My 15-Year-Old Cat Is Losing Weight

CatChannel veterinary expert, Arnold Plotnick, DVM, explains that weight loss in senior cats with good appetites could be a sign of hyperthyroidism and other diseases.

By Arnold Plotnick, DVM | Posted: September 12, 2008 3 a.m. EDT

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Q: We have a 15-year-old cat that has been losing weight for a few weeks now. He doesn't eat dry food as much as he used to, so we have been feeding him wet food. He eats as much as he likes, but he still seems to be losing weight. He is doing the same things he used to do (drinking the same amount of water, going potty in his litterbox, playing with our other cat, etc.). Is this normal for a cat this age to be losing weight?

A: Weight loss despite a normal or exceptionally good appetite is often a sign of illness, the most common one being hyperthyroidism. This is a condition in which the thyroid gland in the neck produces excessive amounts of thyroid hormone. Other clinical signs, such as increased water consumption, vomiting, diarrhea, restlessness, etc., may or may not be seen.

Diabetes is another illness in which cats lose weight despite an excellent appetite, however, most of these cats show a dramatic increase in thirst, and you report that your cat is drinking the same amount of water, so diabetes is lower down on my list.

Gastrointestinal cancer has to be considered in an older cat. Intestinal lymphoma is a common disorder in senior cats, with weight loss being the most prominent sign. While most cats with intestinal cancer show a decreased appetite, some cats show a normal or increased appetite; as cancer cells infiltrate the intestinal tract, absorption of nutrients across the intestinal wall may be impaired. The body acts as if it is starving, despite a normal appetite. The appetite might even increase, as some cats try to compensate for the decreased nutrient absorption.

You need to take your cat to your vet and have some blood tests performed, as well as a good physical exam.

Hyperthyroidism is usually easily diagnosed with a simple blood test, and is very treatable. In fact, it is curable.

Diabetes is treatable with diet and insulin.

Gastrointestinal cancer is a little more difficult to diagnose, requiring more advanced diagnostics such as abdominal ultrasound, endoscopy or surgery. Lymphoma, the most common cancer, is often responsive to chemotherapy. Low-grade lymphoma, a less aggressive form, actually has a pretty decent prognosis, with cats often living 18 to 24 months on oral medication. High-grade lymphoma usually responds to chemotherapy, but the length of remission is much shorter as compared to low-grade lymphoma.


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Reader Comments

Theresa    Portland, OR

11/19/2014 3:59:08 PM

I also have a 15-year-old kitty. He has a huge appetite and he eats all he wants but he continues to lose weight. It's not super rapid, but I think he's gone from 17 pounds to 13 pounds in about a year and a half. The vet did all the bloodwork tests, even the expensive thyroid test and xrays. Everything was normal and no tumors were found. I guess I have to believe it's just old age?

nell borda    Washington, DC

11/19/2014 6:26:54 AM

Thank you for this site & the information. My cat, similar to the cats with great appetites that want to eat constantly,is also losing weight. Vet suspects he has cancer.
So I'm just spoiling him, & letting him enjoy all he can.

Harvey    Bay Shore, NY

10/15/2014 10:11:22 AM

Great site and great info!! I would be concerned about putting a 15 year old cat on chemo for GI lymphoma bc of quality of life and suffering as I know this takes place in humans. Since I am not a vet or cat expert I would like to hear more thoughts on this... Thanks!!! Harvey

Marsha    Atascadero, CA

7/16/2014 8:52:23 PM

My 17 year old Maine Coon has gone from 16lbs to 8lbs 13oz in 7 months. I had a full senior health panel done and everything was normal. No change in eating/drinking/pooping/peeing. His activity level has decreased, most likely due to age, but he is still alert and social. I can only fear that it is cancer. My vet has suggested an ultrasound that would most likely determine that, but, treatment may only buy him a few more months,and unsure if he is he in any pain, he doesn't show any. It's a very heart breaking decision not to treat. I believe in quality of life (human and animal)So, until that fateful day, he will be pampered as he always has been, with great love knowing I was blessed he came into my life, as a stray

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