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

MARJORIE    International

2/19/2014 8:14:06 AM

What an absolutely brilliant website. Live in Ireland with my gorgeous 14 year old tabby called "Squeak". Hyperthyroidism is the diagnosis by my trusted vet. As a first step we are treating him with medication for two weeks, after which my vet will assess progress. I will do anything that is 'humanely' possible to give Squeak the best chance of as good a quality of life as is possible. I will take each day at a time now and will continue to love and care for him with all my heart.

Teresa    San Bernardino, CA

10/23/2013 10:56:16 AM

Very helpful thank you

Janet    International

7/3/2013 11:26:07 AM

Very helpful thank you as my cat of 16 has very similar ailments. even though after many vet visits he still hasn't improved. so will be changing vet soon. he eats constantly.. always seems starving and gobbles he's good in such a hurry...lost so much weight.. vomits and has diarrhea. has been like this for over 6months. i noticed recently that he's making a sort of sound when he chews... so need to check he's jawline for any injuries and any tooth decay as this can lead to the problem of liver and kidney failure :( he has been diagnosed through a blood test that he is cancer free and no diabetes but really need a second opinion as has what has been subscribed for him in drugs have not the slightest done him any favours. we are back to square one :(

Cathy    NYC, NY

9/5/2012 10:37:00 PM

Thank you very much 4 this info. I've been worried about my cat & knew some weight loss occurs as all cats age, but, that this was different. I think this bad news but, i'd rather know than not know

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