Feline weight loss, when unplanned, is something to be concerned about at any age. Unfortunately, a cat losing weight is often a sick cat, and this key cat illness symptom is easy for many pet parents to miss. Your cat, when healthy, will normally weigh the same year after year, except for those who gain weight. Good feline care includes knowing what a normal cat weight is for your feline and taking action when any cat weight loss occurs. Many cat illnesses have weight loss as one of the primary symptoms.

I have examined thousands of cats over the last 20 years and I have seen healthy cats come in year after year weighing the same, almost to the ounce. There are two exceptions to that: (1) the cats that steadily gain weight and become overweight, and (2) cats that have an illness.

Unfortunately, there are many, many misconceptions about cat weight problems. For instance, many believe that weight loss is a good sign, especially with the pet obesity epidemic. Also, many believe that a cat losing weight is a normal occurrence with age or is acceptable in small amounts, regardless of whether it is happening quickly or gradually over time. However, as you will learn throughout this article, these things are often not true.

Debunking Cat Weight GAIN Myths

Cat weight gain is cause for concern, but not because it indicates an illness. There is no disease in cats that causes weight gain. You may have read or heard otherwise, but this is simply not true. I have seen misinformation in various places over the years about this subject.

For example, I have heard it said that cats gain weight because they are hypothyroid. Cats do not get hypothyroidism except in one type of situation. If a hyperthyroid cat has his thyroid glands surgically removed or has radioactive iodine treatment for feline hyperthyroidism, then it is possible that after the removal, the cat's thyroid levels may be low, either temporarily or permanently. However that is a man-made condition. Naturally occurring hypothyroidism, if it does exist, is so rare that your chances of having a cat with that condition are pretty much nil.

The other time I have heard a disease blamed for a cat being overweight is in association with diabetes. I have heard it said that diabetes makes cats fat. That is not true. Fat cats are more likely to get diabetes which will then make them lose weight if not treated quickly, but diabetes does not make them fat.

If your cat is overweight, he is eating too much. Period.

Debunking Myths about a Cat Losing Weight

Unlike weight gain, which happens because of poor diet or portion control, there are many actual illnesses and diseases that cause feline weight loss. Because cats tend to stay the same weight year after year or they gain weight, it is ALWAYS of concern if you notice your cat losing weight.

There are some myths associated with feline weight loss as well. I have been asked or told many times by cat owners that their cat's weight loss must be due to growing older. Wrong! Old age is not a disease! Old age does not cause feline weight loss, but old age can increase your cat's risk of acquiring certain feline diseases or a number of problems that cause this illness symptom. But the age itself is not a reason for weight loss.

A major problem with feline weight loss is our inability to see that it is happening until a significant decrease in the weight has occurred. For example, a 10 pound cat can lose a pound and it may very well not be noticed by the owner. A pound is nothing, you say? Maybe to us. But a pound weight loss in a 10 pound cat is loss of 10% of the cat's body weight. That is significant.

Too often, I have seen cats brought in for an examination only after they look like the cat to the left and this is MUCH too late!

Unfortunately, when you look at your cat, you may not notice early weight loss. That first pound lost is not easy to see if your cat has been at a healthy weight for years.

In an ideal world of ideal cat care, every cat owner would own a pediatric or feline scale and weigh their cats regularly throughout their lives. If this is not an option, although it is the most accurate, every owner would weigh their cats while holding him in your arms and deducting your own weight from his on your regular human scale. Many conditions would be diagnosed earlier if we all did that, allowing for earlier treatment and a better outcome.

Feline weight loss is the symptom that worries me the most of any warning signs you may see at home. It is the one cat illness symptom that most often has something serious associated with it.

What are the Causes of Feline Weight Loss?

Anything and everything. Seriously. Cat weight loss can occur due to:

- hyperthyroidism in cats

- feline kidney disease

- cat diabetes

- feline leukemia and feline immunodeficiency virus (FIV)

- cancer

- feline inflammatory bowel disease

- upper respiratory infections

- cat dental problems

.....and on and on. There's almost nothing imaginable that can't cause weight loss in cats. If you explore our Feline Illnesses index, you will see that weight loss can be and often is a symptom in any condition.

This is another reason feline weight loss is a problem. Not only is it not obvious until too much weight has been lost, but it is so nonspecific as to the cause. One can never say, "my cat lost weight so she has diabetes" or "my cat lost weight so she has dental problems". There are so many causes that only a good history and physical exam by your veterinarian can narrow the possibilities and even then, blood work is often necessary, as can be more advanced radiography studies.

Solving the Mystery of Your Cat Losing Weight

At the bottom of this page, you will see a large sampling of questions and answers from visitors just like you who are wondering what might be the cause of the feline weight loss they were observing. You may even find someone in exactly the same situation as you!

The following question, though, illustrates just how broad and vague these symptoms may be and how difficult it can be to diagnose. Abnormal cat weight loss can affect a cat of any age and any gender, and Erica's question is a perfect illustration of this.

Erica wrote:"I have a one year old male cat. About 3 months ago he started drooling, lost body weight, and was irritable towards the other animals in the house. The symptoms keep coming and going. But he has not gained all his body weight back. Had blood test done at the vet and they said his liver results were a little high but not out of the normal range. He likes to roll in dirt outside when he feels bad. He is normally an inside cat."

My answer: Feline weight loss at any age is cause for concern. If kittens and young cats lose weight, we become especially concerned. Drooling is also abnormal and his irritability could be significant if it never occurred before and now is an intermittent event.

There are a few things that come to mind if I look at all his symptoms together:

(1) Problems in the mouth. Were his teeth and gums examined very carefully, all the way back to his throat? Was his tongue closely examined, including the area under the tongue? Was there excessive gingivitis or any ulcers? Do his teeth need a professional cleaning? Are there any abnormal masses in the mouth? Any painful areas?

(2) Toxins. Is there anything he can get into from time to time that is poisonous to him? Any plants, grasses, medications, rat poison, anti-freeze, cleaning supplies, construction materials? Does he lick anything indoors or outdoors on a regular basis? Even if a plant or grass is not truly poisonous, all can be irritating to the mouth and stomach of a cat.

(3) Blood work was mentioned, but I don't know if it included testing for Feline Leukemia Virus and Feline Immunodeficiency Virus. If not, that testing should be performed. Cats with those viruses frequently have mouth problems and have feline weight loss. He's young and has spent at least some time outdoors so he certainly has been at risk for acquiring those viruses.

Those are the top problems that come to mind with the symptoms described. Of course, other illnesses can cause those symptoms: kidney disease, other viruses, liver disease and others. However, his symptoms and his age and the blood results so far put these other things at the bottom of the list of possibilities right now for me. Also, of course, make sure he is eating a good quality, nutritious cat diet.

Recommendations then include a very complete oral exam, under sedation if necessary, and perhaps a second opinion. I also recommend FeLV and FIV testing if that wasn't done or was done over 3 to 4 months ago. In addition, think hard and look around carefully to see if there is anything that could possibly be toxic to a cat.

If none of these procedures come up with a cause and he still is too thin or losing weight and drooling, I would proceed to X-rays of his chest and abdomen.

For more examples of feline weight loss questions and answers, please see the submissions at the bottom of this page. And remember, if your cat is losing weight, it's time for a trip to the veterinarian!

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