Hill’s Prescription Diets Alphabet Soup

The acronyms for Hill’s Prescription Diet foods are not difficult to figure out. The “d” always stands for diet. It was easy in the old days, before there were so many different Prescription Diets. c/d was “crystal diet,” k/d was “kidney diet,” and h/d was “heart diet.” If memory serves me correctly, when I graduated in 1980, that’s all the diets there were.

Why is this bag empty and crumpled? Pearl LOVES her Prescription Diet k/d.
Why is this bag empty and crumpled? Pearl LOVES her Prescription Diet k/d.

Now, few letters go unused.

We discussed a/d yesterday.

b/d is for “brain diet,” and contains ingredients that help dogs who have dementia problems, especially from liver disease and old age.

The nutritionists at Hill’s figured out that not only could struvite problems be solved in cats by feeding a special diet, a dog-formulated diet would work for canines, too. Canine c/d was born, and the “c” still stands for “crystal.”  Click here for explanation of struvite.

d/d is for “dermatology diet,” and there are several formulations for patients who need a special diet for food allergy.  d/d can also be helpful for certain gastrointestinal problems.

g/d is for “geriatric diet” and is also used in certain cardiovascular and kidney diseases.

h/d is for “heart diet” and is formulated with low sodium for patients with cardiac problems.

i/d stands for “intestinal diet” and is effective for patients with a variety of gastrointestinal problems. It is highly digestible, making it ideal for pets with “sensitive stomachs,” and low-residue, so it’s excellent for constipation problems because less total stool is generated.

j/d is one of the newer foods and is formulated with neutraceuticals to enhance joint health through stronger cartilage.

k/d was Dr. Mark Morris’ very first food formulated, though, of course, new formulations have been created as research reveals more and better ways to care for patients with a variety of kidney diseases.

l/d is for “liver diet” and contains ingredients to help with a variety of liver problems including cirrhosis and copper storage diseases.

m/d is a feline-only formulation that is Hill’s lowest-carbohydrate food. It is the diet of choice for diabetics and cats with obstipation.

n/d stands for “neoplasia diet,” and is “clinically proven to increase survival time and improve quality of life for dogs with cancer undergoing chemotherapy or radiation treatment.” [Hill’s Key To Clinical Nutrition.]

r/d is one of Hill’s biggest-selling Prescription Diets because, as in people, obesity is epidemic in animals. Reducing diet is high in fiber, yet low in calories, so pets get to have a large meal, keeping them full, while also gradually taking weight off.

s/d is a “stone-dissolving diet,” discussed in detail in an earlier article.

t/d stands for “tooth diet” because its formulation and physical characteristics are both special. The formulation contributes less to the physical and chemical components of plaque. Also, fibers are laid into the food that squeegee each tooth that bites into the food.

u/d can non-specifically be called “urinary diet,” but it’s actually a food for pets whose kidney failure has progressed to an extreme level. However, u/d is also helpful for dogs predisposed to calcium oxalate urinary bladder stones.

w/d is kin to r/d in that it is a “weight-control diet.” w/d, though, is for dogs and cats who have lost the weight and are now ready for a maintenance food. It is high in fiber, but not as low in calories as r/d. It is also fairly low in carbohydrates and is often used in canine and feline diabetes.

x/d is a feline-only food designed to prevent calcium oxalate bladder stones in cats.

y/d is also feline-only, and is used for controlling hyperthyroidism in cats.

z/d (you thought we’d never get there!) gets its “z” from hydrolyzate. Proteins an immune system has never seen are needed for food allergy patients. It is also unique in that its proteins are hydrolyzed, making it difficult for a food-allergy-primed immune system to respond to them.

There you have it, the entire Hill’s Prescription Diet alphabet soup.

Aren’t you glad Hill’s Science Diets just have regular names?


  1. Thank you for this! I was very confused by the c/d and u/d foods. This helped a lot. My girl, Penny, is going to see the vet again tomorrow. She was last seen and treated for a UTI and crystals at the beginning of January and now, end of February, may have another. It’s hard to know if she was the one with bloody urine when we had 6 dogs present! She is the most likely candidate. Playing it safe and taking her in with her history. She is overweight and I’ve been trying to work on her weight for a while. She’s been on the science diet perfect weight off and on and when she is on it, she does lose some weight. I JUST ordered a new bag of the perfect weight, of course. In your opinion, if my vet does recommend the c/d food, should I feed a bit of the wet food with it as well? She is in the crate for 8 hours a day during the week and unfortunately, I cannot get home to let her out more and I don’t have any resources to hire anyone else. I also worry sometimes that she doesn’t drink enough. Would the wet food help make sure she is getting more liquid in her diet?
    The other concern is she is very stubborn about going potty. She is potty trained, but she chooses to hold it for far longer than she should sometimes. I will have to stand outside and watch her and continue to tell her she has to go pee. Otherwise, she will just come in the house and hold it. She’s been this way since she was a puppy. Any thoughts on that?
    Thank you!!!

    • Canned food can increase water intake substantially. I don’t have a “fix” for not wanting to “go,” but, you’re doing the right thing staying outside with her until she goes. Maybe that will eventually register with her. Thanks for reading, Dr. Randolph.

  2. My dog has oral metastatic melanoma and the vet recommends us trying hills prescription diet N/D but we cannot find it anywhere. Does anyone know if it has been discontinued ?

  3. My male orange tabby cat is on Hill’s c/d multicare. He prefers the “stew” version to the pâté. The problem has been that there seems to be a shortage of this. It’s usually in the smaller 2.9 Oz cans. Every place I’ve been to says it’s on back order.
    Can he have the c/d multicare Stress version without any problems? At least THAT is available.

  4. What is the difference between x/d and c/d?
    We have two cats, one requires prescription food. Outside of cost, is there any reason why our second cat cannot/should not be put on the same diet?

    • I couldn’t find reference to x/d in any of my Hill’s Pet Nutrition literature. c/d has a nutritional profile suitable for almost all life stages. The only contraindications for Feline c/d are patients on urinary acidifiers, growth and pregnancy. Here’s a valuable tip: You can call the toll-free number on the package and ask a Hill’s representative ANY question. They have a lot more nutritional resources than I do and they may be able to guide you on x/d. Thanks for reading, Dr. Randolph.

  5. My cat just got diagnosed with fatty liver disease. He is still in the hospital getting treated and hopefully we’ll be home here soon. I’m trying to be proactive and get his new dry and paté food. I don’t know what type of food to get him. What would be your recommendations of dietary cat food for a cat with fatty liver disease?

    • There are many factors to consider when choosing an ill pet’s diet. The doctor treating your kitty has ALL of the information on your cat and will advise you on the best food. Thanks for reading, Dr. Randolph.

    • That would be a call for the doctor who is treating your kitty, guided by the degree of his thyroid disease and his kidney disease. Thanks for reading, Dr. Randolph.

  6. I can’t thank you enough for this article! Why can’t Hill’s have this exact information in one nice neat FAQ on their site? My dog is old, got pancreatitis a couple years ago and was put on digestive i/d wet food. Since then we add to the wet food about a 1 T of i/d dry food hoping we will get a couple crunches to keep her teeth healthy, but she has always swallowed hard food whole. LOL And we add about 1 T cut up boiled chicken breast to the mix, and sometimes 1T whole grain brown rice if any was made. So I was familiar with i/d. But her last blood test showed huge improvement so the diet is working. I noticed the dry digestive i/d food actually had a higher fat content than it should, at 14.8%! So I was looking for other Hill’s options for a geriatric dog needing lower fat. Oh my goodness, I couldn’t keep up with the acronyms prefixes and couldn’t find definitions on Hill’s site.

    So thank you for your article. So very helpful even 11 years later!

    • We’re happy to help. A couple of suggestions: 1, Don’t add chicken, rice or anything else to the food. Adding ingredients has the same effect as removing ingredients, it imbalances the diet. 2, You can’t compare the fat content (or any other analysis of the food) between dry and canned. It’s truly apples and oranges because of the moisture content. I’m delighted that her blood test results are showing improvement. Keep it up! Thanks for reading, Dr. Randolph.

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