Lake Zurich Cat Owners: Is Your Cat Losing Weight but Still Eating?

Cats tend to lose weight when they are not eating enough. However, they can also lose weight even though they are still eating. This weight loss could be a sign of an underlying medical condition. Have your vet examine your cat to see what is going on.

The two most common reasons a cat could be losing weight but is still eating include hyperthyroidism and diabetes. These conditions are serious and require immediate care and attention.

cat losing weight but still eating

There are a plethora of health conditions in which your cat can lose weight. If your cat has an illness, you want to know early on to prevent further complications. Read on to find out what to do if your cat is losing weight but is still eating.

My Cat Losing Weight but Eating All the Time, Why?


Hyperthyroidism is an illness commonly seen in older cats. If your cat has been eating a lot but still losing weight, hyperthyroidism could be the culprit. This illness occurs when the thyroid gland becomes enlarged. This enlargement is typically due to a benign tumor that grows on the thyroid.

It is the thyroid gland’s responsibility to regulate the body’s metabolism. It also controls the heart, brain, muscle, and digestive functions. Hyperthyroidism occurs when the cat cannot eat enough food to keep up with their metabolism.

Some of the symptoms of hyperthyroidism involve weight loss, increased appetite, increased thirst, and urinating more than usual. Your cat may also have diarrhea, or they may frequently be vomiting. Some cats who have hyperthyroidism also experience bouts of hyperactivity and muscle wasting.

Increasing your cat’s food intake will not cure them of hyperthyroidism. Hyperthyroid cats can eat as often as they want and still not gain any weight. Eventually, hyperthyroidism can lead to serious health problems such as heart issues and hypertension.

These conditions require medical treatment to diminish the chance of becoming blind, having heart failure, stroke, or death. If you think your cat might be hyperthyroid, get to the vet as soon as possible.

The treatment your cat receives for their hyperthyroidism depends upon the individual circumstances of the cat’s condition. Radioactive iodine therapy  (see video) is the favored treatment for cats with hyperthyroidism.

The emitted radiation destroys abnormal thyroid tissue without harming the surrounding tissue or other glands. There is about a 95 percent success rate of curing hyperthyroidism this way.

It is rare for a cat to become hypothyroid after treatment, but your vet can prescribe thyroid medication to manage the condition if this occurs.


Diabetes mellitus may also be a reason for your cat losing weight. This disease is an endocrine disorder that impairs the way the pancreas creates insulin. This hormone is significant and is essential for regulating blood glucose.

Some of the symptoms of diabetes include weight loss, increased appetite, drinking more than usual, and urinating more than usual. Diabetes causes the starved cells to break down fats and proteins available in the body to utilize energy.

Cats with diabetes are often treated with injectable insulin. Diet changes are also necessary. You should feed your diabetic cat a higher protein diet, as diabetes can cause cats to lose muscle mass. Your veterinarian will help determine the correct amount of protein for your cat.

While it is true that diabetic cats need to watch their carbohydrate intake, it is essential to give a decent balance of protein and carbohydrates, so your cat does not lose more weight. Fiber can help in controlling blood sugar. Nutrition plays a key role in preserving a diabetic cat’s health.

What Are Some Other Causes of Weight Loss in Cats?

 Gastrointestinal Problems

Gastrointestinal issues can lead to weight loss in cats. If your cat has these issues, they will likely have diarrhea or be vomiting all the time. Inflammatory bowel disease, for example, can trigger weight loss even if your cat is still eating.

Some of the symptoms of inflammatory bowel disease in your cat include weight loss, bloody stool, chronic diarrhea, and lethargy. The indicators depend on which parts of the gastrointestinal tract are affected. An inflamed gut prevents the normal digestion of food, and nutrients are lost.

Some other causes may include food allergies or certain gastrointestinal infections. Because GI issues are tricky, they can trigger a lot of stomach discomfort in the cat. Your veterinarian may order a special diet for them to assist with nutrient absorption and decrease inflammation and irritation.

Intestinal Parasites

Intestinal parasites can prompt weight loss for your feline, even if they are still eating. If you own a cat who likes to prey on small rodents and rabbits, they may be exposed to gastrointestinal parasites such as roundworms and tapeworms.

Intestinal parasites and worms can prevent the absorption of nutrients, which can trigger weight loss. This intruder can cause vomiting, diarrhea, and bloating. Sometimes cats who are suffering from intestinal parasites do not display symptoms.

If your cat has intestinal parasites, your vet can give them the appropriate medication to rectify the situation, such as a dewormer treatment. Many dewormers come in liquid form, and it should not require much effort to administer them to your cat.

Regular wellness exams are recommended for your cat so that any problems like this can be quickly diagnosed and treated.

Kidney Disease

Kidney disease or renal insufficiency can develop as cats get older. The symptoms include weight loss and drinking more, and urinating more often than usual.

Your cat’s kidneys are vital for normal bodily functions, such as eliminating toxic metabolic waste products from the blood and regulating bodily fluids and hormones.

Some of the symptoms of chronic kidney disease in cats include weight loss, vomiting, bad breath, lethargy, increased thirst, and uncontrollable urination.

Certain factors such as kidney stones, frequent urinary tract infections, or hereditary disorders can make it more likely for a cat to develop kidney disease. As cats get older, the likelihood of them developing kidney disease increases.

Treatment for kidney disease in cats may include:

  • Fluid therapy for rehydration and balance of electrolytes
  • A high-quality restricted diet
  • Drug therapy for the possible underlying cause of kidney disease, such as anemia (if necessary)
  • Medications to lower blood phosphorus (if necessary)

If you think your feline might have kidney disease, take them to see your veterinarian as soon as possible.

When Should I Worry About My Cat Losing Weight?

If your cat is losing weight and you do not have them on a diet, this is cause for concern. Weight loss in cats is not always profound, but you should contact your vet if you notice them losing too much weight or losing weight too quickly. Some tips to help you keep track of your cat’s weight:

  • Start weighing your cat regularly. Take note of any unplanned weight loss.
  • Monitor your cat’s appetite. See whether something has changed.
  • Please make a note of any changes that could upset your cat or stress them out.
  • Pay attention to your cat’s behavior. Check to see if they are acting differently than usual.

These are all essential criteria to follow if you believe your cat has lost weight. If the weight loss is unintentional, you will need to determine the cause and treat it.

When in Doubt, Contact Your Vet

Watching your cat’s weight will help safeguard their physical health. If you see that your cat has been eating, but they are still losing weight, this can cause concern. Unintended weight loss could signify a medical condition. Make sure that your fur baby sees your veterinarian immediately if there is unexplained weight loss.

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Located just a stone’s throw away from beautiful Lake Zurich, Companion Animal Hospital, formerly Lake Zurich Animal Hospital, has warmly welcomed pets and their families since 1973.