Prescription Diets and veterinarian recommendations
It is not unusual for your vet recommend a specific food or type of food based on their diagnosis of your pet. They understand that proper nutrition can often complement other medical therapies when addressing health issues.
Some of these recommendations may steer you towards prescription diets. The prescription foods from Iams, Royal Canin, Hills, Purina and Waltham are formulated to address a specific medical issue. There are not always commercial alternatives to some these formulas.
Some prescription diets do have commercial equivalents which may address the same issue with a better quality formulation. Formulas for weight control, food sensitivities or joint support all fall into this category.
If your vet has suggested a prescription food in the above cases, ask if an alternative would be acceptable. Often it is easier, and more profitable, for a vet to initially recommend the prescription foods sold in the clinic. Whether that is the proper choice, or only one option to consider, is a subject to be explored.