Due to many metabolic and immunologic functions, the liver is one of the most important organs, both in animals and the human body. Every liver disease leads to the dysfunction of the whole organism. Therefore, early recognition of the disease and the start of the therapy is crucial. A customized diet is a very big part of the therapy when it comes to liver diseases. Although most liver diseases have very similar or/ and same symptoms, the pathophysiology that caused them is very different. Due to that fact, before starting any new diet, we must be sure of what disease we are talking about. The most common diseases we see in everyday practice, are the following: portosystemic shunt, copper storage disease, hepatitis contagiosa canis, and cirrhosis hepatitis. In every diet plan, we make for these diseases, the main goal will be protein reduction. However, some other factors must be taken into consideration, like how old is the animal, its level of activity, and possibly some other diseases that the patient deals with. Due to that, the exact amount of protein and the sources of the protein will be different for every patient, as well as the medicines and nutraceuticals. For treating liver diseases, the owners must know their role in this whole process. Therefore, we must explain to the owners what nutrition options they have. Whatever they choose (commercial veterinary diet option or individually formulated homemade diet option), the most important thing is that their pets' food is well balanced and gives their pets all the important nutrition they need without burdening already dysfunctional liver.