Cat Losing Weight: Causes, When to Worry, and What to Do

Is your cat losing weight? If so, the cause depends on one question: Are they still eating?

A cat who’s ravenous but getting thinner likely has hyperthyroidism, which affects roughly 10% of cats older than 10 years. A cat who’s stopped eating could have kidney disease, cancer, or gastrointestinal issues.

If weight loss is sudden (more than 10% in a week) or your cat hasn’t eaten in 24 hours, call your vet immediately. If it’s gradual, start tracking appetite and symptoms to help your vet diagnose the problem.

Below, we explain the common causes of cats losing weight and how to manage each.

Why Is My Cat Losing Weight?

Unexplained weight loss in cats can have many causes, from changes in appetite to underlying health conditions. Your cat’s age, eating habits, how quickly they’re losing weight, and any other symptoms can all help narrow down what’s going on. Common causes of weight loss in cats include:

• Hyperthyroidism
• Chronic kidney disease
• Diabetes mellitus
• Gastrointestinal disease
• Cancer
• Dental disease
• Intestinal parasites
• Stress
• Chronic pain
• Infections
• Problems absorbing nutrients

The pattern of weight loss can also provide useful clues. A cat that is losing weight despite eating normally or even eating more may have a different underlying problem than a cat that has also losttheir appetite.

Pay attention to whether your cat is eating more or less than usual, drinking more water, vomiting, having diarrhea, or showing changes in their energy or behavior. These details can help your veterinarian determine what may be causing the weight loss.

Why Is My Older Cat Losing Weight?

If you’re wondering why your older cat is losing weight, you should know age alone isn’t the reason. Older cats are more likely to develop health conditions that can affect their appetite, digestion, metabolism, or ability to maintain muscle mass.

Common causes of weight loss in older cats include hyperthyroidism, chronic kidney disease, diabetes, gastrointestinal disease, cancer, dental disease, and chronic pain. Some conditions can cause weight loss even when a cat continues to eat normally or has an increased appetite.

Older cats can also naturally lose some muscle as they age, a process known as sarcopenia.

However, significant or ongoing 

weight loss shouldn't be attributed solely to aging. Losing muscle and body fat can also be a sign of an underlying issue, like cachexia.

If your senior cat is losing weight without an intentional change to their diet, schedule a checkup with your vet.

Pay particular attention if your older cat is losing weight but still eating normally or eating more than usual. Hyperthyroidism and diabetes can both cause weight loss despite a normal or increased appetite, so mention these changes to your veterinarian.

How to Tell If My Cat Is Losing Weight

Cats can lose weight slowly, so it’s often hard to notice right away. This is even more true for long-haired cats, since their fur can hide changes in their body shape.

By the time you see obvious changes, your cat may have already lost a lot of fat or muscle. Check your cat’s body regularly for these signs:

• When you gently run your hands over your cat’s body, you should be able to feel their ribs with light pressure, but they shouldn’t be sharply visible or sticking out.
• You may also notice their spine and hips becoming more prominent. These areas should have a thin layer of fat covering them, so if you can suddenly feel the bones more clearly, your cat may be losing too much weight.
• Take a look at your cat from above, too. They should have a slight inward curve behind their ribs, but a very pronounced or concave waist can be a sign that they’ve lost a significant amount of weight.
• Pay attention to their hind legs and haunches as well. If they start looking noticeably thinner, your cat may be losing muscle along with body fat.
• Finally, check their coat for any changes. Weight loss or illness can leave your cat’s coat looking dull, greasy, matted, or less well-groomed than usual.

How to Track My Cat’s Weight at Home

Weighing your cat regularly can help you spot weight loss before it’s easy to see.

If your cat is small, you can use a baby scale or a pet scale. If you don’t have one, try this method:

1. Weigh yourself and record the number.
2. Pick up your cat and weigh yourself again.
3. Subtract your weight from the combined weight.
4. Record your cat’s weight.
5. If your cat is losing weight, weigh them once a week.

If your cat loses more than 5% of their body weight in a month, talk to your vet. For a 10-pound cat, that’s just half a pound.

If your cat is losing weight and you don’t know why, don’t wait until they look skinny to find out what’s wrong.

Why Is My Cat Eating But Still Losing Weight?

If your cat is eating as usual or even more than normal but still losing weight, hyperthyroidism or diabetes could be the reason.

1. Hyperthyroidism

Hyperthyroidism is a common hormone problem in older cats, usually those over 8 to 10 years old. It often causes noticeable weight loss even though your cat may be eating more.

The thyroid gland makes hormones that control how fast the body uses energy. In hyperthyroidism, too much thyroid hormone speeds up metabolism, so the body burns calories and muscle faster than normal.

Signs of hyperthyroidism can include:

• Increased appetite
• Weight loss
• Restlessness or hyperactivity
• Increased thirst and urination
• Vomiting or diarrhea
• Increased vocalization
• A fast heart rate
• Poor or unkempt coat

Research shows that muscle loss occurs in over 75% of hyperthyroid cats, even before fat loss becomes obvious. This is why a hyperthyroid cat can look relatively normal but is actually losing deep muscle tissue. Even after treatment, about 45% of cats don’t fully regain normal muscle mass.

⚠️ What You Might Miss: Many owners describe their hyperthyroid cats as acting “younger” or “more energetic” in early stages. Although these seem like positive signs, the cat’s metabolism is actually in overdrive.

If your senior cat suddenly becomes more active and hungrier but is losing weight, that’s a red flag.

2. Diabetes Mellitus

Diabetes is another reason a cat might lose weight even if they’re still eating.

If insulin isn’t working right, your cat’s body can’t use sugar for energy. Instead, it starts to break down fat and muscle.

Other signs include:

• Increased thirst
• Increased urination
• Increased appetite
• Lethargy
• Weakness
• A plantigrade or “walking on the hocks” stance in advanced cases

Your veterinarian can check blood glucose levels and urine for glucose to investigate diabetes.

3. Intestinal Parasites

Intestinal parasites can interfere with your cat’s digestion and nutrient absorption, making it harder for them to maintain a healthy weight. Depending on the type and severity of the infection, parasites may also cause diarrhea, vomiting, poor appetite, anemia, or a dull coat. Some infected cats show few or no obvious symptoms.

Cats that go outdoors, hunt, eat prey, or come into contact with contaminated feces or soil may have a higher risk of exposure.

Kittens are also particularly susceptible to some intestinal parasites Kittens are especially susceptible to intestinal parasites like roundworms, hookworms, and protozoa such as Toxoplasma gondii.

If your cat is losing weight without an obvious explanation, your veterinarian may recommend a fecal examination to look for evidence of parasites. Because some parasites are shed intermittently, a single negative test does not always rule out an infection.

Why Is My Cat Not Eating And Losing Weight?

If your cat is losing weight and has stopped eating, it’s more serious and needs attention.

Possible causes include chronic kidney disease, gastrointestinal disease, dental pain, pancreatitis, cancer, and other illnesses.

1. Chronic kidney disease

CKD is one of the most common conditions in older cats. 42% to 82% of cats with CKD suffer from weight loss, often losing a median of 8.9% of body weight in the year before diagnosis.

When the kidneys don’t work well, waste builds up in the blood. This can make your cat feel sick and not want to eat. Over time, they may also lose muscle.

Signs of CKD can include:

• Increased thirst
• Increased urination
• Decreased appetite
• Weight loss
• Vomiting
• Lethargy
• Weakness
• Poor coat quality
• Bad breath

Your veterinarian may use bloodwork, urinalysis, and SDMA testing to evaluate kidney function.

2. Gastrointestinal disease (IBD, Lymphoma, Pancreatitis)

Problems like inflammatory bowel disease, digestive cancers, or pancreatitis can make your cat lose weight by lowering their appetite, making them feel sick, or stopping them from absorbing food properly.

Watch for:

• Decreased appetite
• Vomiting
• Diarrhea
• Lethargy
• Abdominal discomfort
• Progressive weight loss

Your veterinarian may recommend bloodwork, X-rays, ultrasound, or a biopsy depending on your cat’s symptoms.

3. Dental disease

Dental disease can make eating painful, causing your cat to eat less and gradually lose weight. Cats are particularly good at hiding mouth pain, so changes in eating habits may be one of the first signs that something is wrong.

You may notice your cat dropping food while eating, chewing on one side of their mouth, pawing at their face or mouth, drooling, having bad breath, or avoiding dry food. Some cats may also lose interest in food altogether when their mouth becomes too painful.

Common dental problems in cats include periodontal disease, gingivitis, and tooth resorption. If your cat is losing weight and showing signs of mouth discomfort, your veterinarian can examine their teeth and gums and recommend appropriate treatment.

4. Cancer

Cancer can cause gradual, unexplained weight loss in cats by affecting appetite, digestion, nutrient absorption, and the way the body uses energy. Some cats with cancer also develop a condition called cancer cachexia, where metabolic changes lead to the breakdown of fat and muscle even when the cat is still getting enough nutrients.

Weight loss may occur alongside other symptoms, such as reduced appetite, vomiting, diarrhea, lethargy, or behavioral changes. The signs can vary depending on the type of cancer and which part of the body is affected.

Not all cancers cause a visible lump, so don't wait for a noticeable mass before having unexplained weight loss checked. If your cat is steadily losing weight without an obvious reason, your veterinarian can perform a physical examination and recommend further testing if needed.

When Should I Call the Vet Immediately?

Some reasons for weight loss need quick attention from a vet.

Call your vet right away if your cat:

• Hasn’t eaten for 24 hours
• Is losing weight rapidly
• Is repeatedly vomiting or has severe diarrhea
• Has difficulty breathing or is open-mouth breathing
• Collapses or cannot stand normally
• Is severely lethargic or unresponsive
• Has yellow gums, eyes, or skin
• Shows obvious signs of pain
• Has stopped eating and is becoming increasingly weak

Cats that go without food for too long can get fatty liver disease, which can be very serious or even life-threatening.

What Tests Will My Vet Run If My Cat Is Losing Weight?

If your cat is losing weight and you don’t know why, your vet will usually start by checking them over and asking about their health history.

Depending on your cat’s age and symptoms, testing may include:

Procedure	What It Can Check
Physical examination	Body condition, thyroid gland, teeth, heart, abdomen, hydration
CBC and chemistry panel	Kidney and liver function, glucose, electrolytes, blood cells
T4 thyroid test	Hyperthyroidism
Urinalysis	Urine concentration, glucose, protein, infection
Blood pressure	Hypertension associated with kidney disease or hyperthyroidism
Fecal examination	Intestinal parasites
X-rays	Tumors, organ changes, obstruction, and other abnormalities
Ultrasound	Abdominal organs, masses, and gastrointestinal disease
FeLV/FIV testing	Certain viral infections
Endoscopy	Gastrointestinal disease
Biopsy	IBD, lymphoma, and other tissue abnormalities

Your vet will decide which tests your cat needs based on their age, health history, exam, and symptoms.

How to Support My Cat’s Appetite and Weight at Home

While your vet looks for the cause of your cat’s weight loss, you can try to make eating more appealing for your cat.

Try warming your cat’s wet food slightly to make it more aromatic and appealing, but always check the temperature before serving it.

If your cat is being picky, offer different textures to see what they prefer. Some cats enjoy smooth pâté, while others prefer chunks or shredded food.

You can also try offering smaller meals throughout the day instead of one or two larger portions, especially if your cat has a reduced appetite.

Make mealtimes as calm and comfortable as possible by placing their food in a quiet spot away from other pets, loud noises, and other distractions.

If your cat still isn’t eating, talk to your vet about ways to support their appetite. They may recommend medication such as mirtazapine to encourage eating or an anti-nausea medication if nausea is making it difficult for your cat to eat.

What to Feed A Cat That Is Losing Weight

If you’re not sure what to feed an older cat that’s losing weight, don’t just pick the food with the most calories.

The best diet for your cat depends on the reason for their weight loss. For example:

• A cat with hyperthyroidism may need a specific treatment diet if your veterinarian recommends one.
• A cat with kidney disease may benefit from a veterinary renal diet.
• A cat with gastrointestinal disease may need a highly digestible, novel-protein, or other therapeutic diet.
• A cat with dental pain may prefer soft food that is easier to eat.

If your older cat just isn’t eating enough, try making their food more tempting. Warm up wet food a little, offer different textures, and give smaller meals more often.

Consider nutritional supplements

If your cat isn’t eating enough, nutritional supplements can sometimes help provide extra calories and nutrients while you work with your vet to address the underlying cause of their poor appetite.

High-calorie nutritional gels, pastes, and other supplements are designed to pack more energy into a small amount of food. This can be useful when your cat is eating only small portions and needs additional calories to help maintain their weight.

However, these products should support your cat’s regular diet rather than replace a complete, balanced food. Your vet can help you choose a supplement based on your cat’s weight, nutritional needs, and the reason they aren’t eating.

Omega-3 fatty acids

Omega-3 fatty acids, particularly EPA and DHA, can support your cat’s overall health and help regulate inflammatory processes in the body. They are commonly used as part of nutritional support for cats with conditions that may involve inflammation, such as joint or skin problems.

Fish oils are a common source of EPA and DHA. Our Salmon Oil for Cats provides omega-3 fatty acids and can be added to your cat’s food.

Omega-3 supplements won’t directly treat the cause of a poor appetite, so they’re generally better viewed as supportive nutrition rather than an appetite stimulant.

Ask your vet whether an omega-3 supplement is appropriate for your cat, especially if they have an underlying health condition or take medication.

CBD oil for cats

Some pet owners use CBD oil as part of their cat’s wellness routine, particularly when they’re looking to support comfort or relaxation. CBD interacts with the body’s endocannabinoid system, which plays a role in processes such as stress, pain perception, and inflammation.

However, research on CBD in cats is still limited, and there isn’t enough evidence to recommend it as a treatment for appetite loss itself. If your cat has suddenly stopped eating, it’s more important to find and treat the underlying cause than to rely on CBD to encourage them to eat.

Our CBD Oil for Cats does not contain essential oils or ingredients known to be harmful to cats. Talk to your vet before giving your cat CBD, particularly if they have a medical condition or take other medications, as CBD may interact with certain drugs.

Warning: Never try to force-feed a cat that is vomiting or may have a blockage in their stomach or intestines. If your cat hasn’t eaten for a full day, contact your vet rather than relying on supplements or home remedies.

How to Prevent Weight Loss in My Cat

You can’t always prevent weight loss, but keeping an eye on your cat’s health can help you spot problems sooner. For cats that are over 7 years old:

To prevent unhealthy weight loss in cats, focus on regular feeding, monitoring, and catching health problems early.

• Feed a complete, balanced diet

Choose a nutritionally complete cat food that meets your cat’s life-stage needs. Cats have different calorie and nutrient requirements depending on their age, size, activity level, and health.

• Keep track of how much your cat eats

Pay attention to changes in your cat’s appetite rather than assuming they are simply being picky. If they consistently eat less than usual, measure their portions and keep track of how much they actually finish.

• Monitor your cat’s weight

Weighing your cat regularly can help you notice gradual weight loss before it becomes obvious. This is especially important for older cats or cats with ongoing health problems.

• Make mealtimes comfortable

Feed your cat in a quiet area where they can eat without being disturbed by other pets, loud noises, or household activity. Some cats may also eat better when their food and water are kept away from their litter box.

• Keep an eye on dental health

Dental pain can make eating uncomfortable and may cause your cat to eat less over time. Regular veterinary dental checks can help identify problems such as periodontal disease, painful teeth, or inflammation.

• Schedule regular veterinary checkups

Routine checkups can help detect conditions that may cause gradual weight loss, including dental disease, digestive problems, kidney disease, diabetes, and hyperthyroidism. Early treatment can help prevent these conditions from affecting your cat’s weight further.

• Act quickly if you notice changes

Unexplained weight loss isn’t something to manage with extra food or supplements alone. If your cat is losing weight, eating less, vomiting, having diarrhea, drinking more than usual, or behaving differently, contact your vet to find out what’s causing it.

What Does Your Cat’s Appetite Tell You?

When your cat is losing weight, the first question to answer is: Are they still eating?

A cat who’s ravenous but shrinking likely has hyperthyroidism. A cat who’s stopped eating and is wasting away needs a workup for kidney disease, GI issues, or cancer. But remember: 15% to 20% of hyperthyroid cats also have masked CKD that won’t show up until the thyroid is treated.

Don’t wait for your cat to become skeletal before seeking help. A 10% weight loss in a cat is significant and warrants immediate veterinary evaluation.

Early diagnosis of hyperthyroidism, CKD, or other conditions gives you the best chance of managing the disease and maintaining your cat’s quality of life.

Frequently Asked Questions

Why is my cat losing weight?

A cat may lose weight because of hyperthyroidism, diabetes, kidney disease, gastrointestinal disease, cancer, dental disease, parasites, stress, or other health problems. The cause is more likely to be medical if the weight loss is progressive or occurs without a change in diet or activity.

Why is my cat losing weight but still eating?

If your cat is losing weight but still eating, hyperthyroidism and diabetes are important possibilities. Hyperthyroidism can dramatically increase metabolism, while diabetes prevents the body from using glucose normally. Your veterinarian can use bloodwork and other tests to determine the cause.

What should I feed an older cat that is losing weight?

The best food depends on the reason your cat is losing weight. A cat with kidney disease may need a renal diet, while a cat with gastrointestinal disease may need a different therapeutic diet. If your older cat is losing weight, consult your veterinarian before making a major dietary change.

Why is my elderly cat losing weight but still eating?

An elderly cat losing weight despite eating should be examined by a veterinarian. Hyperthyroidism and diabetes can cause weight loss even when appetite remains normal or increases. Other possibilities include gastrointestinal disease and parasites.

How much weight loss is concerning in cats?

Losing more than 5% of body weight in a month is significant enough to discuss with your veterinarian. More rapid or substantial weight loss is particularly concerning, especially when accompanied by appetite changes, vomiting, diarrhea, lethargy, or other symptoms.

Can kidney disease cause weight loss even with normal bloodwork?

Early kidney disease can sometimes be difficult to detect using traditional markers alone. Your veterinarian may recommend additional testing, including SDMA and urinalysis, when kidney disease is suspected.

How long can a cat go without eating?

A cat that hasn’t eaten for 24 hours should be taken seriously. Prolonged food refusal can lead to hepatic lipidosis, or fatty liver disease, particularly in overweight cats. Contact your veterinarian if your cat stops eating rather than waiting several days to see whether their appetite returns.

Should I change my cat’s food if they’re losing weight?

Not necessarily. The appropriate diet depends on the underlying cause. Changing food without identifying the problem can sometimes make things worse, particularly if your cat has kidney disease or another condition requiring a specific therapeutic diet.