How Long Should Cats Eat Kitten Food?

If you are the pet parent of a kitten and you’re wondering when you are supposed to switch to an adult cat diet, it’s a good thing you’ve ended up here. 

I’m a former veterinarian and I’ll explain in this article the basics of cat ages and the nutrients requirement of kittens, adults, and geriatric cats. The short answer to the question, however, is until they reach 12 to 18 months of age. 

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A bit about cat ages


It’s generally acknowledged that kittens become adults when they reach 1 year of age. 

But the issue is a little more complicated than that. For example, some breeds grow up slower, such as the Maine Coon, which is estimated to reach adulthood around 18 months of age. 

Between the ages of 1 and 7, your cat will be considered an adult. Once he or she gets older than 7, your pet can be considered a senior and needs to be given an appropriate diet. 

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What nutrients does a kitten need?

Cats are carnivores no matter their age, so even kittens need more protein than the young ones of other species. The essential nutrients in a kitten’s diet are the following:

  • Protein
  • Fat
  • Calcium

Calcium is important because the bones of the kitten are still growing. Kittens have the highest protein requirement when they are weaning. Fat is important for a number of organs and tissues, especially the nervous system. 

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Around 30% of their diet needs to be composed of protein coming from high-quality kitten food (after weaning). Treats aren’t that important, and they should make up about 5% of the entire diet. 

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What nutrients do adult cats need?

50% of an adult cat’s diet needs to be composed of protein. Less than 10% should come from carbs, and around 30% of a cat’s daily diet should come from fat sources. 

Not all fats are the same, just like not all protein sources or carbs are made equal. As previously mentioned, cats should primarily eat protein (because that’s what they consume in the wild). 

So feeding your adult cat a diet that contains carbs coming from corn or wheat is not a good idea and can lead to a lot of health complications. 

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What nutrients to geriatric cats need?

Senior cats have similar dietary needs to adult cats. However, they should receive plenty of water and antioxidants, and in some cases, they might have to be fed less protein. 

This is especially true in cases where the geriatric cat suffers from a urinary pathology. 

It’s not uncommon for senior pets to develop kidney disease or have various skin problems, so they need to be taken to the vet more often (3 times a year), and they usually have to be prescribed a specific diet. 

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Can you feed kitten food to adult cats?

It depends. If you have a kitten and an adult cat living in the same household and you’ve run out of food for the second, you can definitely give her some canned food or kibble made for kittens. 

But I wouldn’t recommend doing this for more than a couple of days, until you get more supplies. As previously discussed, adult cats have different nutritional requirements compared to kittens. 

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While the kitten food is not necessarily going to make them sick for a short amount of time, it could cause problems in the long run. 

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How is kitten food different from adult cat food?

In short, it has more calcium and it’s also richer in calories (and it contains more fat). That’s why kittens shouldn’t eat adult cat food as it definitely does not satisfy their nutritional needs. 

Kittens that are fed an adult cat food diet can become malnourished and can even end up suffering from rickets.

Feeding your adult cat a kitten diet for months on end can make her fat, to name a complication.  

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How to transition your kitten to adult cat food

The best way to switch your kitten to food for adults would be to gradually mix it into the kitten food. Even if you choose the same brand, you might notice that cats don’t really like sudden changes, so using this method is the best way of going about things. 

Feed your kitten 25% adult cat food and 75% kitten food for several days, then increase the amount of adult food to 50%, then 75%, and then completely. 

This post contains affiliate links on some of the images. You can support this blog by trying out the products recommended in this article. 

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Cristina Vulpe is a licensed veterinarian who has been a cat owner since she was 12. She is passionate about giving useful advice to pet owners across the world. Her favorite topics range from pathology and novel therapies to infectious diseases and animal welfare. Her work has been featured in many online publications from The Pet Friendly House to Alpha Paw, Animal Wellness Magazine, and Currently, she is a Pet Content Specialist for IkoBrands.

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