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When Does a Kitten Become a Cat? – Everything You Need to Know About Kitten Development

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Fact checked by Dr. Antoinette Martin, DVM

If you have ever owned a kitten before, you have probably noticed how quickly they grow. In fact, by just six months of age, most kittens have already reached puberty and are nearing their full adult size. While you may assume that this rapid growth cycle means kittens become adults as soon as they reach half a year of age, nailing down a specific age is not so simple.

In cats, adulthood is signified by physical milestones rather than reaching a specific age. Since kittens and adult cats have different dietary needs, many cat owners wonder when they can begin treating their kitten as an adult cat, which is why you must know when your cat can be considered an adult.

While many veterinarians subscribe to the belief that a kitten is an adult cat after it has reached one year of age, this is more of a general guideline rather than an exact age where your cat will stop growing and maturing.

How Can We Help?

To help you understand when your kitten will become a cat, we have highlighted some important information about kitten development. We will go over some general age ranges where most cats reach physical milestones that signify the beginning of adulthood.

We will go over the various life stages of a cat and explain when most cats reach their full adult size. We will also explain some of the many factors that determine how quickly your cat will grow.

To help you make sure that your kitten has a healthy transition into adulthood, we will also provide some useful information for how you can prepare your furry friend for a happy and healthy life! If you have questions, talk to a Hello Ralphie vet online today.

adorable kittens playing together outdoor

Stages of Kitten Development

  • 2 Weeks – By this age, most kittens have opened their eyes for the first time.
  • 3 Weeks – The ear canals have fully opened.
  • 4 Weeks – The kitten’s baby teeth have begun poking through the gums. They can also begin exploring their surroundings and are becoming more mobile and curious.
  • 8 – 12 Weeks – By this age, kittens are old enough for their first vaccinations, which means they are now old enough to be separated from their mother, which is why most cats go to their new home at about 12 weeks of age.
  • 4 Months – The kitten’s baby teeth are beginning to fall out and are replaced by adult teeth. In general, a kitten will have a full set of adult teeth by the time it reaches 7 months of age.
  • 5 – 6 Months – Most kittens have now grown enough to be safely spayed or neutered.

By the time your kitten has reached 6 months of age, it has most likely grown close to its full adult size. While their growth may slow down after 6 months, the development and growth phase will usually continue until the cat is roughly one year old, which is why many veterinarians treat the 12-month point as the age when a kitten becomes an adult.

Adult Cat Phases

After a kitten has reached adulthood, they continue to go through life phases, but these occur at a slower rate:

Junior (8 Months to 2 Years):

During this stage, cats will complete their growth cycle and reach their full adult size. During this stage, cats become more confident and are just as playful as they were during their kitten years. Put in the effort to play with your cat during this stage of its development, as mental stimulation is incredibly important.

Prime Adult (2 to 6 Years):

By this age, the cat has been fully grown for some time and is in its prime years.

Mature Adult (6 to 10 Years):

Cats tend to become less active as they age, which is why owners must pay extra attention to their cat’s diet and exercise. Mature cats are more susceptible to unhealthy weight gain, which can cause them to develop serious health issues, like diabetes and kidney issues.

Senior (10 to 14 Years):

Senior cats are much less mobile, and it is typically the phase where the cat’s health has begun to deteriorate. Vet appointments should become more frequent, and you should strictly control the cat’s diet.

senior domestic cat isolated on white background

Factors That Influence Growth Rate

Many factors will determine how quickly your kitten will reach its full adult size. Genetics plays a major role, which is why knowing your cat’s breed will help you guess when it will stop growing. Larger breeds take longer to reach their full size, while smaller breeds reach physical maturity much faster.

Diet will also play a role. Since kittens have specific caloric and nutritional needs as they grow, those that are fed appropriate and healthy diets will reach their adult size faster. Those that do not receive a proper diet can suffer from stunted and slowed growth.

The age when the cat is spayed or neutered will also impact its growth rate, which is why you should always listen to what your veterinarian recommends in regards to the age when your cat should be spayed or neutered. One of our online vet appointments can be one of the easiest ways to come up with a plan for your particular cat.

When Should You Switch from Kitten Food to Adult Food?

Since there is no magic age when cats become adults, knowing when to switch your kitten to adult food can be somewhat tricky. For most cats, somewhere in the range of 9 to 12 months of age should be appropriate; however, the decision should be based on more than just age.

One of the easiest ways to make sure your kitten is ready for the switch is to speak with an online vet. An online veterinarian will be able to assess your cat and let you know when you can make the transition to adult food. Best of all, the appointment can take place from the comfort of your own home, which means your young cat will not have to experience the stress and anxiety that goes with taking it to an in-person clinic.

What Can You Do to Make Sure Your Kitten is Healthy?

If you want to make sure that your feline friend has everything it needs to develop happily and healthily, there are plenty of resources out there that can help. For starters, you can speak with a vet at Hello Ralphie to answer any questions you may have about cat ownership and kitten development. Book an online vet appointment today, and a virtual vet will be happy to help you set your cat up for a healthy life!

In addition to a visit with a virtual veterinarian, the following online resources can also be incredibly beneficial, especially for new cat owners:

How Often Should You Change Cat Litter

Cat Enrichment Solved

Why is My Cat Overgrooming

How do I Brush My Cat’s Teeth?

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