Editorial · PetScored desk · May 15, 2026

Why prescription diets only score in the sixes.

Your vet handed you an $80 bag of Hill’s k/d, you looked it up here, and the score came back 6.8. If your first thought was that one of us must be wrong, you are reading it the way most people do. Here is the part that resolves it: both can be right at once. Across the ten prescription diets we score, the average is 6.5, against an all-brands average of 7.0. That number is not a knock on the food. It is the rubric telling you something real about how these formulas are built.

By the PetScored Editorial Team. Reading time: 5 minutes.

What you are actually holding

A “prescription diet,” sometimes called a therapeutic diet, is a food your vet sends you home with for a dog who has a diagnosed condition: kidney disease, pancreatitis, food allergy, obesity, hyperthyroidism, urolithiasis (bladder stones), and the like. Worth knowing, since it surprises a lot of people: in the U.S. these foods are not legally required to be prescription-only. That part is a manufacturer-and-channel convention, not a law. What they all share is one clinical constraint that drives the whole recipe.

Take three you may have seen. The k/d formula is built around reduced phosphorus and controlled protein to slow chronic kidney disease. HA Hydrolyzed is built around protein molecules broken below the size that triggers an immune response, so a severely allergic dog, or one on an elimination trial, can eat it without reacting. y/d is built around severe iodine restriction, a way to manage hyperthyroidism without surgery. In each case the medical goal comes first and the recipe follows from it. Everything else is downstream.

Where each one landed

Here is every prescription diet we score, ranked best to worst. The numbers pull live from our data, so this is the real spread, not a list we tidied up for the article.

Why the score sits where it does

The score blends five sub-scores, and for prescription diets two of them do most of the dragging. One is Ingredient Clarity, where we reward a short, named, recognizable ingredient panel. The other is Value, where we compare what a food costs per 1000 calories against the typical price for its category. Across these ten, the average Ingredient Clarity comes out to 4.9. So you know it is not the brands losing the points: their average Brand Trust is 6.4, the highest tier we hand out, because these are the same three brand families we covered in last week’s vet-channel editorial.

The clarity hit is baked into the recipe, not a sign of a corner cut. A renal diet swaps egg product, corn starch, and refined fats in for first-ingredient muscle meat precisely because muscle meat is high in phosphorus, the thing it is trying to limit. A hydrolyzed-protein diet leans on hydrolyzed soy instead of intact animal protein because intact animal protein is exactly what the allergic dog’s immune system is reacting to. A high-fiber weight-loss diet leads with powdered cellulose because the point is to fill the dog up on very few calories. Read on a normal ingredient panel, those choices look like compromises. They are the formula doing its job.

What our score can and cannot tell you

Here is the line, because it matters for how you read that 6.8. We grade what the label can prove: nutrient density against AAFCO benchmarks, how specific the ingredients are, how transparent the brand is, how much exposure there is to common sensitivity triggers, and cost per calorie. What we do not grade is therapeutic efficacy, whether the food actually works on the condition. A renal diet that genuinely slows kidney disease is doing the one thing the bag was made to do, and that win never shows up on our scorecard. We do not score whether a food is treating the disease, full stop.

You will find this spelled out under what we refuse to score: we will not tell you that a specific food treats or cures a specific condition. Saying that would take clinical evidence we do not have, and it is the call of a vet who has examined your dog, not a rating site. We report what we can measure and stay quiet about what we can’t.

If your vet put your dog on one of these

The most important thing we can tell you: please do not switch off a prescribed diet because of a score on a rating site, ours or anyone else’s. Your vet is working from things we will never see, the bloodwork, the urinalysis, the biopsy, how your dog did on past foods, and the food is one piece of a treatment plan built around all of it. If the score has you worried, the conversation to have is with the vet, not with us.

And the reassuring read, since the number probably rattled you: a 6.8 is not a bad score. The all-brands average is around 7.0, and prescription diets sit right at or a little above that. The points they give up are on ingredient elegance and price, the exact two things a therapeutic formula trades away on purpose to do its job.

The one thing that would move these scores

If you are wondering whether these scores could ever climb, there is one change that would lift them without touching the clinical design: clearer published evidence that the specific recipe was tested in a feeding trial for its target condition. Most prescription diets carry the weaker AAFCO “formulated to meet” adequacy statement rather than the stronger “Animal feeding tests using AAFCO procedures” one. The careful safety work behind these formulas is real; putting more of it on paper would add about half a point to Brand Trust. We hope the manufacturers publish more of it over time.

- The PetScored desk. Holding one of these bags right now? Click any product above to see exactly how that recipe was scored, line by line.