Veterinary Diets: When are they needed and how do they work?

If your veterinarian has told you that your dog or cat needs a "special diet" or "veterinary food," it's normal to have questions. What makes this food different? Why is it more expensive? And is it really necessary to follow it strictly?

In this article, we explain everything you need to know about veterinary foods – what they are, how they work, for what conditions they exist, and what you should consider when using them.

What is a veterinary food?

Veterinary food, also known as a therapeutic diet or clinical diet, is food specifically formulated to help manage or treat certain health conditions in animals. Unlike conventional foods – even premium ones – veterinary foods have very specific nutritional compositions that serve a concrete clinical objective.

This can mean, for example, a very reduced phosphorus content to spare the kidneys, a hydrolyzed protein to minimize allergic reactions, or an adjusted mineral profile to dissolve or prevent urinary stones.

These foods are not "healthier" than a good conventional food for an animal without health problems. They are clinically targeted for those with a specific need.

Do I need a veterinary prescription to buy?

In Portugal, veterinary foods are not subject to mandatory medical prescription in the same way as medicines. However, they are always indicated and monitored by a veterinarian, and it is highly recommended that the choice be made based on the veterinarian's diagnosis.

Using a renal diet on a healthy animal, for example, can cause long-term nutritional imbalances. And using the wrong food on a sick animal may not solve – or even worsen – the problem. Therefore, veterinary supervision is not optional, even if the purchase can be made freely.

For what conditions do veterinary foods exist?

There is quite a wide variety of conditions for which therapeutic diets have been developed. The most common are:

• Kidney problems: Renal foods have reduced phosphorus and protein to decrease the workload on the kidneys. They are among the most used, especially in older cats, who are very prone to chronic kidney disease.
• Urinary problems: Formulated to dissolve struvite or calcium oxalate stones, or to alter urine pH to prevent their formation. Very common in both dogs and cats.
• Gastrointestinal problems: For animals with chronic diarrhea, inflammatory bowel disease, or malabsorption. They have more digestible proteins, lower fat content, and sometimes specific fiber to regulate intestinal transit.
• Allergies and food intolerances: They use hydrolyzed proteins (fragmented into particles so small that the immune system does not recognize them) or "novel" proteins – sources the animal has never eaten before, such as duck, horse, or insects. They reduce immune reactions that cause itching, skin problems, or diarrhea.
• Obesity and weight control: With reduced calories but complete nutrition, they allow weight loss without nutritional deficiencies. Many also have high fiber to increase satiety.
• Diabetes: With a low glycemic index and sometimes high fiber content, they help stabilize blood glucose levels.
• Liver problems: Moderate and high-quality protein to avoid overloading the liver, with antioxidants and support for liver function.
• Heart diseases: With reduced sodium to decrease fluid retention and cardiac effort.
• Joint problems: With high amounts of omega-3 fatty acids (EPA and DHA) to reduce inflammation in the joints. Sometimes combined with glycosaminoglycans like glucosamine and chondroitin.
• Post-surgical recovery or convalescence: Rich in high-quality protein and energy to support healing and muscle recovery.

How do they work in practice?

Most veterinary foods are intended for continuous use as long as the health condition persists. They are not a "cure" – they are nutritional management that, in combination with medical treatment, helps the animal live better and reduce the progression of the disease.

Some can be used temporarily – such as post-surgical recovery or gastrointestinal diets in an acute phase – and then the animal returns to a normal diet.

Others, such as renal, cardiac, or allergy diets, are usually for life, as the conditions they treat are chronic.

An important point: the transition to a veterinary food should be done gradually, mixing the new food with the old over 7 to 10 days. This reduces the risk of gastrointestinal disturbances and helps the animal accept the new food better.

Are they expensive? Is the investment worth it?

Veterinary foods have a higher price per kilogram than conventional foods. This is due to the investment in research, the quality and specificity of the ingredients, and the fact that they are produced in smaller volumes.

However, when compared to the costs of recurrent veterinary treatment, hospitalizations, or continuous medication that may be necessary without adequate feeding, the therapeutic diet often turns out to be an investment that saves money in the long run – in addition to significantly improving the animal's quality of life.

Buying in larger packages (when applicable) significantly reduces the cost per kilogram.

Frequently Asked Questions (FAQs)

Can I give my pet veterinary food without veterinary indication? Technically yes, but it is not recommended. Veterinary foods are formulated for specific conditions and can cause nutritional imbalances if used unnecessarily. Always consult your veterinarian before starting any therapeutic diet.

How long does my pet need to eat veterinary food? It depends on the condition. Some diets are temporary – such as recovery or gastrointestinal diets in an acute phase. Others, such as renal, cardiac, or allergy diets, are generally for life, as they manage chronic conditions.

Can veterinary food be mixed with regular food? During the transition phase (7 to 10 days), yes – gradually. But after the transition, ideally the therapeutic diet should be the only main food, to ensure the animal receives the correct formulation. Snacks and treats should be avoided or chosen carefully.

Why is veterinary food more expensive than regular food? The higher cost is due to investment in clinical research, the quality and specificity of ingredients (such as hydrolyzed proteins or very controlled mineral levels), and production in smaller volumes. Buying larger packages helps reduce the cost per kilogram.

My cat refuses to eat veterinary food. What do I do? It's relatively common, especially in pickier cats. Try to warm the food slightly to intensify the aroma, gradually mix it with the previous food, or try moistening it with a little warm water. If the refusal persists, talk to your veterinarian – sometimes there is an alternative within the same therapeutic line.

Is wet veterinary food as effective as dry? Yes, and in some situations it is even preferable – for example, in renal and urinary diets, the high water content of wet food helps keep the animal hydrated and dilute urine. Many veterinarians recommend a combination of dry and wet.

Can I give veterinary food to other healthy pets living in the same house? It is not recommended. Veterinary foods have very specific compositions that are not suitable for animals without the condition in question. If you have several animals at home and one of them needs a therapeutic diet, talk to your veterinarian about how to manage separate feeding.