Can Kittens Eat Adult Cat Food?

Protein is essential to any cat's diet as it is the building block for organs and tissue, including cartilage, skin, hair, and blood. Proteins are made up of amino acids, many of which cats cannot produce.  

As obligate carnivores, cats have adapted to source these amino acids from animal protein, which is why it’s a staple in their diet. Cats also use protein for energy when possible, requiring more than omnivores like dogs.  

Kittens need a minimum of 30% protein in their diets to support their rapid growth and development, although some commercial kitten foods, such as the Wellness® Core® Kitten Food, go as high as 45% protein. However, the minimum protein requirement for adult cats is 26% protein, as they’re no longer growing.  

The protein in kitten food is essential for fueling their bodies' natural processes, such as building muscle, developing tissues, and supporting their immune system. Without the appropriate high-quality protein, kittens can face several health problems, including stunted growth, muscle loss, lethargy or fatigue, and a weakened immune system.  

In addition to protein, kittens also need a higher fat content in their food than adult cats to support their growth. Not only is the fat in kitten foods very energy-dense to help fuel their active little bodies, but it is also essential for digesting fat-soluble vitamins, including Vitamin A, D, E, and K, which are needed to support various bodily functions.

Animal fats also help your cat’s body break down protein from food into glucose. They are a great source of omega-3 fatty acids essential for a kitten's brain and eye development, and support their skin and coat health.  

As mentioned, kittens need a significantly higher fat content in their food. The minimum fat requirement for adult cat foods is 9%. Kitten foods, however, tend to contain between 14% and 35% fat, like the Hill's™ SCIENCE PLAN™ Kitten food with 23.5% fat content, which contributes to optimal health.  

Along with protein and fats, cats and kittens also need a range of vitamins and minerals to help keep their bodies working optimally. While the vitamins cats and kittens need tend to be the same, kittens need substantially more of them, not just to manage their health, but also to aid in the development of various bodily functions.  

For example, kittens need much more phosphorus (1.8g), calcium (2.0g), and sodium (350mg) than adult cats to support their growth, bones, and teeth. Since adult cats don’t need as many minerals, kittens fed only adult food may suffer from mineral deficiencies, which can cause stunted growth, joint and bone problems, and skin issues.  

Finding the right balance of vitamins and minerals is essential to ensure your cat's health, as too much of certain minerals or vitamins can be as bad as too little. For example, adult cats need more chloride and potassium in their diet to manage blood acid levels and regulate nerve impulses and heart function. However, too much potassium or chloride can cause muscle weakness and arrhythmias in kittens.  

To avoid mineral deficiencies, choose an appropriate kitten food that includes a balance of the vitamins and minerals they need.  

Changing your cat’s food too quickly can cause digestive issues, or your cat may reject the new food because they’re happy with the food they’re eating. You should gradually transition your kitten to adult food over 7-14 days.  

 Here’s our quick guide to switching kitten food to adult food:  

• Day 1-2: Give your cat their meal as ¾ of their old food and ¼ of their new food.  
• Day 3-4: Give your cat a meal of ½ their old food and ½ new food. 
• Days 5-7: Give your cat a meal of ¼ of their old food and ¾ of their new food. 
• Days 8-10: Only give your cat their new food.  

If your cat is fussy or refuses to eat their new food, then go back to a stage they’ll eat and give them some more time before adding more adult food. Some cats prefer to eat kitten food, so transitioning them may take longer. If you’re changing dry foods, mix the new and old biscuits or choose the adult version of your kitten’s current food to ease the transition. If you’re switching between wet foods, try having the different foods in separate bowls.