Hills Science Diet Prescription Diet Feline C/d Dry

Just how safe is the food you feed to your cat? A review of a food commonly suggested by Veterinarians.


In short I consider Hills Science Diet Prescription Diet Cat food to be a lower quality food, marketed cleverly through veterinarians offices, loaded with ingredients that are known to be dangerous to pets, and sold at an over inflated price.  In this review we will cover their c/d Dry food, as marketed for urinary tract health.


The long and the short of it is that this food is suppose to be good for cats who suffer from lower urinary tract problems. There are several dietary, contributing facts to cats developing this problem, one is moisture intake, one is high calcium intake, and the other is too much magnesium.

It should be noted that at one time people considered “Ash” as the contributing factor, however Ash is where the minerals are found, including magnesium.

Cats are true carnivores, they need a good meat source in their food, and it should always be the top ingredient. Sadly this food has no real meat source, the closest thing to meat is Chicken By-Product Meal, and that is the second ingredient, after Brewers Rice.

Let us ignore the obvious problem of rice as a main ingredient and skip to the chicken by-products. Chicken by-products can feet, egg shell, intestines, even cancerous tumors, and to a lesser extent, feathers. Although cats fending for themselves would eat these parts, they would also eat a considerable amount of meat, and it is the meat that this food does not even use. An actual meat source would be something like Chicken Meal.

To make matters worse, by-products are preserved with Ethoxyquin, a dangerous chemical pesticide linked to many health problems in pets. It is considered part of the by-product and as such is not listed on the ingredient list. Ethoxyquin is banned from use in some countries (such as Japan) due to its risks. You will note we do not use this to preserve human food.


Now back to the rice. Brewers rice is a cheap carbohydrate, it does not contain nearly the nutritional goodness of whole grain brown rice. It is a common allergen in cats. Rice, of any kind, should never be a top ingredient in a cat food. In effect brewers rice is the left over parts of rice after making beer, and it may contain hops. So basically the first thing a cat is eating is something cats shouldn’t be eating at all.


The third ingredient is Corn Gluten meal. Again this is a cheap filler, and one that causes allergies in some cats. While corn really shouldn’t be in any cat food, it certainly should not be in the top three ingredients, and Corn Gluten Meal of all things isn’t even full corn, its the waste left over in making corn syrup. There isn’t even any corn bran. Corn meal, also not great for cats, but as it contains the bran it is considerably better than Corn Gluten meal.


As we skip through the ingredient list we see things like Chicken Liver Flavor.. and wonder why not just use actual Chicken liver, at least that would be meat. I guess they have to put something in the food to encourage pets to eat it. This would explain the Pork fat.


At the bottom of the ingredient list we see the cheap preservatives BHT, and BHA. Again these are not used in the better foods and have been linked to various health problems in pets. Oddly enough, among other things, both are linked to cancer in the urinary tract system.

When Hills started making pet food it was quite high quality but as of 1976 when they were purchased by Colgage Palmolive the quality declined in many peoples opinion.

Would I feed this food to my cats?


Not on your life. In fact I am not fond of any of the Hills products. For the most part they are highly over priced for the quality, having pumped money into getting veterinarians to endorse and promote the food. No doubt about it, this food is cleverly marketed, but an educated eye can pin point problems in the ingredients list at a glance.


I want to assure people who are feeding this food at their veterinarians suggestion, that their vet is likely innocent and unaware of how poor this food is. For the most part they are not pet nutritionists, and have been told by Hills reps for years how wonderful this food is and that it is the only food they should promote. They rarely get any education on ingredients other than that from the Hills representative, who typically come with lots of promotional gifts (mugs, shirts, even scholarships) to encourage loyalty from vet students in training.


Most premium cat foods (none of which are sold in grocery, or department stores) with quality ingredients and a low magnesium content (below 0.08% ) will help. Look for foods with a good meat source, and no by-products, no cheap filler, and no cheap preservatives. Find a food that uses human grade ingredients. You may even find a much better food at a lower cost.

Additionally help your cat increase its water intake, keep water fresh at all times, use a stainless steel, or ceramic bowl. A cat with urinary tract problems should also be offered a small amount of canned food at least twice a day, with water added to make a soup, as this will help keep its urinary system healthy.

Overall I would rate Hills Science Diet c/d as a 4 out of 10 – a very overpriced food for its poor quality.

File:Rsgranne - Cats cats cats! (Arrow Rock, Missouri, 20050703) 03 (by-sa).jpg

photo source (NOT my cats)

Crude Protein: 30% min.
Crude Fat: 13% min.
Crude Fiber: 1.0% max.
Moisture: 10% max.
Ash: 6.5% max.
0.5% calcium, no more than 0.4% phosphorus and 0.08% magnesium, and 0.1% taurine

Brewers Rice, Chicken By-Product Meal, Corn Gluten Meal, Pork Fat (preserved with mixed tocopherols and citric acid), Chicken Liver Flavor, Potassium Chloride, Choline Chloride, Calcium Carbonate, Calcium Sulfate, Iodized Salt, Vitamin E Supplement, vitamins (L-Ascorbyl-2-Polyphosphate (source of vitamin C), Vitamin E Supplement, Niacin, Thiamine Mononitrate, Vitamin A Supplement, Calcium Pantothenate, Riboflavin, Biotin, Vitamin B12 Supplement, Pyridoxine Hydrochloride, Folic Acid, Vitamin D3 Supplement), Taurine, minerals (Ferrous Sulfate, Zinc Oxide, Copper Sulfate, Manganous Oxide, Calcium Iodate, Sodium Selenite), preserved with BHT and BHA, Beta-Carotene.

Other Cat Food Reviews – From Worst to Best of currently Reviewed Foods (there are better there are worse)

Purina Cat Chow 

Summit Three Meat

President’s Choice Nutrition First Chicken & Brown Rice

Related Links

What is in Your Cats Food?

Big Cat, Little Cat, why some cats are thin and some are fat

Why is my Veterinarian Selling me this Pet Food?

How to Reduce Shedding in Cats

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User Comments
  1. AJ

    On May 16, 2010 at 11:20 am

    You say veterinarians don’t understand pet nutrition (an assertion with which I disagree). You are entitled to your opinion.

    What concerns me is that I do not see anything in this article that explains why anyone should believe your position.

  2. wendym

    On May 16, 2010 at 3:24 pm

    Although I’m a dog owner AJ, I know that B Nelson is right in her assessment and if you give her review a re-read I think you’ll see her assertions are spot on.

    Excellent review. Out of curiosity how does this brand measure up for taurine content since it’s so low in meat?

  3. AJ

    On May 16, 2010 at 6:03 pm


    I too am a dog owner, but am interested in pet nutrition.

    My question for B Nelson is this: What makes your opinion on the subject valid and based on the assertions in your article more valid than the opinion of a veterinarian?

    It is an honest and well intentioned question. I am not trying to provoke. I want to know what B Nelson’s qualifications are. There are a lot of people out there in internet land who put out “information”, but a lot of it is bunk. It is important to figure out what out there is real based on research and study and what is someone’s opinion being passed off as fact.

  4. wendym

    On May 16, 2010 at 7:31 pm

    I understand AJ, I guess I’m blinded a little because I have interacted with the Hills merchandisers and reps, and I have heard their sales lines regurgitated (sometimes word for word) from my own veterinarian. Don’t get me wrong, our veterinarian is fantastic when it comes to dealing with illness and injury– I have just surmised that when it comes to nutrition and allergies that I have to take the bull by the horns and read reviews (like this one) and research the data myself instead of relying on hearing from my vet the Hills (or Nutro) sales pitch du jour.

    I don’t say this against all veterinarians, as some do take a special interest in animal nutrition and study it extensively– however they are human and must manage their time and continuing education resources as best they can, and sometimes that means compromising in one area while excelling in another.

  5. flame007

    On May 17, 2010 at 2:03 am

    very good

  6. Brenda Nelson

    On May 17, 2010 at 11:22 am

    to AJ
    I have attended College and taken many classes on Pet Nutrition including Ingredients and changes in brands, like Hills going down hill after being bought out, same thing happened to Iams,…

    the evidence is right there on the side of any bag, it tells you the ingredients plain and simple, anyone with knowledge on what the ingredients are can see its a bad food.. anyone who knows cats are carnivores can simply see this food is not quality.

    as for taurine it contains the minimum required amount .1% taurine can come from other sources but is not as digestable, I assume this was in the by-products.

  7. AJ

    On May 17, 2010 at 12:49 pm

    B Nelson,

    Thank you for taking the time to answer. I am truly not trying to provoke, but I don’t rely on everything posted on the internet as truth and am very skeptical of articles like yours where the credentials of the author cannot be found in or attached to the article in question.

  8. Brenda Nelson

    On May 17, 2010 at 9:04 pm

    AJ – no problem
    I included the ingredients of the food to make sure people can see it for themselves, and all I did was explain what these ingredients are ..basically anyone can look up the information on their own too.. meaning that if anyone wants to look up more information about what brewers rice is, or byproducts, they can..

    premium cat foods always use chicken MEAL as the number one ingredient, since cats are carnivores.. and the best never use by-products, BHT, or BHA.

    for the record, I own cats, pet hair sheep, a donkey, llama, chickens and pigeons… and a few other pets too, but no dogs.

  9. sara20

    On May 18, 2010 at 1:54 am

    Nice to read this piece.

    Keep writing more about it. It is really gracefully and very well written skill.

    Thanks for sharing.



  10. Daisy Peasblossom

    On May 18, 2010 at 8:28 pm

    I’ve done a little research of my own, and one of my co-workers raises show cats. She has nothing good to say about Science Diet; and I’ve read their labels. Definitely not impressive! I’ve noticed that the ingredient list on most pet foods have gone a notch or two to the worse this year while becoming significantly more expensive. What I would love is the name of one or two good books (with recipes if possible) on feline nutrition.

  11. PR Mace

    On May 19, 2010 at 4:04 pm

    Since I don’t have cats, I will forward this article to my daughter and her three feline family members. Thanks for the time and research you put into this article, it shows.

  12. Angela Riedel

    On October 12, 2010 at 6:05 pm

    Hello B,

    I was so relieved to see your page on Hill’s so called “Prescription Diet” c/d for cats. I am disgusted by the frankly fascist marketing of this ordinary mass produced cat food. I don’t have to tell you about the clamp down/control scheme of their marketing, it’s offensive and ridiculous. At any rate, my poor cat nearly died last month from these urinary crystals and it cost me over one thousand dollars for emergency care. This can’t happen again. All they said was to feed him this Hill’s brand food but it’s so hard to get that it’s stupid. I’d much rather feed my cat something of better quality and am writing to ask you if you could please recommend something. I have no idea where to go to get valid, realistic, and honest information on this subject. Veterinarians have become controlling dictatorships, as has the medical industry in general. You may not agree but that is neither here nor there. You do understand how nasty pet foods really are and I am asking you for your opinion because you’re not profiting or pushing anything. Could you possibly make a couple of suggestions for me, or
    at least point me in the right direction to find legitimate information that will help my cat stay free of those terrible, painful crystal formations? I would really appreciate it and would gladly pay you for your time and trouble if necessary.

    Thank you very much.


  13. Brenda Nelson

    On October 12, 2010 at 10:20 pm


    I mostly agree with you but sometimes the vet really doesnt know any better, they were brainwashed to a degree by the food company representatives.

    Orijen is a terrific food – Nutram (only in Canada as far as I know)

    of course you could be anywhere in the world, so not sure what brands you have and what you dont..

    giving your cat water in its wet food – makeing soup, will help though.

  14. Laura

    On November 16, 2010 at 12:46 am

    My cat suffered from urinary infections, he’s eating C/D now, he’s been fine for 4 years. I might not have a lot of knowledge about ingredients or marketing strategies but I know it helped my cat, so I’m sticking with it

  15. Carnivores

    On December 5, 2010 at 1:57 am


    How about the fact that cats happen to be the strictest of all carnivorous mammals?

    How about the fact that a cat has NO teeth which are shaped to grind?

    How about the fact that a cat’s jaws do NOT rotate — as in to chew — which is why nature designed them to TEAR & shred meat.

    How a veterinarian, somebody with advanced education beyond high school, can tell people to feed foods not only too high in carbs for an obligate carnivore, but in DRY cereal form, is the question you OUGHT to be asking people.

    Bet you know at least three people whose cats have the oh-so-common vomiting issue. Wow, wonder why that is …

  16. Darlene

    On June 22, 2011 at 2:38 pm

    I am an owner of 3 dogs who has recently switched to Champion Foods (Orijen and Acana) from Hills Science Diet products (TD and ZD). I trusted my vet’s assertion that Hills has nothing but quality ingredients, which made sense given the high price.

    Once problems developed with my dogs (skin in the TD dog and gastrointestinal in the ZD dog) I began researching ingredients. Hills ingredients are very substandard, in line with grocery store dog foods, not premiums brands that are at the same price as Hills. For a good understanding of what the ingredients in dogfood are, check out the following link from AAFCO (Association of American Feed Control Officials):


    This site really helps when reading an ingredient list on a bag of dog food.

    My dogs are doing much better, skin has improved, no more clearing the room from my ex-ZD dog :) and no more eating of feces (unexpected benefit!).

    Well written article, by the way.

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