Why Is My Full-Grown Cat So Small?

There are many reasons why a full-grown cat may be undersized, including stunted growth and weight loss. By themselves, these causes are usually the symptoms of malnourishment, parasites, or health problems. However, there are cat breeds that are naturally slim and petite, such as munchkin and devon rex breeds. Cats also have sexual dimorphic traits, with males often being larger than females.

A fully grown cat that is unusually small may have been malnourished as a kitten. This can lead to its growth being permanently stunted. Malnourishment can be caused by a lack of food, too much poor-quality food, or illness and parasites. Cats of any age can also lose weight and appear smaller when ill or afflicted with parasites. A cat doesn’t have to be unwell to lose weight.

Its access to food can be restricted by other, more dominant cats in the household. The same is true for the runt of the litter in kittens. Since other cats routinely deny it food, it cannot get enough nutrition. Weight loss will result, as well as other health issues from malnutrition.

Why Is My Cat So Small And Skinny?

It can be worrying to find that your cat appears unusually small. To figure how what’s happened, you first need to decide:

  • Is it because of my cat’s breed? Certain cat breeds are naturally slim, while others are naturally small.
  • Is my cat eating enough? If your cat loses its appetite or is prevented from eating food by other cats, this can lead to it getting much slimmer.
  • Is my cat’s growth stunted? If your cat has suddenly stopped growing in size, despite aging, then it may have been affected by a health issue early in life.
  • Is my cat ill? Illness, parasites, and malnutrition can lead to weight loss or permanently stunt the cat’s growth.

Some of these won’t require your intervention. Instead, you have the pleasure of owning a tiny cat. Others can be fixed, or the damage can at least be halted. In these cases, you should take action.

Is My Cat’s Growth Stunted?

If you believe your cat’s growth has been stunted, it likely happened when the cat was still a kitten. Malnourishment has long-reaching impacts, even if the cat’s diet is corrected later on. This is hard to tell, though, especially if:

  • It appears otherwise healthy.
  • You don’t have access to its littermates for comparison.

It can be quite obvious in a litter when there is one kitten smaller than the others. By comparison, unless you have multiple cats of the same breed, it can go unnoticed if your cat is undersized.

If your cat is a healthy weight and is absent of any symptoms, then being undersized isn’t really an issue. It can live a long and healthy life. You just have a semi-permanent kitten or your very own toy-sized cat.

On the other hand, if it is losing weight or displaying concerning symptoms, it’s wise to consult a vet. Stunted growth is not a harmful issue, but if the factors that caused this are still impacting the cat, it can be dangerous.

Is My Cat A Runt?

Runts are a natural and rather common occurrence in felines. Usually, there is only one runt in a litter, if there is one at all. At times, there can be two. If the mother experiences problems during pregnancy, the entire litter may be born premature or in a weakened state.

There are several theories as to why runts exist. At times, there are birth defects or complications during pregnancy. Others suggest that the embryo’s placement in the womb plays a role in determining the runt of the litter. All told, it’s a game of chance as to whether or not a mother will give birth to a runt.

Unless you can compare your cat’s size to its littermates, it can be difficult to tell if it is a runt. With proper care (and a lack of mortal deformities and complications), runts will grow into healthy cats. They may even grow to a normal adult size, but they have a greater chance of being smaller than average.

If you care for a mother cat and her litter, pay extra attention to the runt if there is one. Sad as it is, she may reject the runt and refuse to nurse or care for it. It’s a survival-of-the-fittest instinct, and she may even kill the kitten to improve the chances for the rest of the litter.

You will need to remove the kitten and provide it with special care, or it will die. Very young kittens need specialized care. According to the University of Wisconsin-Madison, kittens need:

  • An external heat source
  • Hand-feeding
  • Socialization
  • Cleaning
  • Toileting

What Causes A Cat To Stay Small?

There are several reasons why a cat may not grow to its full size. In fact, you may discover that your cat still looks like a kitten during its juvenile years, when it should experience a growth spurt. This may be caused by:


Certain cat breeds are naturally small. A person unfamiliar with breed-specific traits may think that their cat is undersized when in reality, it’s perfectly healthy and average. Small breeds include:

  • Munchkin
  • Singapura
  • Devon rex

Even full-grown cats can still look like kittens when they are one of these smaller breeds. Other types of cats are naturally slim, which can make them look underweight to the untrained eye. These include:

  • Siamese cats
  • Balinese
  • Oriental longhair

Aside from that, different cat breeds grow to their full size at different rates. Large cats, like Maine coons, can take anywhere between 4-5 years to reach their full size. Small and average cats, like domestic lines, generally take 1 year to grow fully.

The best way to judge if your cat is undersized or underweight is to compare it to the average weight and size of the breed. A body condition score chart is handy to confirm the state of your cat. Consult a vet if you are ever concerned about the results you find.

why is my cat so small and skinny?


Cats display sexual dimorphism, with female cats growing smaller than male cats. There can be quite a gap between cats of two different sexes, even if they are from the same litter.

Be aware that neutering cats before sexual maturity can cause them to remain smaller than cats neutered in adulthood. Without access to their sex hormones, their bodies are unable to fill out or bulk up.


Illness may cause felines to lose weight rapidly or slowly over time, depending on the condition. This can leave your cat appearing much smaller than even a few weeks ago.

In young cats, illness and parasites can make it appear like the kitten isn’t growing. What you are witnessing is the kitten’s growth being stunted and interrupted by the illness.

There are a number of illnesses known for causing stunted growth and weight loss in cats. A few of these include:

  • Diabetes
  • Tapeworms
  • Hyperthyroidism
  • Cancer
  • FIP (Feline Infection Peritonitis)

Other illnesses and diseases, like dwarfism and bone deformities, can also impact a cat’s growth. Any parasite that skims nutrients from its host will have a serious effect. For example, according to Veterinary Parasitology, stunted growth is a symptom of lungworm. This can often be your first warning sign, making it wise to consult a vet as soon as:

  • Your kitten stops growing for weeks at a time.
  • Your adult cat begins losing weight consistently, despite regular meals.


Malnourishment can be a side effect of an undiagnosed illness. However, it can also come from not getting enough nutrition due to;

  • A lack of food
  • An abundance of poor-quality food

A full-grown cat without adequate nutrition will lose weight and remain underweight until its diet is improved. A growing cat or kitten lacking in nutrition will experience stunted growth. Even if you fix the kitten’s diet, its growth may be forever impaired. The extent of this depends on the severity of the malnourishment.

Post-Birth Weight Loss

Female cats that have recently given birth will see rapid change in their overall weight. In particular, a mother cat will lose about 40% of her overall weight within a few days. That’s not the end of the story, however. Lactation is a taxing process and will cause further weight loss.

It is vital to provide pregnant and lactating mothers with plenty of high-quality food and multiple meals per day. There are special blends made specifically for these cats so that they can weather the change safely.

How To Make Your Cat Grow Big

We all want our cats to grow healthy and strong. You can take several steps to ensure that your cat is well-equipped to grow to its full size.

Proper Nutrition

Malnourishment during any point before maturity can lead to permanently stunted growth. Unfortunately, this is not reversible. Even with a vet’s intervention and a new diet, stunted growth cannot be cured, only prevented. The severity of the condition depends on:

  • How bad the malnourishment was
  • How long the malnourishment lasted

The most crucial way to ensure that your kitten grows to its proper size is to offer balanced meals on a steady basis. Kittens grow rapidly in their first 6 months, gaining roughly a pound per month. They need 2-3 high-quality meals per day. Leaving a dish of kitten kibble out for grazing is a smart way to avoid complications.

Adult cats may not be growing like kittens are, but they still need balanced diets. Ideally, this means 2 meals a day, or a grazing bowl and 1 meal a day. Cats that require a specific diet for weight gain will include:

  • Those with special dietary requirements
  • Those recovering from illness or injury

It is best to consult a vet for the ideal food plan. That’s especially true if you’ve just found your runaway cat and discovered it had lost a drastic amount of weight. According to the Journal of Veterinary Emergency and Critical Care, recovery is possible with proper care and supportive therapy.

full grown cat looks like kitten


Keeping up with worming medication is vital to ensuring your cat remains at a proper weight. Mild infestations won’t have a big impact on your cat’s health. Those infestations grow in size, however, and will strip your cat’s body and ingested food of its nutrients.

Aside from weight loss and stunted growth, parasites can eventually lead to death from organ complications and malnutrition. Stay up to date with anti-parasitics to avoid such dreadful outcomes.

Fair Share

Cats can be gluttons, and they can also be bullies. Multi-cat households will see a pecking order arise, especially around food time. This can result in one cat getting too little food while the other gets the lion’s share.

Consider feeding your cats in separate rooms. At the minimum, give them separate feeding dishes and place them at opposite ends of the room. Multiple grazing dishes can also be a way to avoid mealtimes being scarce. Any aggression at feeding time will mean that separate feeding rooms are the best option.

Anyone that has fostered stray kittens will recognize food-guarding behavior. Kittens will hiss and hunch over the food as they wolf it down. Sometimes, they will defend the food from others by smacking their paws at anything nearby and pushing it away.

Adult cats can do the same. Keep an eye out for this behavior and intervene to ensure everyone gets their share.

Full Grown Cat Still Looks Like Kitten

Cats that are malnourished or experiencing severe illness or parasitic infection can struggle to reach their full size. Young cats and kittens may even see their growth permanently stunted. Severely ill kittens may appear to not grow at all despite having a healthy appetite.

This could be an indication of parasites, diabetes, cancer, FIP, or hyperthyroidism. It is best to take your cat to the vet as soon as possible if you suspect it is unwell.

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Richard Parker

I'm Richard, the lead writer for Senior Cat Wellness. I'm experienced in all cat health-related matters, behavioral issues, grooming techniques, and general pet care. I'm a proud owner of 5 adult cats (all adopted strays), including a senior cat who is now 20.

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