What’s actually in Hill’s Prescription Diet i/d?
We analyzed Hill’s Prescription Diet i/d Digestive Care Chicken Flavor dry dog food. The formula leads with chicken — actual whole chicken, not chicken meal — which immediately separates it from the standard Science Diet line. But positions 2 through 6 are all grain or corn-derived: cracked pearled barley, brown rice, brewers rice, whole grain corn, and corn protein meal.
This is a veterinary prescription diet, meaning it’s designed to be purchased through a vet clinic or with a vet’s authorization. The formula is optimized for digestibility in dogs with gastrointestinal issues — the grain selection reflects that medical purpose. Highly processed grains like brewers rice are chosen specifically because they’re easy to digest, not because they’re nutritionally optimal. Shop on Amazon →
The good stuff
Chicken as the first ingredient is a meaningful win. Whole chicken provides high-quality, highly digestible protein — exactly what a dog with GI issues needs. Chicken meal at position eight adds concentrated protein. The formula also includes egg product, flaxseed, and fish oil for omega-3 fatty acids, and pressed cranberries for antioxidants.
The digestibility engineering is genuinely well thought out. The specific grains chosen (barley, brown rice, brewers rice) are selected for their digestive gentleness, and lactic acid supports a healthy gut pH. This is a formula where the grain choices serve a medical purpose, not just a cost-cutting one. Mixed tocopherols provide natural preservation.
The not-so-good stuff
Whole grain corn at position five and corn protein meal at position six represent two forms of corn in the top six ingredients. Corn protein meal is an industrial extract used to boost protein numbers on the label — it’s cheap and nutritionally inferior to animal protein. For a diet that costs $80–100+ per bag, corn-derived protein filler is a hard sell.
Ground pecan shells is an unusual ingredient — it’s an insoluble fiber source used for stool firmness, but it’s essentially ground nut shells with zero nutritional value. Chicken liver flavor and pork liver flavor are palatability enhancers, suggesting the base formula isn’t appealing enough on its own. No probiotics in a digestive care diet is a notable omission — many competitors include them. No chelated minerals.
How it compares
At B/78, Hill’s Prescription Diet i/d scores 17 points higher than the standard Hill’s Science Diet (C/61) — the largest gap in the Hill’s catalog. The upgrade comes from whole chicken first plus a digestibility-engineered grain profile. It now matches mainstream premium brands like Blue Buffalo (B/78) on score, though it still trails top-tier options like Nulo (A/90) and Wellness CORE (A/90) on protein quality and supplement depth.
See the full Hill’s Prescription Diet vs Hill’s Science Diet comparison for a detailed side-by-side breakdown.
i/d is the highest-scoring Hill’s Prescription Diet formula we’ve analyzed. k/d Kidney Care (B/76), j/d Joint Care (B/76), z/d Skin/Food Sensitivities (B/76), and w/d Multi-Benefit (B/76) all trail i/d by 2 points, while Metabolic (C/58) scores substantially lower.
This comparison comes with a caveat: Prescription Diet i/d exists for dogs with diagnosed digestive conditions. Ingredient quality scores don’t capture the therapeutic value of a formula designed to manage IBD, colitis, or post-surgical recovery. Your vet prescribed this food for a medical reason — that context matters more than the ingredient grade.
The bottom line
Hill’s Prescription Diet i/d earns a B grade (78/100) from KibbleIQ — the highest score in the entire Hill’s Prescription Diet lineup. The ingredient quality is solid, with whole chicken first and a digestibility profile engineered for GI recovery. The corn and grain content is still heavier than non-prescription premium brands, but in a therapeutic context that engineering is deliberate. If your vet prescribed i/d for a specific digestive condition, follow their guidance — the medical formulation serves a purpose that ingredient grades don’t fully capture. If your dog’s digestive issues have resolved and your vet gives the green light to transition, consider upgrading to Nulo or Wellness CORE for a substantial ingredient quality improvement with built-in digestive support from probiotics. Shop on Amazon →