The scores
Hill’s Prescription Diet k/d Cat: B (76/100)
Hill’s Science Diet Cat: C (60/100)
A 16-point gap that crosses the grade boundary. k/d earns B status through therapeutic supplements and a cleaner supporting ingredient list.
How the ingredients compare
k/d Cat: Chicken, Brown Rice, Corn Protein Meal, Chicken Fat, Brewers Rice
Science Diet Cat: Chicken, Whole Grain Wheat, Corn Gluten Meal, Chicken Fat, Corn Protein Meal
Both lead with chicken. k/d uses brown rice at two (gentler on the system); Science Diet uses whole grain wheat. Both include corn protein meal and chicken fat, but k/d adds fish oil, FOS, pea protein, egg product, and L-Arginine that Science Diet lacks entirely.
Where Hill’s Prescription Diet k/d pulls ahead
Fish oil provides EPA/DHA omega-3s that research shows may slow kidney disease progression in cats. FOS prebiotics support the gut microbiome, which is increasingly linked to kidney health. Pea protein and egg product provide controlled, high-quality protein sources. L-Arginine is critical for cats — deficiency can be fatal. Betaine supports kidney function. Whole grain oats add soluble fiber. The therapeutic ingredient additions are substantive and well-targeted. Shop on Amazon →
Where Hill’s Science Diet holds its own
Science Diet provides more total protein, which is appropriate for healthy cats that need higher protein levels. It costs less and doesn’t require a veterinary prescription. Whole grain wheat, while not ideal for cats, provides more fiber than brown rice. For cats without kidney disease, Science Diet’s higher protein content is actually a nutritional advantage — k/d’s protein restriction could be harmful for healthy cats over time. Shop on Amazon →
The bottom line
Hill’s Prescription Diet k/d Cat (B/76) wins on ingredient quality over Science Diet Cat (C/60). But CKD is a serious diagnosis, and k/d is a medical diet. If your vet diagnosed kidney disease, k/d is a solid choice with genuinely useful supplements. For healthy cats wanting better ingredients than Science Diet, Wellness Cat (B/80) or Blue Buffalo Cat (B/76) deliver better quality without protein restriction.