Hill’s Prescription Diet Cat Food Review

WebsiteHill’s Prescription Diet
Available fromPet Circle  

There’s a lot of controversy about corporate manufacturer Hill’s. Vets endorse it and many would seemingly defend it to their graves, but many pet nutritionists and prominent social media figures in the pet space such as Dr. Karen BeckerRodney Habib, and the Truth About Pet Food’s Susan Thixton are actively against it.

The reason is very simple – Our cats are carnivores, yet Hill’s Prescription Diet dry cat foods are made significantly from grains.

In the Hill’s Prescription Diet cat food review I’ll walk you through the ingredients and composition of one of their formulas so you can easily decide for yourself if it sounds healthy for your cat.

A little background: My personal experience…

When I had my first cat in my 20s I didn’t have a clue what was healthy for him. I fed him a dry food an equally clueless friend recommended, which was easily available at my local supermarket.

At the age of 7 he was diagnosed with early stage kidney failure and our vet recommended Hill’s Prescription Diet k/d. So that’s what we fed him until the day he died.

During that time he became very skinny, frail, and lethargic. For the latter stage of his life he was on other medications, and I vividly remember having to pull his poo out when he had difficulty passing. Like many cat owners, we put it down to “bad luck” or poor old Rodney “getting old”.

We spent a lot of money on the prescription diet and medications because we thought we were doing the best we could for him.

It was a number of years later when, in hindsight, I realised something glaringly obvious – cats are carnivores and the ingredients of Hill’s Prescription Diet is even to this day a lot of grain. Far from what you would expect for a carnivorous animal.

We blindly trusted our vet as a professional, but it is very clear to me now the complex reasons why our vet’s recommend these products. I’ve written more about it here.

If you’re feeding any kind of Hill’s Prescription Diet cat food, or are considering it, then keep reading this review and you can decide for yourself what you think is best for your carnivorous cat.

If you’re still planning to feed a Hill’s Prescription food to your cat, which will very likely be for a specific health reason, then keep reading and I’ll give you a really good tip at the end of the review – so don’t worry if you see Hill’s Prescription Diet as the only option.

Hill’s Prescription Diet review

What the marketing says

Hill’s Prescription Diet, and Hill’s Science Diet, are products of Colgate-Palmolive, a company who have done very well from convincing us their products are necessary for our health and wellbeing.

I shampoo my hair and clean my teeth every day, but do you ever wonder why natives of many countries have amazing hair and teeth without these products?

I’ll put my tin foil hat to one side as I don’t want to go down that rabbit hole, but it’s interesting don’t you think?

Hill’s Prescription Diet Cat Food Review

What can be said about Colgate-Palmolive and Hill’s is they have an excellent marketing and research budget. In fact the research they fund is very influential in the pet health industry, and also very clever.

Consider this – as a product manufacturer do you think they will fund research to (a) promote their products, or (b) convince you another type of diet is healthier, such as raw or fresh?

I hope that doesn’t sound too radical, but I consider it the reason we feed our meat-eating carnivorous cats hard-baked biscuits made from wheat, rice, or corn. Their scientific studies convince us the only healthy option for our cats is baked grain nuggets.

What do you think?

Science or clever marketing?

If you want more to consider, let’s take a look at the ingredients of Hill’s Prescription Diet based on the well known fact our cats are carnivores…

What the ingredients really say

For simplicity I will focus on Hills Prescription Diet k/d, but the same applies to all prescription diets in the Hill’s range. If you’re feeding something else, for whatever reason, then simply take a quick look at the ingredients before continuing with this review.

Did you read the ingredients? What did you think?

Let’s begin…

You’ll find chicken as the first ingredient in the formula, but don’t let this fool you. It actually used to be rice first before they tweaked the formula.

Out of the top four ingredients, which may well be in equal proportions, we have one part chicken to three parts grain – brown rice, corn gluten meal, and wholegrain wheat.

Possibly 25% chicken when we consider those 4 ingredients alone, or less if we consider the others.

That’s not the last of the grain either, as brewers rice as the 6th ingredient may amount to almost as much, and we also see wheat gluten in the ingredients as well.

So that’s a lot of grain, for our carnivorous cats?

We can get a little scientific here ourselves, and see how those ingredients tally with the composition – 29.5% protein, 23.7% fat, and listed carbohydrates of 38.2%.

The first point is 38%+ is carbohydrates, arguably redundant for a cat.

The protein of 29.5% may sound good, but we must consider this is protein from all those grains as well as the chicken. Corn, for example, is very high in protein.

That matters when we consider our cats digest protein from meat more effectively than protein from grains.

Cats have a much shorter digestive tract than us, and shorter than dogs, which means they struggle to process grains sufficiently in the time it takes the grains to pass through their digestive system.

When a cat is fed ingredients which aren’t species appropriate it can take a toll on their digestive system and organs, including kidneys (which ironically is what this formula is supposed to address).

We’ve covered the main ingredients in Hill’s Prescription Diet k/d for sick cats, so you’re probably wondering how that can be healthy or appropriate to kidney disease?

So how does it help those cats? Perhaps it’s better than whatever cat food was fed previously which was possibly even more grain, or harsher grains, which may’ve caused the illness in the first place. Maybe the previous food had chemical preservatives and food colourings?

I really wish all vets would consider what a cat was fed prior to their organs starting to fail. Even better, I wish it was a key part of their studies.

It should be, don’t you think?

Let’s consider the “science”…

Let’s wrap up the Hill’s Prescription Diet cat food review with two of the most common arguments pro-Hill’s from veterinary professionals:

(1) Scientific studies show a cat with renal failure on a renal prescription diet can live up to twice as long.

(2) Scientific studies show the improvement in renal parameters on bloodwork when fed a renal diet prescription diet.

These may well be true, or true in edge cases, but they’re overlooking the most critical factor – What was the cat fed previously?

It’s possible the previous diet was the cause of the illness in the first place, and it doesn’t take much for a “prescription” cat food to be an improvement, or show an improvement in blood tests.

Vets rarely question a cause, only offer a form of medication – i.e. an expensive prescription diet like Hill’s Prescription Diet k/d, or a range of expensive medications or treatments.

With any dietary related condition, the first question a vet should ask is what was the cat fed until this point. If your vet doesn’t ask this, you should question why.

Most scientific studies show an improvement based on a cat being fed one of the many commercial diets formulated from cereals and cereal grains (such as wheat), which means they will almost certainly show improvement when switched to a diet formulated on rice and corn.

Try eating fast food for one month, have your health checked, then only eat microwave ready meals for the next month. Do you think your health would show an improvement?

What about studies which show whether a cat fed a whole prey raw diet is healthier on baked nuggets of rice, corn, and wheat? Why would that be scientifically overlooked?

Well, it wouldn’t help sell the product, would it?

Food for thought?

In my opinion, a cat with a renal condition should never, under any circumstances, be recommended a dry diet absent of moisture.

Which prescription diet should I feed?

One of the most common questions I get asked is which is better, Hill’s (Prescription or Science Diet), or the Royal Canin prescription formulas.

If your cat is suffering a specific illness you are very limited in terms of commercial cat foods.

My best recommendation with both Hill’s and Royal Canin would be their wet food alternatives. For both brands I find these have a much better emphasis on meats and meat proteins, and the moisture content will also be beneficial to your cat over any dry food.

If the wet foods are too expensive, at least have them as part of their diet.

The other option you have is researching a raw or fresh food diet tailored to their health condition. This may also be an option as part of their diet, and may offer your cat better long term health.

Where to buy

For the sake of a price compare the following is for Hill’s Prescription Diet Feline k/d, but should offer a good price guide for different retailers:


Ingredients of Hill’s Prescription Diet cat food (k/d formula):

Chicken, Brown Rice, Corn Gluten Meal, Whole Grain Wheat, Chicken Fat, Brewers Rice, Pea Protein, Chicken Liver Flavor, Powdered Cellulose, Egg Product, Wheat Gluten, Soybean Oil, Fish Oil, Lactic Acid, Calcium Sulfate, Potassium Citrate, L-Arginine, Calcium Carbonate, L-Lysine, Choline Chloride, DL-Methionine, L-Threonine, vitamins (Vitamin E Supplement, Niacin Supplement, L-Ascorbyl-2-Polyphosphate (source of Vitamin C), Thiamine Mononitrate, Pyridoxine Hydrochloride, Calcium Pantothenate, Riboflavin Supplement, Biotin, Vitamin A Supplement, Vitamin B12 Supplement, Folic Acid, Vitamin D3 Supplement), Taurine, Potassium Chloride, Iodized Salt, minerals (Ferrous Sulfate, Zinc Oxide, Copper Sulfate, Manganous Oxide, Calcium Iodate, Sodium Selenite), L-Carnitine, L-Tryptophan, Mixed Tocopherols for freshness, Natural Flavors, Beta-Carotene.

Guaranteed Analysis

Guaranteed analysis of Hill’s Prescription Diet cat food (k/d formula) based on dry matter:

Crude Fibre3.2%
Carbohydrates *38.2% (listed on label)
* May be estimated. Read how to calculate carbohydrates in a pet food.

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3.5 Total Score
Hill's Prescription Diet Cat Food Review

With so many grains in Hill's Prescription Diets for obligate carnivore cats, it really makes you wonder why such a diet would be prescribed or endorsed by vets. Is clever marketing at play? What does the science and research really say?

  • Rice!
  • Corn!
  • Wheat!
  • Wheat gluten!
  • Aren't cats carnivores?

David D'Angelo

David D'Angelo has worked as a scientist since graduating with a BSc (Hons) in 2000. In addition, David holds a CPD accredited Diploma in Pet Nutrition as well as being CPD accredited VSA (Veterinary Support Assistant). However, his experience and involvement in the pet food industry for 15+ years has given true insight into pet food, formulations, science, research, and pet food marketing. Facebook | LinkedIn | Instagram | Pinterest

  1. Hi. Thanks for this. My two cats are sisters and both have been diagnosed with irritable bowel syndrome and have severe anal gland issues leading to infections and abscesses. Lots of very soft stools. Hills gastrointestinal biome dry is their food, with psyllium husk and cooked zucchini for added moisture and fibre to get their weight down a bit. The dry food costs me $50 per fortnight. I can’t afford to add the wet food as it’s even more expensive. I don’t want to just feed wet food – my last two cats would only eat wet and ended up with very expensive dental bills. Can I make my own food? Or what do you suggest? My vets say their condition is genetic and uncommon. They get their glands expressed every three months but I’d like to find a better solution. Thanks.

    • Reply
      Pet Food Reviews (Australia) April 17, 2023 at 6:14 pm

      Hi Pam, I believe these issues are more common than your vet may think. I’m actually surprised they believe it to be uncommon.

      I see dental health as an issue with wet foods in general, and dry for that matter. Cats (and other similar carnivores) keep their teeth clean gnawing on bones, with the simple remedy for that being to add some chicken necks or wings to their diet.

      May I ask what your cats were fed prior to the Hill’s Gastrointestinal?

      Yes, you can certainly make your own food – well worth researching raw food for cats – or even add some raw/fresh to the diet alongside the Hill’s for now, until you feel more comfortable. Given what you’ve said I would expect to see an improvement in their health.

  2. Hi, I’m feeling a bit confused. I’ve followed your website for a few years and fed my cat from your recommendations (grain-free dry food) along with regular raw chicken necks. She’s 19 and now has early stage kidney disease. I’ve spoken to my vet (twice) and they say that these prescription diets are supposed to have grains and rice as that makes them low protein which is the whole point of these foods, to reduce the strain of processing protein by the kidneys. Interested in your thoughts.

    • Reply
      Pet Food Reviews (Australia) November 28, 2022 at 1:35 am

      Hi Kathleen, phosphorous rather than protein is more the issue when a cat has a kidney condition, and some meats are lower phosphorous. Moisture is also an important factor, which is why I find renal diets in a dry kibble form somewhat inappropriate no matter how they’re formulated. The Hills and Royal Canin wet renal formulas I find to be much more appropriate, so they could be worth considering. Alternatively there are “fresh” renal diets on other websites which may help, especially in terms of adding variety and keeping the cost down of (expensive) prescription foods.

  3. Hi,

    The options available can be very confusing and after recently feeding my feline with Hills prescription K/D food, was further confused to find it contained rice and other ingredients which cats should not eat (i.e. rice etc). However, after reading your review above I also came to the conclusion and are reconsidering purchasing any of Hills products again. Thanks for posting the above review, it really helped.

  4. Hi there,
    This site is excellent and helped me improve my cats health and well-being- so thank you!
    One of my cats I fostered and than adopted is on a mixture of Hills I/D and Z/D for his digestive, skin and stomach allergies.
    Have you done any research into these? The wet and dry??
    I have placed him in the advance dry sensitive as due to shipping I am having issues I finding the z/d – so far so good but I’m just wanting to know what will benefit him best to have a healthy and happy life.
    Kelly M

    • Reply
      Pet Food Reviews (Australia) March 28, 2022 at 5:41 pm

      Hi Kelly, I feel many dry foods, particularly those made largely from grains, are not the best diet for a cat as an obligate carnivore. Most Hills dry foods are formulated from grains or starches rather than an emphasis on meat/organs/bones as a better diet for a cat. The wet foods seem much better in comparison to the respective dry foods.

      • Hi
        I read your reviews about Hill’s cat food.I am feeding my cat this food at the moment. She is hesitant when eating it. Could you tell me what I can feed her. She is 15+years

        • Pet Food Reviews (Australia) April 11, 2023 at 2:11 am

          H Jackie, is your cat on Prescription Diet for a specific condition?

      • Thanks! For cats that have skin, digestive and allergies- can you recommend any dry food – I’ve tried a few like vetological and another that was like a dried meet (I think ziwi) but they did not enjoy it even with a slow migration in their usual dry food diet

        • A friend of mine has an elderly cat with all sorts of skin and digestive etc issues that does well on Wellness Core dry, occasionally mixed with Fussy Cat when they can’t afford just the Wellness Core. Anything else they’ve tried so far has caused problems, and the vet diets didn’t alleviate anything. My young cats love Black Hawk which has transformed their coats from rough and dull to shiny and soft since I adopted them, and I occasionally mix in some cheaper stuff, too

  5. My cat has been on the Hill’s Metabolic weight control food for months, at – surprise surprise – my vet’s recommendation. She hasn’t lost weight in that time, she’s gained. I’m no longer surprised, after reading this review. I tried her on a sample of Healthy Everyday Pets but she didn’t like it at all. Now I’m trying her on Applaws. She cleaned up the portion of tuna in jelly I gave her, so fingers crossed she likes the dry chicken as well.

    • Reply
      Pet Food Reviews (Australia) December 17, 2021 at 7:31 pm

      Yes, seems odd Metabolic Weight would be formulated with brewers rice and corn as a weight loss diet for obligate carnivores, but that’s pet food for you.

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