Why is My Cat Losing Weight? Is it a Sign of any Disease?

Why is My Cat Losing Weight

If your cat is not on a weight loss diet yet, they are still losing weight; this means there’s an issue that needs to be diagnosed and treated as soon as possible. 

To find out if your cat is actually getting slimmer, monitoring its weight monthly and checking for any important changes is preferable. The normal body weight for an adult cat is between 3.5kg and 5 kg. Of course, the normal weight depends on many factors, such as age, gender, and breed.

If you are wondering why your cat is losing weight, it is better to get a proper diagnosis from your veterinarian. This article will inform you about the possible reasons for this weight change and how they can be fixed. 

Why is My Cat Losing Weight: 4 Reasons

A sudden weight loss in a cat is almost always linked to an issue. There are so many medical and behavioral reasons for your cat to lose weight. To find out why your cat is getting slimmer, you need to start by monitoring your cat’s appetite. 

Check whether your cat has a good appetite, or it’s trying to eat but is incapable, or it’s barely eating. You need to consider your cat’s age, especially if they are a senior cat. 

1. Your Cat Has a Good Appetite

Here’s why your cat eats well but still loses weight.

  • Poor-quality cat diets

What is a poor-quality diet? It is a diet that is neither well-balanced nor contains all the nutrients needed for your cat to maintain good health. Also, it can even be a diet that contains some toxic foods for cats. 

These diets can cause your cat to lose weight, affect its growth, and even cause health issues.

  • Maldigestion 

Your cat might be unable to digest its food due. This can be caused by the type of diet or decreased digestive enzymes due to a gastrointestinal disease or pancreatic insufficiency. 

  • Diabetes 

Weight loss is one of the important signs of diabetes in cats. Either it is diabetes type 1 or type 2. Why does diabetes cause weight loss? Because the cells in the body of a diabetic cat break down the fats in order to get their energy since they cannot absorb the glucose in the blood. Your cat might show increased thirst and urination as well.

  • Hyperthyroidism

If you ask why your cat is losing weight but eats a lot constantly, you might need to consider hyperthyroidism. Cats with hyperthyroidism are usually very skinny because they burn calories so fast due to their thyroid’s excessive production of the hormone thyroxine. These felines have an accelerated metabolic rate making them always hungry and always skinny.

  • Parasitism

Internal parasites are a very common reason for cat weight loss. Intestinal worms will lead to the malabsorption of nutrients. Some might say that the worms are eating the food in the cat’s intestines. Usually, parasites show symptoms other than weight loss, for example, diarrhea and vomiting. 

  • Lactation and pregnancy

Cats used for breeding are usually very underweight. They need to produce milk for their offspring, which demands a lot of energy and good nutrients. A mother cat’s appetite increases a lot while pregnant and breastfeeding. Unfortunately, unethical breeders do not always provide the mother with enough high-quality food, which leads to a lot of weight loss.

2. Your Cat is Unable to Eat

If your cat is in pain, it won’t be able to eat even if they are hungry and have a good appetite. Many reasons can make your furry friend unable to eat, including: 

  • Dental disease 

Your cat might have an oral disease causing them to stop eating and therefore lose weight. If you notice that your cat’s gums are inflamed, this means they have gingivitis that can be due to bad oral hygiene or a viral infection.

  • Oral tumor

Oral tumors cause a lot of pain for your cat making them unable to chew their food. This is usually more common in older cats.

  • Dental fracture

A loose tooth or a fractured tooth can make your cat uncomfortable and prevent them from enjoying its food. Dental fractures can be a consequence of feeding your cat chicken bones or your cat chewing on a foreign body, or even a bacteria and tartar build-up. 

  • Pharyngeal disease

Pharyngeal diseases can be feline calicivirus, herpesvirus, tonsillitis, or upper respiratory tract infection. These diseases cause a lot of pain in your cat’s mouth and alter the immune system. It is important to vaccinate your kitty and take oral health seriously in order to prevent these diseases. 

3. Your Cat Has a Bad Appetite

What causes cats to lose weight and stop eating?

  • Your cat doesn’t like the food

Cats are known to be very picky. It is advised to switch flavors and add some treats and new foods to your cat every once in a while, so they don’t get bored.

  • Viral infection 

Feline infectious peritonitis, feline immunodeficiency virus, and feline leukemia virus cause a very remarkable loss of appetite. These diseases can be very deadly and need urgent treatment.

  • Liver diseases and kidney diseases 

Liver diseases like hepatitis and hepatic lipidosis or kidney diseases have a common symptom: weight loss due to a bad appetite. 

  • Pancreatitis 

Other than the loss of appetite, cats with pancreatitis produce fewer enzymes that help digest and absorb nutrients leading to malnutrition.

  • Neoplasia

Cats with neoplasia lose weight and appetite because the cancerous cells demand more energy than the normal ones, and most of them take their energy and nutrients from the muscles. 

  • Stress

If your cat is going through a stressful event, for example, a new home or a new cat in the house, it can stop eating due to fear and stress. 

3. Your Senior Cat is Losing Weight

Senior cats usually have more diseases than adults or kittens. Most of these diseases cause weight loss. This is why performing regular blood tests for your senior friend is important.

  • IBD

IBD, also known as inflammatory bowel disease, is characterized by chronic inflammation in the gastrointestinal tract. This inflammation affects the absorption of nutrients and causes discomfort for your cat, making them feel sick and unable to eat.

  • Hyperthyroidism 

With age, cats are more susceptible to developing hyperthyroidism. It is less common to find a young cat with hyperthyroidism.

  • Renal disease

Cats with the renal disease lose a lot of protein in their urine, and they lose their appetite as well, leading to weight loss.

  • Dental disease

Dental diseases are very common in older cats. Some of them even lose most of their teeth. It is important to consider this and provide them with a kind of food they can easily digest. 

  • A decline in food digestibility

With age, both fats and proteins become less digested in older cats. There are not enough studies that can explain the reason why this happens. 

Treatment of Underweight Cats 

Your veterinarian will choose the best treatment for your cat depending on the reason behind the weight loss.

  • If your cat is losing weight due to malnutrition, your vet will prescribe good-quality cat food for weight gain.
  • If your cat is losing weight due to parasites, then treatment for worms is needed. 
  • If your cat is unable to eat due to oral disease or a tumor, then your veterinarian will perform the surgery needed to help your cat become more comfortable while eating.

In most cases, your cat will be prescribed the right diet for its condition and some vitamins that can help them gain weight.

How Can You Know That You Are Feeding Your Cat Right

The following list will help you identify if you are giving the right food to your cat.


Cats between 2 months old and 12 months old need kitten food that contains more calories and nutrients than the food made for adult cats that are 12 months plus. When the cat becomes almost 7 years old, you can start switching to senior cat food.


In order to make sure that the quality of food is good, you can simply head to your veterinarian’s clinic and ask for help. Please stay away from pet food sold in markets and get your cat what they deserve from your vet’s clinic.


It is important to know how much to feed your cat. Overfeeding or underfeeding can both cause health issues for your cat. You can find the quantity recommended for feeding your cat on every bag of food, depending on their age and weight.

woman feeding nuts to the cat
Image credit: Africa Studio, Shutterstock


If your cat has a chronic health issue, it will need medical food. Diabetic cats or cats with kidney, liver, or gastrointestinal diseases have specific diets to help them improve.


Some breeds require different kinds of food. For example, cats with long hair are more susceptible to hairballs. This is why they have a specific food that helps eliminate hairballs.

Finishing Line

There can be a lot of reasons why your cat is losing weight. You can start by ensuring you are giving your cat the right food and quantity. You can make sure to give more attention to your cat’s dental health. Suppose you already do that, but you still wonder why your cat is losing weight. In that case, it is preferable to contact your veterinarian to make a diagnosis and start the treatment as soon as possible. 


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