http://www.felinecrf.org/treatments_essential.htm. As for renal supplements, my advice is to save your money, because the ones that are safe have not been proven to have any real effect on managing the disease, and there are several that are actually potentially harmful for CKD cats. See here:
http://www.felinecrf.org/holistic_treatments.htm#standard_process_products
There are several commercial foods that are good for both CKD and diabetes. To manage diabetes, you want to feed a low carb (less than 10%) canned food, and to manage the kidney disease, you want to feed a high quality, low phosphorus canned food. Many vets simply recommend low protein diets for cats with CKD, because they are by default low in phosphorus. However, it's the quality of protein and phosphorus levels that matter, not the protein values. The low-protein prescription kidney diets have only been shown to be beneficial in end stage renal failure and should not be fed long term. In fact, they cause muscle wasting are completely inappropriate for most CKD cats. You may want to consider them for an end stage cat to alleviate some of the symptoms, but keep in mind that end stage cats are usually very picky and the low protein diets don't taste so good to them, so usually you need to feed the cat whatever it will eat. Keeping the cat eating is priority one, regardless of the type of food.
Here's an updated food list with the values listed in order of phosphorus:
http://www.catinfo.org/docs/Food Chart Phosphorus 9-22-12.pdf. You're looking for something with less than 10% carbs (for the diabetes) and less than 250 mg/kcal of phosphorus (for the kidneys). The foods I would suggest in your case are Merrick's Before Grain Beef, Merrick's Before Grain Turkey, Wellness Turkey, EVO 95% Chicken & Turkey.
If those are out of your price range the next best thing to feed are the low carb Friskie's Special Diet Turkey & Giblets and Salmon flavors. However, I would strongly urge a food without byproducts, and keep in mind that they're still cheaper than the prescription foods and usually about the same as many grocery store brands if bought in large cans or in cases. Studies have shown that the quality of the protein source does make a difference in controlling the disease, and that needs to be considered along side phosphorus content. Better quality protein reduces the amount of protein metabolism residue which means the kidneys to work less.
Keeping your cat well hydrated is also key in managing CKD, which means NO DRY FOOD. At all. Dry food is moisture depleted and causes chronic dehydration in cats, often the cause of CKD as cats progress in age. Adding a little water with the canned food portions helps, as do pet fountains, since they encourage cats to drink even when they are not thirsty (cats have very low natural thirst drives, so by the time they seek out their water dish they're already dehydrated).
I know I've just thrown a lot of information at you, so if you have any questions about anything, please ask!
