Countless health complaints can cause weight loss in cats. It’s a very vague symptom that can be just as related to the digestive system as it can be to the cardiovascular system, and just as benign as it can be an urgent emergency. It’s also tough to spot in some cats, particularly those with long or thick and fluffy fur.

Thankfully, the Emergency Fund vet is here to answer all your feline weight loss questions — and when you should worry about it.


  1. Causes of Weight Loss in Cats
  2. Older Cat Losing Weight but Still Eating
  3. Why is My Cat Losing Hair and Weight
  4. Cat Losing Weight and Vomiting
  5. Why Does Your Cat Drink a Lot of Water and Lose Weight
  6. FAQ
  7. Conclusion

Causes of Weight Loss in Cats

Weight loss in any animal often indicates a lack of food. Are you feeding your pet the right amount of food for their breed, age, size, and lifestyle? If you are, perhaps other pets in your household are eating it, or wildlife (such as rodents) are helping themselves to it.

A cat suddenly losing weight can also have medical roots. On its own, weight loss isn’t a symptom you can make a diagnosis with. In the same way as with humans, a wide and varied mix of medical conditions causes weight loss in cats, including:

Diagnostic testing, along with a list of other symptoms, will help you and your vet discover the underlying cause of your cat's weight loss.

Older Cat Losing Weight but Still Eating

Hyperthyroidism is a common cause of weight loss in older cats that are still eating and drinking as they usually would. According to PetMD study, cats over the age of eight are more at risk, but the average age of diagnosis is around 13 years.

If your senior cat is losing weight but still eating due to hyperthyroidism, you will notice other symptoms such as increased urination, increased appetite and thirst, more vocal noises at night, and sleeping less than usual.

Cats also have a higher chance of being diagnosed with cancer as they get older. Other symptoms, along with feline weight loss, depend on the location of the cancer. Bowel cancer, for example, usually comes with bloody stools. Lung cancer affects the respiratory system, so it comes with coughing, a rasping meow, a bloody mouth, and/or vomit.

Why is My Cat Losing Hair and Weight

Hair and weight loss together are associated with stress and anxiety, certain types of cancer, pregnancy or nursing, hyperthyroidism, gastrointestinal problems, and bacterial or fungal infections. Parasites and ringworms are also common culprits for the two symptoms combined.

Even with two symptoms, the causes are wide and varied, affecting widely different parts of the body. If you notice your pet losing weight, hair, or both, make an appointment with a vet. Blood tests, urine and stool tests, physical examinations, and other diagnostic testing will allow for the correct treatments or therapies.

Cat Losing Weight and Vomiting

Any cat condition that causes vomiting and/or an upset stomach can also cause weight loss. The longer the pet suffers from vomiting, the more weight it will lose.

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Irritable bowel disease, also known as IBD, is a medical condition that can cause cats to lose weight and hair. Other symptoms of IBD in cats include a decreased appetite, a grubby or scruffy look to the fur, and blood in your cat’s poop.

It’s common for cats to have allergies to foods such as dairy products, fish, chicken, beef, and more. This is especially the case if they are frequently exposed to the allergen. Gastrointestinal symptoms are less common than skin-related ones, such as excessive scratching, but they can still occur.

These include foul-smelling gas, loose and foul-smelling stools, and an itchy backside. You may notice your pet dragging their backsides across the floor in a bid to ease the itch.

Why Does Your Cat Drink a Lot of Water and Lose Weight

Kidney disease will see your cat drinking a lot of water and losing weight, along with other symptoms such as bad breath, vomiting, urinating more, lethargy, and disinterest in food.

Weight loss due to kidney disease, which is referred to as ‘chronic’ if symptoms persist for longer than three months, is slow and steady. It rarely causes fast weight loss.


What is healthy weight loss for cats?

It is not healthy for cats to lose more than one pound per month, but this does depend on start weight, goal weight, health conditions, and other factors.

What to feed an older cat that is losing weight?

A vet can advise on the right diet for an older cat that is losing weight, specifically for their medical needs. Senior cats have different dietary requirements than kittens, adolescents, and adult cats. Reduced movement means fewer necessary calories and older cats also need nutrients that target age-related feline problems. Senior cats require senior-specific complete cat food.

My cat smells bad and is losing weight – why?

The answer to this question comes down to which end of your cat smells best. Chronic kidney disease causes bad breath, also known as halitosis. IBD, on the other end, causes foul-smelling gas and poop.


Weight loss in cats is a cause for concern. You should tell a vet as soon as you notice it. Although it’s a symptom of something benign and easy to treat, it’s also a symptom of potentially deadly diseases that will kill if they aren’t diagnosed and correctly treated.

Why not have a chat with one of Petcube’s 24/7 qualified and licensed veterinarian if you’re worried about your cat’s weight or have other concerns?

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