Common Cat Illnesses by Age

Here is the fact that changes how you look after a cat: illness in cats is strongly patterned by age, and the pattern is predictable enough to screen for. Kittens get infections. Young adults get injured, blocked and fat. Cats from about seven get the slow internal diseases — kidney, thyroid, diabetes, dental — and cats past ten get those plus arthritis and cancer. That means the same vague symptom carries different odds at different ages. A three-year-old who is drinking more is unusual; a thirteen-year-old who is drinking more has a short and specific list of likely causes. This page walks through each life stage, what actually turns up, and what catches it early. If you are not sure which stage your cat is in, the free cat age calculator will tell you in seconds.

Why Age Changes the Odds So Much

The same symptom means different things at different ages, and that is genuinely useful.

Young cats meet the world; old cats wear out. A kitten’s immune system is still learning, so infections dominate. A young adult roams, fights and eats too much, so trauma and weight problems dominate. From middle age onwards, the failures are internal and gradual — organs that have done a decade of work.

Cats hide all of it. A cat is a small predator that is also prey, so concealing weakness is hard-wired. That is why the internal diseases of middle age are usually caught by a blood test rather than by an owner spotting something. There is more on the warning signs owners miss if you want the symptom-by-symptom version.

Screening is the whole game after seven. The four big mature-cat diseases are all detectable well before symptoms appear, and all four are managed better when caught early. That is the entire argument for annual bloods from seven and six-monthly checks from eleven.

Indoor and outdoor lives split the risks. An outdoor cat carries far more infection and trauma risk at every age. An indoor cat carries more weight-related risk. Neither is immune to the age-linked internal diseases.

Kittens: Birth to Six Months

Kittens are robust until suddenly they are not, and the gap between "a bit off" and "seriously ill" can be a few hours.

Cat flu is the classic. Sneezing, runny eyes, a snotty nose, sometimes mouth ulcers and a fever. It is usually viral (herpesvirus or calicivirus), it spreads easily in litters and shelters, and the danger is a blocked nose — a kitten who cannot smell her food stops eating.

Worms are near universal. Roundworms pass from the mother in milk, so assume every kitten has them. A pot belly, poor growth and visible spaghetti-like worms in stool or vomit are the giveaways. Worming starts at two weeks and repeats every two weeks until twelve weeks.

Fleas cause more than itching. A heavy flea burden can make a small kitten genuinely anemic. Pale gums and lethargy in a flea-covered kitten is an emergency, not a grooming problem.

Diarrhea matters more than in an adult. A kitten has almost no reserve. Loose stools for more than 24 hours, or any diarrhea with lethargy, needs a same-day call.

Panleukopenia is the one to fear, and the one vaccination prevents. Sudden vomiting, watery diarrhea, total collapse. It kills unvaccinated kittens quickly. The kitten vaccination schedule exists mainly for this and for cat flu.

Ringworm and ear mites round out the list. Both are common, both are treatable, and ringworm spreads to people — a circular patch of hair loss on a kitten deserves gloves and a vet visit.

Young Adults: One to Six Years

This is the healthiest stretch of a cat’s life, which is exactly why problems get missed.

Urinary problems dominate, especially in males. Feline lower urinary tract disease causes straining, frequent tiny wees, blood, and weeing outside the tray. In a male cat it can tip into a full blockage, which is fatal within about 24–48 hours untreated. A blocked bladder is one of the few true cat emergencies and it happens most in young, indoor, overweight, stressed males.

Fight wounds and abscesses. Outdoor cats get bitten. A bite seals over, then swells into a hot painful lump three to five days later, often with a fever and a cat who has gone quiet. Antibiotics and drainage sort it; ignoring it does not.

Weight creeps up from about two. Most cats reach adult size at around twelve months and then simply keep eating the same amount while doing less. Obesity is the single biggest driver of diabetes and arthritis later, and it is the most preventable thing on this whole page.

Dental disease starts earlier than owners expect. Red gum margins and a faint smell at three or four years old are the beginning of dental disease, which by middle age affects the majority of cats and hurts constantly.

Trauma is the leading cause of death in young outdoor cats. Road accidents especially. There is no screening for this one — only fencing, curfews, and honest thinking about the road you live on.

Mature Cats: Seven to Ten

Nothing dramatic happens here. That is the point.

Chronic kidney disease begins silently. Cats lose about two-thirds of kidney function before they show a single symptom, which is why the first sign — drinking more and producing bigger clumps in the tray — already means it is well established. Newer blood tests (SDMA) flag it earlier than the older ones. Kidney disease in cats is managed with diet and medication for years, not weeks.

An overactive thyroid usually starts after eight. The picture is memorable: a cat losing weight while eating ravenously, often restless, vocal at night, with a scruffy coat and sometimes vomiting. Hyperthyroidism is very treatable, including a curative option.

Diabetes shows up in the overweight. Drinking a lot, weeing a lot, losing weight despite a good appetite. Caught early, some cats go into remission on the right diet and insulin, which is a genuinely underappreciated fact — see diabetes in cats.

Dental disease reaches its peak. Bad breath, chewing on one side, dropping food, and painful resorptive lesions that dissolve the tooth from within. Cats almost never stop eating because of it, so the absence of a symptom proves nothing.

Lumps deserve measuring. Any new lump that is growing, firm or attached to the tissue underneath needs a needle sample. Mammary lumps in unspayed females are especially serious in cats and are usually malignant.

Senior and Geriatric: Eleven and Over

Expect more than one problem at once — that is the defining feature of this stage.

Arthritis is nearly universal and nearly invisible. X-ray studies of cats over twelve find joint changes in the large majority of them, yet most owners report no limping. Cats do not limp because both sides hurt equally. Instead they stop jumping, take stairs one at a time, sleep lower down, and go beside a high-sided tray.

Kidney disease becomes common. By the mid-teens a large share of cats have some degree of it. Weight loss, poor coat, drinking more, and later vomiting and mouth ulcers.

High blood pressure rides along with kidney and thyroid disease. It can cause sudden blindness — a cat bumping into things with wide, staring pupils needs checking that day, because rapid treatment sometimes restores sight.

Cancer risk climbs. Lymphoma is the most common feline cancer, often showing as weight loss, vomiting or diarrhea that does not resolve.

Cognitive dysfunction appears past about fifteen. Loud yowling at 3am in an empty hallway, staring at walls, forgetting where the tray is, disrupted sleep. It is manageable with routine, night lights and sometimes medication.

Weight loss is the master signal. In a cat over ten, losing weight without trying is the single most useful early warning there is. Weigh her monthly on kitchen scales in a carrier and note the number.

The Whole Picture at a Glance

Age bands are approximate — an indoor mixed-breed cat of nine and a Maine Coon of nine may sit in different places.

What "Off" Actually Looks Like in a Cat

Owners say "she is just not herself" because cats give you so little. Here is what that phrase usually means in practice.

She has changed where she sleeps. Lower, more hidden, more often. A cat who abandons her high perch has usually stopped being able to reach it comfortably.

Her coat has changed texture. Greasy, clumped or dandruffy along the back means she has stopped grooming — that area is the hardest to reach with a sore spine.

Her eating pattern shifted, not stopped. Slower eating, chewing on one side, dropping bits, going to the bowl and leaving, or wanting only soft food. All of that points at teeth or nausea long before appetite disappears.

Her tray output changed. Bigger wet clumps mean more urine, which means kidney disease, thyroid or diabetes until proven otherwise. Smaller, more frequent ones mean bladder trouble.

She greets you differently. Less coming to the door, less rubbing, more sitting apart. Sociability is expensive for a cat who feels rough.

She has got quietly thinner. Feel the spine and hips. If the bones have got sharper since the summer, that is data — and in an older cat it is the most reliable early signal you have.

Screening: What to Ask For and When

None of this is exotic, and most of it is cheap relative to treating the same disease late.

Under one year: the vaccination course, regular worming and flea treatment, a weight check at every visit, and neutering at the age your vet advises.

One to six years: an annual exam with a proper mouth check and a weight recorded each time. Ask for the weight to be read out and written down; a 1 lb (0.45 kg) gain on a 10 lb (4.5 kg) cat is a 10% change.

From seven: annual blood and urine testing. Ask specifically for kidney values including SDMA, a thyroid level, blood glucose, and a urine specific gravity — the urine test is the one most often skipped and it is the one that catches kidney disease earliest.

From eleven: the same twice a year, plus blood pressure, and an honest conversation about mobility. Ask about a trial of pain relief if she has stopped jumping.

At any age: weigh her at home. Stand on bathroom scales holding her, subtract your own weight, or put the carrier on kitchen scales. Monthly is plenty, and the trend is what matters.

When to Call Your vet

Age changes the odds, but it does not change the emergencies.

Go now, any age: straining in the tray with nothing produced, open-mouthed or labored breathing, collapse, sudden back-leg weakness with crying, a seizure, pale or blue gums, suspected poisoning, or a road accident even if she looks fine.

Same day: no food for 24 hours in an adult or 12 hours in a kitten, repeated vomiting, blood in urine or stool, sudden blindness or wide fixed pupils, a hot painful swelling, or severe lethargy.

This week: gradual weight loss, drinking noticeably more, a coat that has gone unkempt, bad breath, reduced jumping, a new lump, or night-time yowling in an older cat.

Never withhold food to see what happens. Cats develop fatty liver disease (hepatic lipidosis) quickly when they stop eating, so a hunger strike makes any underlying illness worse rather than clarifying it.

Frequently Asked Questions

At what age do cats start getting health problems?

The slow internal diseases — kidney disease, overactive thyroid, diabetes and significant dental disease — typically begin between seven and ten years old, usually with no symptoms at first. Before seven, most problems are injuries, urinary trouble and weight gain rather than organ disease.

What is the most common illness in older cats?

Chronic kidney disease and dental disease are the two most frequently diagnosed conditions in cats over ten, with an overactive thyroid close behind. Arthritis is probably the most common of all, but it is heavily under-diagnosed because cats stop jumping rather than limping.

How often should an older cat see a vet?

Cats aged seven to ten should have an annual examination with blood and urine testing. From eleven, most vets recommend every six months, adding blood pressure checks. Twice-yearly visits catch changes between appointments that a single annual visit would miss entirely.

Why do cats hide illness so well?

Cats are both predator and prey, and an animal that visibly limps or lies exposed advertises itself as an easy target. Concealing weakness is hard-wired and domestication has not removed it, which is why blood tests find disease long before owners notice symptoms.

What are the first signs of kidney disease in a cat?

Drinking more water and producing noticeably larger clumps in the litter box are usually first, followed by gradual weight loss and a coat that looks unkempt. By the time these appear, roughly two-thirds of kidney function is already lost, so blood testing from age seven matters.

Does my indoor cat still need annual check-ups?

Yes. Indoor living reduces infectious disease and trauma risk, but it does not reduce kidney disease, thyroid disease, dental disease, arthritis or cancer at all — and indoor cats are more likely to be overweight, which raises diabetes and joint risk.

The practical value of an age-based view is that it tells you what to look for and when to spend money on testing. Kittens need vaccination, worming and a fast response to anything off. Young adults need a healthy weight and a watchful eye on the litter box. From seven, ask for annual blood and urine tests even though she looks fine, because that is exactly the stage where kidney, thyroid and dental disease start quietly. From eleven, make it twice a year and start weighing her at home, because unexplained weight loss in an older cat is the most useful early warning you will get. Check her life stage with the free cat age calculator before your next appointment, and take her weight history with you.