The Royal Canin Veterinary Diet Feline Renal Support A Dry Cat Food, requires a prescription and is ideal for kidney-related issues. The best low-protein cat foods are carefully formulated by veterinarians rather than cat food companies, but cost more than nonprescription foods. Dry foods are the most common, as they have a longer shelf life and are often cheaper than other food types. Wet foods have two major downsides: their high moisture content is good for weakened kidneys, and cats tend to reject wet food less often than dry food. Raw foods are another lesser-used option. Depending on the type of cat food used, cats can prefer poultry or fish. The cost of the food depends on how much it is purchased.