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The Mysterious Feline Life Stages: When Is a Kitten a Cat?

Analysis by Dr. Karen Shaw Becker

ginger cat

Story at-a-glance -

  • Many pet parents aren’t sure when, exactly, their no-longer-a-kitten is considered a fully-grown cat
  • During the first 6 weeks of life, a kitten’s growth and development is “turbo-charged”; the kitten stage is followed by several other feline life stages (junior, prime, mature and more)
  • At around age 11, cats move into their senior years
  • Kitties 15 years and older are considered geriatric
  • Well cared-for cats today are living into their 20s; there are many things pet parents can do to provide their kitties with a healthy, happy lifelong lifestyle

If you're wondering when your still-rambunctious kitten will be fully grown, needless to say, the transition isn't as easy to spot in felines as it is in humans. Generally speaking, 18 is the age at which teenagers are considered to be adults, whereas levels of maturity are measured differently in kitties.

During the First 6 Weeks, Kittens Develop at Warp Speed

Weeks 1 through 6 are the period during which kittens grow and develop very rapidly. Since they're all a little different, some may progress a bit more slowly, while others develop more quickly than average. There's no need for concern unless the rate of your kitten's development is significantly different from the norm.

Stage 1: Newborn — Kittens weigh only a few ounces at birth, but they grow very fast, with most doubling their weight in the first week of life. During this time, the mother cat knows she must keep her babies warm, nourish them, and stimulate (lick) their bodies to encourage digestion and elimination.

Newborn kittens can't move around much, and the only noise they make is a faint mew. What remains of the umbilical cord typically drops off on day 2 or 3. They can neither see nor hear, since they're born with their eyes sealed shut and their ears folded. They're also toothless. At some point between days 5 and 14, kitty's little ears will start to unfold and her eyes (always blue at first) begin to open.

Stage 2: Two-week old kitten — At 2 weeks, kittens begin to develop a sense of smell and their eyes open completely, though their vision is still blurry and sensitive to bright lights. At this stage, kittens become aware of their littermates and begin to compete for mom's nipples at mealtime.

Stage 3: Three-week old kitten — During his third week of life, kitty's sense of smell is fully established, and his ears become erect, though his hearing is still developing. He may start to get his little purr on, and baby teeth will begin to push up through his gums. His adult teeth will begin to replace them in a few months. Brief, gentle handling should begin at this point.

At this stage, mama cat no longer needs to stimulate her kittens to help them digest food or eliminate, but she does still have most of the grooming chores.

Stage 4: Four-week old kitten — At 4 weeks, kittens begin to interact with their littermates and show interest in their surroundings. They may attempt a few wobbly steps. By the end of the week, they're typically exploring and playing when they're not napping or nursing.

Stage 5: Five-week old kitten — By 5 weeks of age, kitty's vision is fully developed, and her eye color may begin to change. She's growing more adventurous. Walking is less challenging and pouncing on littermates becomes great fun. This is exactly the right time to begin actively socializing her and getting her used to human handling.

You can also introduce her to solid food this week, but she'll still need to nurse and isn't quite ready to be weaned. This is also a good time to introduce her to her litterbox. I recommend starting with a shallow box lid that she can easily step into and out of, with just a few inches of litter.

Click here to find out Dr. Becker's top tips against seasonal pet allergiesClick here to find out Dr. Becker's top tips against seasonal pet allergies

Feline Life Stage Chart

Like most animals, cats advance through kittenhood and the teen years much faster than humans. A 6-month-old cat is the equivalent of a 10-year-old child, and a 2-year-old kitty is about 24 in human years. At around 5 or 6, the pace slows down a bit, so a 10-year-old cat is approximately 56 in human years.

The following chart shows the life stages associated with feline ages and their approximate human equivalents:1

Life Stage Cat Age Human Equivalent

(Birth to 6 months)

0 – 1 month
2 – 3 months
4 months
6 months

0 – 1 year
2 – 4 years
6 – 8 years
10 years

(7 months to 2 years)

7 months
12 months
18 months
2 years

12 years
15 years
21 years
24 years

(3 to 6 years)



(7 to 10 years)



(11 to 14 years)



15+ years



It's not uncommon for well cared-for cats to live into their late teens and early 20s these days. Unlike purebred dogs, the majority of kitties haven't been selectively bred, which dilutes the inherited traits that cause genetic disease. Indeed, most diseases seen in cats today are lifestyle-related, which means that as your kitty's guardian, you have a great deal of control over how well and how long she lives.

Consulting with a proactive, integrative veterinarian throughout your cat's life affords your kitty the benefit of ongoing and dynamically changing wellness protocols at every phase your cat's life. Supporting your cat physically, metabolically, nutritionally and immunologically as she ages is one the most important things you can do to not only extend lifespan but keep your cat's health exceptional as time goes on.

The Golden Years: Winding Down

There's no need to panic when your feline companion enters retirement, but it is time to start taking steps to ensure she stays as happy and healthy as possible throughout her senior and geriatric years.

Let's take a look at how cats show signs of aging and what you can expect along the way.

From mature to officially a senior (around age 11) — This is a time when most cats begin to slow down a bit. However, it's important to note that just like us, cats are individuals and age at different rates, so there can be signs of slowing down in kitties as young as 8, as well as 14-year-olds who still run around like kittens.

Whatever their age, indoor cats appreciate a consistent daily routine, and older kitties in particular can get very stressed when they encounter something new or different in their environment. Another subtle change you may notice is that your kitty doesn't always greet you at the door when you come home as she once did. She may be playing less and sleeping more.

Many cats also tend to become more talkative as they get older, and more easily startled by strange or loud noises.

Aging kitties often begin to develop many of the same health conditions older humans do, such as arthritis, kidney problems, thyroid disease, or diabetes. That's why I encourage every pet parent with a cat (or dog) over age 7 to schedule twice-yearly veterinary wellness visits; addressing mild kidney disease that has just commenced is much more successful than allowing organ degeneration to occur for twelve months or more before diagnosing it.

Moving beyond the senior stage — By the time your cat is in the 12 to 14-year range, there's a chance he's moving more slowly, and he may be experiencing some loss of vision and hearing. He may also have less tolerance for cold weather. Many older cats develop age-related cognitive decline, so making even small changes in their environment or routine can be stressful for them.

Along with more napping, your senior kitty may become more easily irritated. You may also notice he prefers to spend more time alone. If this is the case, you can increase his feelings of safety and security by making his favorite hideout a warm, comfy little spot he can retreat to whenever he likes.

However, it's also important to remember that older cats still need to interact with their humans regularly, so set aside some time each day to spend with him. Keeping senior cats active is important for muscle tone maintenance and provides cognitive enrichment.

Veterinary checkups will now involve a detailed nutrition and supplement review, senior workup, including a physical exam and blood, urine, and stool sample tests. The results of these tests will provide a snapshot of how well your cat's organs are functioning and point to any potential problems.

Your vet will also check your cat's weight, joint range of motion and blood pressure. I recommend indoor cats be titered in place of automatic vaccines; this is especially important for older kitties.

Age 15 and beyond — Once your kitty reaches 15 years of age, she officially joins the geriatric set, even if it's not all that noticeable yet. She's moving and thinking more slowly now, and she may have one or more age-related health challenges.

She's probably not as alert or responsive as she once was, at times she may seem confused, is sleeping more, perhaps vocalizing more, and interacting with family members less. She may not be as well-groomed as she once was and may occasionally "miss" her litterbox.

As long as your cat is seeing the vet at least twice a year for checkups, and between visits you're keeping a careful eye out for significant or sudden behavior or health changes, there's no reason to be alarmed with your cat "switching gears."

Make every effort to keep her life stress-free by maintaining a consistent daily routine and providing her with her own quiet, cozy spot outfitted with comfortable bedding and a familiar toy or two. Your geriatric cat will appreciate quiet nap zones that include areas of natural sunlight, no EMFs or air pollutants (no second hand smoke, plug-ins, room sprays or candles).

At your regular veterinary wellness visits, you'll want to mention any changes you've noticed in your cat, for example, increased or decreased appetite or water consumption, vomiting, constipation or incontinence, aggressive behavior, or mental confusion.

You'll also want to keep a careful eye out for signs your cat is in pain, which can include hiding, teeth grinding, panting, shortness of breath, loss of interest in food, or reluctance to move around.

All cat parents want their feline family members around for as long as possible, and we also want their lives with us to be happy and healthy. If you're hoping to help your own cat live into her late teens or early 20s, there are many things you can do to provide her with a lifelong lifestyle that offers her the best chance to grow old with you: 8 Tips to Help Your Cat Enjoy a Long, High-Quality Life.

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