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. Juju says:

    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.

  2. Daisy says:

    We have a skinny, energyless diabetic cat. Vet put us on Adult Light, but one of the main ingredients is grain! Which one of these dry foods then has no grains? And, since the diabetes has now affected liver and pancreas, which product line would be best to put weight on AND not kill with carbohydrates???

  3. Carol says:

    My vet (actually the person at the checkout- I never get to see a vet – I plan on going somewhere else) said my dog must go on the NF diet. She said Purina and Hills sell it. I don’t see NF listed. Would the U/D or G/D possibly what she meant?

    • You are correct, NF is a Purina specialty diet food. Hill’s Pet Nutrition Prescription Diet k/d would be for kidney disease in dogs. Ask your veterinarian if that would be appropriate for your pet’s situation. Thanks for reading!

  4. Sharon says:

    What is the best food for a 70 pound Carolina dog with cutaneous lymphoma and a big appetite! She has lost a couple of pounds on her regular diet and her appetite has increased. She is not following the book, as she is not lethargic and has not lost her appetite. Thanks.

  5. Amy says:

    Can you explain the differences beteeen zd and id? Is the id not hydrolized? My GSD is dying before our eyes and although I fully intend to follow my vets instructions to the T I just want to understand why she may have put Fargo on zd instead of id. I didn’t know there were all of these varieties or I would’ve asked. Thank you!

    • The primary difference is the hydrolyzation and z/d is used when there is, or is suspected to be hypersensitivity to an ingredient. i/d, on the other hand, is lower in fat (there is also a specific i/d formula that is even lower in fat) and more easily digested than many foods. Each Prescription Diet food is formulated for a specific medical condition, although there is overlap in their use. Thank you for reading and good luck with your baby. Keep us up to date on his progress.

  6. Lisa Roi Larsen says:

    Then a/d stands for what?

  7. Barbara says:

    I have an open can of intestinal diet and after labs my vet changed to K/D….is it okay to finish the can of intestinal diet or is the protein content too high?

  8. Kate says:

    FYI – I think you mean “hydrolyzate” not “hydrozylate” for the z/d. Sorry, I’m a chemist so I pick up on these things. Thanks for the explanations, though.

  9. Lance says:

    Went through the Hills Science Prescription Diet website looking for these explanations and they were nowhere to be found.

    Why the secrecy?

    Thank you for describing them.

  10. Pat Walsh says:

    Will the Hill’s z/d wet food help a cat with chronic dandruff?

  11. Quynh says:

    What does the “A” in a/d stand for?


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