My adult male cat was treated for FLUTD and our vet recommended that I feed him Royal Canin's Feline Urinary SO dry kibble and canned food from here on out. Both of these contain cereal grains.

Before he was treated, I had him on a diet of whatever grain-free kibble was available near me (typically Taste of the Wild or Canidae), supplemented with canned varieties of the same brand.

I would like to return him to a grain-free diet, but I am worried that taking him off of the vet-recommended Royal Canin diet will cause further urinary complications.

Are there any grain-free dietary options I can explore that will reduce the risk of FLUTD as well as (or nearly as well as) the Royal Canin SO diet?

I am open to trying raw meats/offal options so long as they do not pose a risk of exacerbating struvite crystal formation.

  • if your vet have told you to use this food to help your cat you need to do exactly that.asking people over the net to change a veterinary prescribed diet is not a smart thing to do.you need to ask your vet about this and not random strangers. Commented Apr 15, 2019 at 6:34
  • @trondhansen thank you for your input. I will definitely be consulting with my vet before I make any changes. The purpose of asking on StackExchange was to get an idea of what direction I should direct my research so that I have educated questions for my vet. Commented Apr 15, 2019 at 17:56

2 Answers 2


With urinary crystals, flushing them out before they can form to a problematic size is key; struvite crystals are primarily caused by insufficient hydration and alkaline urine. The first step is to move away from kibble, grain-free or otherwise, and switch to a canned or raw diet (depending on what your cat will eat, some will not eat raw foods). Cats evolved to get most of their hydration from food, not standing or flowing water sources; canned cat food is ~75% water, where kibble is ~5-10%. Note that this doesn't mean you can skip out on offering standing/flowing water options; ideally, provide both bowls and one or more fountains for your cat, so he has choices on which to drink from.

Grain free will be the next consideration when choosing the new food options; most higher-end foods will be grain free, but as always, read and understand the labeling before making a choice. Higher meat content foods will result in a more acidic urine, helping to prevent crystal formation; the plant matter (cereal grains, etc) in the prescription diet skew the urine pH toward alkalinity.

If your cat is particularly prone to crystal formation, you may also wish to look at lower-phosphate foods, however, this information can be difficult to find from most manufacturers, and is rarely on the labels themselves. You'll need to look up charts compiled by the company, which may not be available.

While in most cases, it's worth understanding and keeping your cat on a vet-prescribed diet, unfortunately, in the case of Royal Canin Urinary SO, the "secret ingredient" is extra salt to attempt to provoke the cat to drink more water; it's much easier to introduce hydration to the cat via food than the feline equivalent of free bar snacks. Do speak to your vet about the change in food, anticipate some pushback, and agree to additional monitoring the cat if needed during the dietary change. I've been in your situation in the past, with the same prescription diet, and found definitive positive results in my cat's health by moving him from SO to a grain-free, meat-based, canned diet; the results were proven out by subsequent urinalysis performed by a skeptical veterinarian.


Grain free does not mean carbohydrate free and carbs are what you want to avoid in cats who have FLUTD. Also stop all dry food whether or not they are prescription diets. Dry food is loaded with carbohydrates which creates an alkaline urine, increases specific gravity of the urine and allows struvite crystals to form. Feeding an appropriate diet high in protein creates an normal acidic urine that creates an environment that makes it impossible for crystals to form. Your vet should know better in this day and age.

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