Cats hide illness better than almost any animal people keep, and the household that knows what a healthy cat looks like detects disease years earlier than the one waiting for a symptom to announce itself. For Cats (Felis catus), a species whose survival strategy is silence about weakness, the health topic runs on three skills: knowing the individual cat's baselines, recognizing the drift that means illness, and knowing which signs cross the line into emergency care.
The baselines that matter
Every health judgment starts with the individual's normal: appetite and its speed, daily water intake, energy across the day, sleep hours, grooming thoroughness, litter box output, and the weight that the monthly scale check converts into numbers. Rectal temperature in a healthy cat runs 100.5 to 102.5 degrees Fahrenheit (38.1 to 39.2 degrees Celsius), the resting heart rate is fast for a household animal at 140 to 220 beats per minute, and respiration at rest sits between 20 and 30 breaths per minute; the sleeping respiratory count, like the dog's, is the early number in heart disease. Gums are pink and moist, and the coat is groomed to its full shine, because grooming stops are among the first visible signs of sickness.
The litter box is the cat's most detailed health report, and it is checked daily: urine clumps in their usual number and size, stool in its usual form, no straining, no blood, no missing visits. Cats that use the box quietly and completely are reporting normal urinary and digestive function, and any change in that report, more clumps, bigger clumps, no clumps, earns a closer look before it earns a behavior label.
The drift: how cats show illness
Sick cats hide, eat less, groom less, and move less, and each of those is a symptom rather than a mood. The appetite that fades for two meals, the cat that skips its morning lap, the coat that loses its shine across weeks, the water bowl that empties faster or slower than usual, and the hiding that stretches from an hour to a day are the classic drifts. Increased drinking is the signature early flag of kidney disease, hyperthyroidism, and diabetes, three of the most common conditions of middle and old age, and it is measurable in the bowl and visible in the box.
Behavior completes the picture: the social cat that withdraws, the grumpy cat whose grumpiness is new, the cat that stops jumping to its favorite perch because the joints or the belly hurt. Pain in cats presents as absence, the jump not taken, the play not joined, and the household that logs these absences with dates gives its veterinarian a history worth a dozen guesses. Any drift persisting past a couple of days, or any drift that arrives with weight change, is an appointment rather than a wait.
The toxins cats meet indoors
The indoor cat's poisoning list is shorter than the dog's and more lethal per item. Lilies lead it: a bite of petal, a lick of pollen, or the water from a lily vase causes acute kidney failure in cats, which is why the flower is banned from cat households entirely rather than placed high. Human medications follow, with acetaminophen fatal at a fraction of a tablet because the feline liver cannot clear it, and ibuprofen damaging kidneys and gut; the permethrin spot-on flea products packaged for dogs cause tremors and seizures when applied to or licked by a cat. Onions and garlic damage red blood cells, the lily-relative and the unknown-plant calls go to the poison hotline, and the liquid potpourris and essential oils that smell harmless cause burns and liver injury in the species that walks across the puddle and licks its paws. The household that cat-proofs its shelves and buys its flowers from the safe list has removed most of this risk before the cat ever meets it.
Signs that need urgent care
Some signs skip the waiting room entirely. The male cat that enters the litter box repeatedly, strains, and produces nothing is obstructed, a blockage that becomes fatal within a day and announces itself as the crying-in-the-box emergency that every male cat household learns to fear. Difficulty breathing, open-mouth breathing, which is always abnormal in a cat at rest, blue or pale gums, collapse, a seizure, suspected poisoning, and the sudden inability to use the hind legs, the painful aortic clot that accompanies heart disease, all require immediate care with no observation period.
Vomiting has its own ladder: a single episode in a bright cat that asks for dinner is watched; repeated vomiting, blood in the vomit, or vomiting with lethargy is a same-day visit; and the cat that vomits and cannot stop, or that retches without producing anything, belongs in the car. Trauma from falls or vehicles warrants imaging even when the cat walks, because cats hide internal bleeding as effectively as they hide everything else. Heatstroke, the heavy panting open-mouthed cat on a hot day, is treated with cooling and immediate transport.
Conditions that commonly affect cats
Chronic kidney disease leads the feline disease list in middle and senior age, progressing slowly and caught early by the bloodwork and urinalysis that the senior calendar runs twice yearly. Hyperthyroidism follows, the overactive thyroid of older cats that drives weight loss despite ravenous appetite, and diabetes completes the endocrine trio, arriving alongside the obesity the diet chapter works to prevent. Dental disease affects most cats by their middle years, from gingivitis to the tooth resorption lesions unique to the species, and the mouth that hurts changes appetite before it changes anything visible.
The infectious diseases the vaccine calendar prevents, panleukopenia and the respiratory viruses, and the feline leukemia and immunodeficiency viruses that testing screens for, are rarer in vaccinated indoor cats but remain the reason the calendar exists. Asthma shows up as the coughing and wheezing that owners mistake for hairballs; heart disease, hypertrophic cardiomyopathy foremost, hides until the breathing changes; and the urinary inflammation of feline idiopathic cystitis, stress-linked and recurrent, connects the litter box report to the stress chapter. None of these conditions is a mystery to the household that keeps records, because each one writes its early chapters in the log.
The FeLV and FIV tests, explained
Two retroviruses define the testing layer of feline medicine, and both are screened with a quick clinic blood test. Feline leukemia virus, FeLV, spreads through close contact and saliva, and the infection that persists shortens life through anemia, cancers, and immune failure, which is why kittens are tested before joining a household and why the FeLV vaccine protects the cats whose risks run outdoors. Feline immunodeficiency virus, FIV, spreads through bite wounds, lives quietly for years in many cats, and its positive test deserves a second confirmation, because the managed FIV-positive cat can live a near-normal lifespan indoors alongside calm companions. Both tests inform the household's introduction plans, the multi-cat arithmetic, and the veterinary calendar, and both are the reason the new cat's first vet visit happens before the first nose-to-nose meeting.
The senior values, named
The senior bloodwork screen earns its paragraphs because its values are the early biography of the three big feline diseases. Creatinine and the urine concentration measure the kidneys, which decline silently for years; the total thyroxine measures the thyroid, whose excess drives weight loss with appetite intact; and the blood glucose measures the diabetes that obesity feeds, with the fructosamine test confirming what a stressed clinic visit muddies. Blood pressure joins the panel because hypertension rides with kidney and thyroid disease and silently damages the retinas it can detach. Each value is read against the previous visit's, because the trend catches the disease at the stage where prescription diets and medication change its course, and the twice-yearly cadence exists exactly because these curves move fast in feline years.
The health routine
The routine that catches feline disease early is short: the monthly weigh-in, the daily litter box glance, the weekly hands-on survey of coat and body, and the veterinary calendar that runs annually for adults and twice-yearly for seniors with bloodwork and thyroid and kidney values. Cats need the same preventive structure as dogs, vaccination, parasite prevention, dental care, and the examinations that find the drifts early, with the special feline additions of leukemia testing and the indoor-outdoor conversation. The household that runs this routine is not being anxious; it is compensating for a species that would rather die quietly than complain, and the records it keeps are the voice the cat will not use. The cat that is weighed monthly, watched daily, and examined on schedule is the patient most feline diseases can still be caught in time to treat, and the household that runs the routine will spend its veterinary budget on prevention rather than crisis, which is the cheaper of the two by every measure that matters, and the earlier the drift is read, the shorter the treatment and the longer the comfortable years that follow.