Kitty Korner: Aging Cats by Frank Utchen, DVM

First, how old is your cat, really? The system of assigning 7 cat years for each 1 year on our calendar is no longer considered accurate. The best way to calculate your cat’s age in human years is as follows: the first year of their life counts for 15 human years, the second year counts for 9 human years, and every year after that counts for 4 human years. So, for example, a 16 year old kitty is: 15 + 9 + (14 more years at 4 years each) = 80 in human years. The previous system would assign your kitty an age of 16 x 7 = 112. So your old girl or old boy is a lot younger than you thought! 

Nevertheless, as cats approach and pass the age of 10, various problems start popping up more frequently than in younger cats. Three of the most important are discussed below.  

Kidney Disease

Perhaps the most common medical problem faced by cats as they age is the onset of kidney failure. The kidneys make important hormones for the body, clean the blood, and determine how much water to keep in or filter out of the body. As a cat’s kidneys begin to fail—usually due to nothing other than age—they begin producing excess urine. The litter box for these cats will often be noticeably soaked. Cats typically do not drink much water; they will begin drinking more and more to keep up with the urinary water loss. Some cats begin to lose weight, eat less, and generally slow down. Of course, older cats often enjoy a relaxed pace of living anyway, so the slowing down may not be obvious. Simple blood and urine tests will help diagnose this condition. 

If an otherwise healthy-appearing cat is determined to be in the early stages of kidney failure, usually all that is recommended is a change in diet to a particular food designed for this condition, and the use of a medication called Calcitriol that helps protect the kidneys from further damage and helps cats feel better. As cats progress with this problem other medications may be helpful. Studies show that older cats diagnosed in kidney failure live an average of 277 days (about 9 months) when fed the proper food, yet live an average of 736 days (over 2 years) when given Calcitriol as well.


The thyroid gland is a small gland in the neck covered by the muscles adjacent to the larynx (“voice box”). This gland makes a hormone, tetraiodothyronine — otherwise just referred to as the “thyroid hormone” or as “T4”. In simple terms, this hormone sets the speed of one’s metabolism. The more hormone produced, the higher the metabolic rate. In cats whose thyroid gland becomes hyperactive, their metabolism speeds up. Those cats often have a high heart rate, dilated pupils, eat voraciously, and actually seem unusually hyper for an older cat. Most cats with this condition experience dramatic weight loss despite eating more because their metabolism is running so fast they burn up all the calories they eat, plus some.  

However, about 25% of hyperthyroid cats feel bad from the condition and become listless and inappetant. As with kidney failure, a simple blood test can determine if a cat is hyperthyroid. This condition can be treated either with oral medication given once or twice a day at home, or by receiving an injection of radioactive iodine which returns the thyroid gland to its normal rate of hormone production. In some instances surgery on the thyroid gland is appropriate. 


Sadly, cancer is as common in our companion animals as it is in humans. Cancer can strike any organ or body part, and when it occurs internally there are often no indications while in the early stages. A general decline in vitality may be all that is noticed, including a drop in appetite and activity level. Sometimes it is necessary to take X-rays, perform an ultrasound exam, perform endoscopy or laparoscopy (look inside with small fiberoptic scopes) or do blood tests to determine if cancer is present.

Some cancerous conditions can be effectively managed with minimal medications (e.g., bladder tumors or lymphoma—a kind of cancer of the lymph nodes and blood cells), although other types of cancer require surgery or may not be treatable in any case. The decision to treat or not treat a cat with cancer can be a difficult one, and no single answer is right for all cats and all families.   

At our practice we recommend any cat over 10 years old have a physical exam yearly, regardless of whether they are due for any immunizations and even if they never leave the house. Often, a general screening set of blood and urine tests is done to determine what a particular cat’s baseline levels are for the various tests so there is a reference point for future test results that may become abnormal.

Tags: aging, Frank Utchen, feline health, cats, kitty korner, kidney disease, cancer, hyperthyroidism

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