Petaluma vs. Hill's Prescription Diet k/d: Choosing a Kidney-Friendly Food for Your Dog

By Caroline Buck, Co-founder of Petaluma

Your dog's bloodwork came back with a kidney value flagged, and your vet mentioned Hill's Prescription Diet k/d. Or your senior's numbers are still normal, and you want a food that is easier on the kidneys. Either way, you are probably shopping for a lower-phosphorus food.

Hill's k/d is a well-studied kidney diet. It also changes how you shop. Until now, you could probably buy whatever food you or your dog liked, at a store or online. A prescription diet needs your vet's approval before it ships, and it costs more than a regular food. At 1-800-PetMeds, k/d runs about $5.09 a pound, and Hill's Science Diet Adult runs about $3.47.

So many pet parents ask whether a premium, non-prescription food that is naturally lower in phosphorus could work instead. The answer depends on how far along the kidney changes are.

Here is how k/d works and when a prescription kidney diet is the right call. We also look at where a low-phosphorus everyday food can fit, using Petaluma's Whole Food Mixer as the example. If you are new to Petaluma, we make complete dog foods formulated by veterinary nutritionists, with plant proteins like soy and peanut in place of meat.

What Hill's k/d is and how it works

Hill's k/d is a therapeutic kidney diet that lowers phosphorus, protein, and sodium to ease the workload on damaged kidneys. The dry chicken recipe lists 0.29% phosphorus and 15.6% protein on a dry-matter basis, which is how vets compare foods with different moisture levels. Both figures come from the Hill's product page.

Phosphorus is the main target. Healthy kidneys clear extra phosphorus from the blood, and failing kidneys cannot keep up. The IRIS treatment recommendations, the staging system most vets use, set blood phosphorus targets for each stage of chronic kidney disease (CKD).

The research behind renal diets is solid. In a randomized, double-blinded trial of 38 dogs with kidney disease, dogs fed a renal diet went a median of 615 days before a uremic crisis. A uremic crisis is a sudden buildup of waste in the blood. Dogs on a regular adult food went 252 days.

k/d also has trade-offs. It needs a prescription, its first ingredients are brewers rice and chicken fat, and it costs about $140 for a 27.5 lb bag at 1-800-PetMeds. Some dogs also turn it down. IRIS notes that a kidney diet is easier to start before a dog's appetite fades.

Why k/d needs a prescription

k/d is lower in phosphorus and protein than an everyday food is allowed to be. AAFCO sets minimums for adult dog food of 0.4% phosphorus and 18% protein on a dry-matter basis, as our guide to AAFCO nutrient profiles explains. k/d's 0.29% phosphorus and 15.6% protein both sit below those lines.

Diets like this are made for dogs with a diagnosed disease, so FDA policy expects them to be sold under a veterinarian's direction. A dog with early kidney changes, or a healthy senior, may only need a complete food at the low end of the normal phosphorus range.

When does a dog need a prescription kidney diet?

Most dogs need a prescription kidney diet by stage 3 CKD, or sooner if they have protein in their urine. The IRIS treatment recommendations say to feed a kidney diet from stage 3 and to consider one at stage 2.

Stage 1 and early changes

Stage 1 is different, and many dogs at this stage show no outward signs. Dr. Cailin Heinze, a board-certified veterinary nutritionist, writes in dvm360 that early CKD without proteinuria (protein leaking into the urine) can start with lower phosphorus alone.

In that case, she says some regular foods can be considered if they stay under 1.5 g of phosphorus per 1,000 kcal, which is 150 mg per 100 kcal. She notes that only a handful of foods meet that line.

When to stay with k/d

• Stage 2 to 4 CKD: IRIS recommends considering a renal diet at stage 2 and feeding one from stage 3, with phosphorus tracked against set targets.
• Protein in the urine: dogs losing protein through their kidneys usually need the protein restriction a renal diet provides.
• A dog doing well on k/d: if your dog eats it happily and the bloodwork is stable, there is no reason to change.

Where the Whole Food Mixer fits

The Whole Food Mixer is a complete and balanced food for adult dogs. You add water to serve it, and it works as the whole meal. In third-party lab testing it measured 0.41% phosphorus as fed, or about 117 mg per 100 kcal.

That keeps it within AAFCO's normal range for adult food, at 0.45% on a dry-matter basis, and under the 150 mg line Dr. Heinze describes for early kidney disease. Plant proteins help make that possible. Dr. Heinze writes that "most meats are high in phosphorus," so a food's animal protein often limits how low its phosphorus can go.

The Mixer is the lowest-phosphorus recipe Petaluma makes. It is a premium food made from whole-food ingredients like organic soy, pumpkin, and spinach, and it contains no animal ingredients.

Dogs it can suit

• Early kidney changes: a dog at IRIS stage 1 with no protein in the urine, when your vet agrees a non-prescription food is reasonable for now.
• Healthy seniors: older dogs with normal kidney values whose owners want a lower-phosphorus everyday food.
• Dogs who prefer a fresh-style meal: the Mixer is dehydrated whole food served with water, a softer texture than kibble.

The Mixer is not a renal diet. Its protein is not restricted, at 26.8% on a dry-matter basis, and it has not been studied as a kidney treatment. For a dog that has moved past stage 1, k/d or another prescription renal diet is the better choice. Our article on protein for senior dogs explains why healthy older dogs usually need more protein, not less.

If your dog eats a meat-based food now

Most dogs whose owners look for a kidney-friendly food are eating a chicken or beef recipe today. Dogs need specific nutrients, such as essential amino acids, rather than specific ingredients. A complete and balanced plant-based food supplies those nutrients from plants. Our article on whether dogs need meat walks through the research.

Whatever the protein source, phosphorus per 100 kcal is the number to compare when kidneys are the concern. Many labels do not list phosphorus at all, so you may need to ask the brand for it.

Change foods gradually, mixing a little of the new food into the old. A veterinary guide to the IRIS recommendations advises switching kidney patients over several weeks, and our transition guide has a step-by-step schedule. A sample of the Mixer lets you see whether your dog likes it before you buy a full bag.

If your senior's kidney values are normal, our Baked Pumpkin & Peanut Butter Flavor for Senior Dogs is another option. It has more phosphorus than the Mixer, at about 0.73% as fed in lab testing, so the Mixer stays the better pick once kidney values start to rise.

Hill's k/d vs. the Whole Food Mixer, side by side

The two foods are built for different jobs. k/d restricts phosphorus and protein for a diagnosed disease, and the Mixer is a low-phosphorus everyday food for dogs who are not there yet.

Hill's figures are from the k/d product page; its phosphorus per 100 kcal is the most it can be, given 0.29% on a dry-matter basis and 3,991 kcal per kg. Petaluma's figures are from the third-party lab analysis linked on the product page. Prices were checked in November 2026 and change often.

Per calorie, k/d costs less than the Mixer. The Mixer is a premium whole-food recipe you can buy without a prescription.

Questions to ask your vet before switching

The best decision comes from your dog's own bloodwork. These questions help you get a clear answer at the next visit.

• What IRIS stage is my dog? Stage 1 and stage 2 call for different diets.
• Is there protein in the urine? Ask for the urine protein-to-creatinine ratio (UPC). IRIS calls for a closer look at any UPC above 0.5.
• What phosphorus level should the food stay under? Bring the Mixer's 117 mg per 100 kcal so your vet can compare.
• When should we recheck? Early kidney changes can move slowly or quickly, so agree on a schedule for repeat bloodwork and urine tests.

If you and your vet decide to switch, go slowly, over several weeks, as described in the section on switching above. Our article on managing CKD in dogs covers the rest of a kidney care routine.

Frequently asked questions

Is there a non-prescription alternative to Hill's k/d?

For dogs with stage 3 kidney disease or later, or protein in the urine, a prescription renal diet is the standard choice. The IRIS treatment recommendations also suggest considering one at stage 2. For very early changes without protein in the urine, a board-certified veterinary nutritionist says some regular foods can work. They need to stay under 150 mg of phosphorus per 100 kcal. Petaluma's Whole Food Mixer measured 117 mg in lab testing.

Can I switch my dog from k/d to a non-prescription food?

Only with your vet's guidance. A dog on k/d for diagnosed kidney disease is getting deliberate phosphorus and protein restriction, and any regular food, plant-based or not, contains more of both. If your vet confirms your dog's kidney values are in the early range, ask whether a low-phosphorus complete food fits.

Is a plant-based food safe for a dog that has always eaten meat?

Yes, when the food is complete and balanced for adult dogs. Dogs need nutrients rather than specific ingredients, and a complete plant-based food supplies them. Our article on whether dogs need meat covers the research. Switch gradually, and see our transition guide for a schedule.

Why does Hill's k/d need a prescription?

k/d's phosphorus and protein sit below the minimums AAFCO sets for everyday adult dog food, so it is meant for dogs with a diagnosed disease. FDA policy expects diets like this to be sold under a veterinarian's direction. 1-800-PetMeds, for example, contacts your vet to approve the order before it ships.

Does a kidney diet help dogs live longer?

The evidence says yes for dogs with established kidney disease. In a randomized, double-blinded trial of 38 dogs, dogs on a renal diet went a median of 615 days before a uremic crisis. Dogs on a regular adult food went 252 days.

How much phosphorus is in the Whole Food Mixer?

In lab testing, the Whole Food Mixer measured 0.41% phosphorus as fed, or about 117 mg per 100 kcal. That is the lowest of Petaluma's three recipes and below the 150 mg level that Dr. Cailin Heinze uses as the cutoff for regular foods in early kidney disease.

Is plant-based food good for dogs with kidney disease?

A complete plant-based food can be a good fit for some dogs with early kidney changes, as long as its phosphorus is low. The number on the label matters more than the protein source. Our guide to diet and kidney disease covers how Petaluma's recipes compare.

References

1. Jacob F, Polzin DJ, Osborne CA, et al. Clinical evaluation of dietary modification for treatment of spontaneous chronic renal failure in dogs. Journal of the American Veterinary Medical Association. 2002;220(8):1163-1170. PubMed.
2. Heinze CR. Renal diets for veterinary patients: What to feed and when to start. dvm360. 2016, updated 2020. dvm360.
3. Grauer GF. Treatment guidelines for chronic kidney disease in dogs and cats: International Renal Interest Society recommendations. Today's Veterinary Practice. 2017. Article.
4. International Renal Interest Society. IRIS treatment recommendations for CKD in dogs. May 2026. iris-kidney.com.
5. Hill's Pet Nutrition. Prescription Diet k/d Kidney Care with Chicken dry dog food. Accessed November 2026. hillspet.com.
6. U.S. Food and Drug Administration. CPG Sec. 690.150: Labeling and marketing of dog and cat food diets intended to diagnose, cure, mitigate, treat, or prevent diseases. 2016. fda.gov.
7. 1-800-PetMeds. Hill's Science Diet Adult Chicken & Barley dry dog food, 15 lb. Accessed November 2026. 1800petmeds.com.
8. 1-800-PetMeds. Hill's Prescription Diet k/d Kidney Care with Chicken, 27.5 lb. Accessed November 2026. 1800petmeds.com.