Get

In Your Inbox

Catster is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

Why Is My Cat Always Hungry But Still Skinny? Vet Explained Causes & Care Guide

Skinny cat

You know that something strange is going on with your cat if they are always hungry but keep getting skinny. So what could be causing this? This article explores some of the common reasons this could be occurring, and what you should do. One thing is for sure though, weight loss can be a sign of a health issue and should be taken seriously.

divider 1 paws

The 6 Causes of Weight Loss Despite a Good Appetite

Here are some of the more common causes of weight loss in cats that are still eating a lot. If your cat is constantly pestering for food but appears to be underweight, these are some of the reasons why:

1. Cat Hyperthyroidism

This condition is commonly seen in older cats, and perhaps gives us the most obvious example of a skinny, hungry cat. These cats can often have quite dramatic weight loss, yet have excessively keen appetites. Sometimes other symptoms are seen too, such as tummy upsets, changes in temperament/activity, increased thirst, and an increased heart rate.

Hyperthyroidism is caused by the increased production of thyroxine, a hormone that controls metabolism. This occurs because the thyroid gland gets a growth—it’s usually benign, but in very rare cases a cancerous tumor can be the cause of these symptoms too (thyroid adenocarcinoma).

Diagnosis is usually made from a physical examination and blood samples. Your veterinarian may be suspicious of the condition after examining your cat. They can sometimes feel the enlarged gland in the throat, and hear abnormalities in the heart such as an elevated rate and change in rhythm. A blood test is advised to screen for other conditions and to measure your cat’s thyroxine levels (called T4).

If your cat is found to have hyperthyroidism there are a few different treatment options.
  • Medication – daily medication of tablets or liquids can help suppress your cat’s thyroid hormone production and bring symptoms under control. He will need regular monitoring through checkups and blood tests.
  • Surgery – removal of the thyroid gland can be curative, meaning no ongoing treatment. However, there are some risks associated with this.
  • Diet – a prescription diet that has restricted iodine levels can stop your cat from producing the thyroid hormone. This does mean no treats or other food is allowed, as the diet won’t work. It’s also not very tasty, and some cats will not eat it.
  • Radioiodine therapy – considered the “gold standard” and curative in most cases. Radioiodine therapy for cats involves a stay at a referral hospital for several days. No ongoing monitoring will be needed afterward, but it can be expensive, and may not be suitable for some cats.

Hyperthyroidism can be managed with many cats leading to a good quality of life after diagnosis. Left untreated your cat could suffer from high blood pressure (leading to eye problems), digestive issues, and heart abnormalities. Untreated hyperthyroidism can eventually become fatal over several months.


2. Cat Diabetes

Diabetes mellitus (sugar diabetes) can cause cats to lose weight. They will also commonly have increased thirst and urinate more frequently, and some of these cats will have an increased appetite (called ‘polyphagia’).

Diabetes is caused by a reduced ability to produce insulin, the hormone that controls blood sugar levels. This can be type I, an autoimmune condition (common in humans but rare in cats), or type II, caused by abnormalities in the pancreas and also insulin resistance in the tissues in the body. It is much more common in overweight cats that aren’t very active.

Diagnosis is usually made after a physical examination and blood tests, which show high levels of glucose (sugar). Urine samples can also be useful as high levels of glucose can often be found here too.

Treatment often involves supplementing the cat with insulin, which is done through regular daily injections. Dietary management can be very useful in some cases too. Not treating diabetes properly can lead to complications such as problems with your cat’s nervous system, eyesight issues, and a serious condition called ketoacidosis which can be fatal.


3. Inappropriate Cat Diet

The cause of your cat’s weight loss could be an inappropriate diet such as an energy-activity mismatch. This might happen if a very energetic cat isn’t receiving enough food. Make sure you double-check the packet guidelines and are feeding for your cat’s ideal body weight. Also bear in mind that some cats will need a bit more than the guidelines (if they are very active), and equally some will need a bit less.

Making sure that your cat is on a good quality complete diet that is appropriate for their life stage (kitten, adult, senior) will help. Home-cooked diets can be very hard to get right and need advice from a board-certified veterinary nutritionist.

If you need to speak with a vet but can't get to one, head over to PangoVet. It's an online service where you can talk to a vet online and get the advice you need for your pet — all at an affordable price!

PangoVet_Mention-in-Content for PangoVet2 save money


4. Cat Parasites

Large numbers of parasites could cause weight loss. Worms such as roundworms and tapeworms living in your cat’s digestive tract can absorb some of the nutrients your cat is eating, causing them to lose weight.

Cats with parasites may also show other symptoms such as diarrhea or vomiting. To prevent this from happening you should ensure your cat has routine worming treatments, particularly if they are hunters or go outside a lot.

Cat wearing collar scratching and itching
Image Credit by: AlexanderDubrovsk, Shutterstock

5. Cat Stress

Some cats can eat more due to stress, but they may also be burning that off through nervous energy. Stress-induced vomiting may mean that they aren’t keeping down the food they are eating too.

Other signs of stress in cats include hiding away more than normal, having accidents in the house (urine and feces), and changes in temperament. Cats can become stressed by things such as moving house, a new baby in the home, new pets moving into the house, and new cats in the neighborhood outside. It is important to rule out other health conditions before attributing your cat’s lean weight to stress.


6. Cat Gastrointestinal Disease

There are a variety of digestive disorders which could mean your cat may still have a keen appetite but may not be processing their food properly. Conditions such as inflammatory bowel disease and some cancers may cause vomiting or diarrhea. This can cause weight loss as your cat cannot effectively digest their food. If your cat is showing signs of poor digestion, then you should contact your veterinarian for advice.

divider 3 paws

What Will My Veterinarian Do?

If you are concerned about your cat’s weight and appetite, you should take your pet to your veterinarian for a check-up. If your cat goes outside a lot, you may not be seeing any vomiting or diarrhea that might be occurring, so do not assume it is not happening. Weight loss may be the only sign you notice.

Your veterinarian will give your pet a check-over initially but may also advise further tests. Blood samples can screen your cat’s general health by looking at the liver, kidneys, blood sugar, and thyroid hormones. Urine samples can screen for infections and elevated sugar levels, and fecal samples will identify any parasites or bacterial infections. Sometimes x-rays or ultrasound imaging may be required to reach a diagnosis.

Your veterinarian will talk you through the process step by step, and tailor any recommended diagnostics or treatment to your cat.

divider 1 paws

Conclusion

Weight loss can mean there is an underlying health condition occurring, so you should take any changes in your cat’s appetite and body condition seriously. Being underweight can also leave your cat weakened and less likely to be able to withstand infections and stresses. The sooner you take your pet to the veterinarian, the sooner a problem can be identified and dealt with—so don’t delay!

See also:


Featured Image Credit: Poto69, Shutterstock

Want content like this delivered to you?

Sign Up For Our Newsletter

News, insights, expert advice, and everything cat

* By submitting, you agree to our Terms & Conditions and Privacy & Cookies Policy.

How useful was this post?

Click on a star to rate (you can leave written feedback after clicking submit)

Help us improve Catster for pet parents!

Your feedback really matters.

What did you like about this post? Also how can we improve it?

Join the conversation

2 Responses

  1. Hi Dr. MacMillian,

    Thank you so much for this thorough description of what might be happening to my cat. One problem I have is that my cat doesn't let us pick her up. She is a rescue cat and experienced trauma before we got her.

    Even after 10 years Stevie gets triggered when we try to pick her up. She'll run off and hide lickety-split. Stevie does jump up on our laps if it is her decision to get some petting. The only time we have been able to contain her in a travel bag is if we give her some Benadryl to make her sleepy. What would you suggest in this situation? Is it cruel to do nothing.

    Stevie is 12 years old and has had a good life since we adopted her.

    Thank you for you advise.

    1. Hi Monica George-Halling. Catster’s customer service staff here. You may find these posts useful: https://www.catster.com/cat-behavior/why-cat-doesnt-want-to-be-held/. For transportation like vet visits, you could try training your cat: https://www.catster.com/lifestyle/how-to-crate-train-my-cat/. We hope this helps. Also, if you would prefer to speak directly with one of our vets, you can reach them at www.pangovet.com

Leave a Reply

You’re very welcome to leave a comment or question. Please know that all comments must meet our community guidelines, and your email address will NOT be published. Let’s have a positive and constructive conversation.

Talk With A Vet Online

Peace of mind,
anywhere, anytime

Affordable vet advice

TNR, Compassion, & Cats – TrapKing Humane Cat Solutions’ Story

You may recognize Sterling ‘TrapKing” Davis from The Drew Barrymore Show, the Disney+ documentary Pets directed by Bryce Dallas Howard, or Netflix’s Cat...

My Cat Ate a Poinsettia Leaf, Here’s What to Do (Vet Answer)

On almost every list of toxic plants for cats, especially holiday lists, you’ll see poinsettias listed. The good news is that poinsettias are...

Part-Time Apex Predator: Cyril’s Remarkable, But Selective, Hearing

Hi, I’m Dr. Karyn! Read my introduction to learn more about me and meet my five hilarious cats: Clutch, Cyril, Alex, Zelda, and...

5 Best Corner Cat Scratchers in 2025 – Reviews & Top Picks

For our cats, scratching is an instinctive behavior. While it might be irritating to notice a few claw marks on the side of...

More related

How Big Does an Abyssinian Get? Average Weight & Growth Chart

With a lean, elegant look, the Abyssinian cat strongly resembles the cat statues of Ancient Egypt. They’re a striking breed with exotic gold...

Ragdoll Cat Health Problems: 20 Vet-Reviewed Issues

As one of the most popular cat breeds, Ragdolls are known for their docile and placid temperament. Their trademark move is to go...

How Do Cats Walk? Our Vet Explains

Any cat owner whose ankles have fallen victim to a sneak attack from a playful kitty knows that sometimes you can’t hear them...

Can You Get Pink Eye From a Cat? Vet Approved Facts & Advice

If you’ve ever contracted pink eye, you know it’s an uncomfortable and contagious condition. What you might not know is that cats can...

Keep reading

Is Nephthytis (Arrowhead Plant) Poisonous to Cats? Vet-Reviewed Houseplants Examined

Nephthytis (arrowhead plant) is a common and popular houseplant due to its air-purifying properties. If you’re a plant and a cat lover, you may be wondering if nephthytis is poisonous to cats. The short answer is yes, nephthytis can be...

Catster_Is Nephthytis Poisonous to Cats

Can Cats Eat Plums? Vet-Reviewed Facts & FAQ

Cats are curious creatures that often conduct investigations with their mouths. While cats generally won’t eat foods that aren’t good for them, curiosity may get the better of them from time to time. You should do your best to keep...

Can Cats Eat Plums

What to Feed a Diabetic Cat to Gain Weight: Vet-Reviewed Health Tips

Diabetes has become an epidemic, not just in people but also in pets. Feline diabetes is most similar to type 2 diabetes in humans, meaning that weight management and diet are critical factors in controlling the condition. Cats with diabetes...

cat thin

Is Food Coloring Safe for Cats? Vet Approved Facts & FAQ

In addition to taste and smell, the color of food plays a large role in making our food look tasty or a drink look refreshing. Certain colors can stimulate the appetite or turn it off, and the culinary arts consider...

Catster_Is Food Coloring Safe for Cats

My Cat Stopped Grooming: Vet-Reviewed Reasons & Advice

As cat owners, we want to ensure that our pets are happy and healthy. Grooming is a common behavior for cats, and they can spend a significant part of the day grooming themselves, so when they suddenly stop, it can...

bengal cat grooming itself

My Cat Swallowed a Foreign Object: When to See a Vet

Cats love to play with anything that they can get their paws on, such as buttons, balls of paper, bits of string, threads, shoelaces, ribbons, cords, and yarn. Unfortunately, while playing with these seemingly harmless objects, our feline companions can...

a siamese cat getting examined by a vet at the clinic

When to Switch From Kitten Food to Cat Food? Vet-Reviewed Facts & FAQ

Cats, like people, have different nutritional and dietary requirements at different stages of life. Kittens have seemingly boundless energy, and they need to consume the nutrients to match this. When they cross into adulthood, they will be burning off a...

little kitten sitting by a bowl of milk

6 Best Clippers for Persian Cats in 2025 – Reviews & Top Picks

Cat clippers are great for quick touch-ups between trips to the groomer or to avoid the groomer altogether, but many owners run into issues with clipping the fur of certain breeds. Persians, for example, have long, fine fur that can...

White Persian cat staring