Cats have an evolutionary tendency to conceal signs of illness -- in the wild, appearing weak is a vulnerability. For domestic cat owners, this means health problems can quietly develop for some time before obvious signs appear. Understanding the most common conditions and their early signals gives you a better chance of catching issues while they are still highly manageable.
This guide covers the health problems most frequently seen in cats across veterinary practice, the practical signs to watch for at home, and when each situation calls for a vet visit.
Dental disease is one of the most common conditions in cats, with veterinary estimates suggesting that the majority of cats over three years old have some degree of periodontal disease. Like dogs, cats rarely show obvious pain from dental problems and typically continue eating even with significant disease present -- which is one reason it advances so far before owners notice.
Signs include noticeably bad breath (beyond a cat's normal breath), yellow or brown tartar especially visible on the upper back teeth, red or swollen gums, drooling, reluctance to eat hard food, or pawing at the mouth. Annual dental check-ups and professional veterinary dental cleanings when appropriate are the standard approach. Daily toothbrushing with cat-safe toothpaste is highly effective at slowing tartar accumulation, though it requires patient training -- the Cornell Feline Health Center recommends starting tooth-brushing habits as early in a cat's life as possible.
Obesity is prevalent in domestic cats, particularly indoor, sedentary adults and cats fed primarily dry food ad libitum. Excess weight in cats is associated with diabetes, joint disease, urinary problems, and a significantly shortened lifespan. It can also make cats more susceptible to a serious liver condition called hepatic lipidosis if they go off food for any reason.
A cat at a healthy weight should have ribs that are easily palpable with light pressure, a visible waist behind the ribcage when viewed from above, and an abdominal tuck visible from the side. The normal 'primordial pouch' -- a loose skin flap on the lower belly -- is present in healthy cats of any weight and should not be confused with fat accumulation. Weight management in cats must be done gradually and ideally under veterinary guidance; rapid calorie restriction risks triggering hepatic lipidosis.
Chronic kidney disease (CKD) is among the most common conditions in older cats, with prevalence estimates from veterinary sources rising substantially in cats over 10-12 years. The kidneys' role in filtering waste and regulating fluid balance means that as function declines, early signs often relate to hydration and appetite.
Early signs of CKD can be subtle: increased thirst and urination (as the kidneys lose concentrating ability), gradual weight loss, reduced appetite, and a slightly dull coat. In more advanced disease, vomiting, lethargy, and bad breath with an ammonia-like quality become more prominent. Because early CKD is often symptom-light, regular veterinary blood and urine testing in cats over 7-8 years is an important screening tool -- the condition is not curable, but progression can be slowed considerably with appropriate dietary and medical management when diagnosed early.
Feline lower urinary tract disease (FLUTD) is a broad term covering conditions affecting the bladder and urethra -- including feline idiopathic cystitis, bladder stones, and urethral obstruction. It is particularly common in male cats, indoor cats, and cats on dry-only diets. Signs include straining to urinate, frequent trips to the litter box with little or no urine produced, blood in the urine, crying in the litter box, and excessive licking of the genital area.
Urethral obstruction -- where the urethra becomes completely blocked -- is a life-threatening emergency that is more common in male cats due to their narrower urethra. A male cat who is straining in the litter box and producing no urine at all requires emergency veterinary care immediately. Increasing moisture intake (through wet food and drinking water) is one of the most broadly recommended strategies for reducing FLUTD recurrence.
Hyperthyroidism -- an overactive thyroid gland producing excessive thyroid hormone -- is one of the most common hormonal conditions in older cats, with most cases occurring in cats over 10 years. Increased thyroid hormone raises metabolic rate, and the classic signs reflect this: weight loss despite a normal or increased appetite, increased activity or restlessness, increased thirst and urination, vomiting, and a coat that appears unkempt.
Hyperthyroidism is highly treatable with medication, dietary management, radioactive iodine therapy, or surgery -- but it is easily missed because the early signs (a cat eating well and seeming more 'lively') can seem positive at first glance rather than concerning. A gradual, unexplained weight loss in a senior cat that is eating well is one of the clearest indicators to ask your vet about thyroid function testing.
The most dangerous misconception about cat health is that a cat who is still eating is essentially fine. Many serious conditions in cats -- kidney disease, dental disease, hyperthyroidism, early diabetes -- progress while the cat continues eating relatively normally. Changes in weight, drinking, litter box habits, and coat condition are often more reliable early signals than appetite alone.
Another common mistake is attributing weight loss in a senior cat to 'normal ageing.' While some lean muscle loss is a natural part of ageing, significant or accelerating weight loss is nearly always a signal of an underlying condition -- hyperthyroidism, CKD, dental disease, or cancer among the most common -- that deserves investigation rather than acceptance.
Finally, many owners avoid vet visits for cats because cats are difficult to transport and visibly stressed by the process. While cat stress at the vet is real, the consequence of delayed diagnosis in cats -- who hide illness until it is advanced -- means regular wellness visits are even more important for cats than for pets who show symptoms more readily.
For any cat, schedule a vet visit if you notice: unexplained weight loss or gain over a few weeks, a significant change in drinking or urination habits, straining in the litter box (especially with little or no urine output), persistent vomiting or diarrhoea, a noticeable decrease in activity or grooming, bad breath, or any sudden behavioural change. In senior cats (roughly 10 years and older), twice-yearly wellness exams -- rather than the annual standard for younger adults -- are a widely supported approach given how quickly age-related conditions can develop.
For urethral obstruction in male cats (straining with no urine production), do not wait -- contact an emergency vet immediately.
Chronic kidney disease, hyperthyroidism, dental disease, obesity, arthritis, and diabetes are among the most common conditions in cats over 10 years. Regular wellness bloodwork and urine testing -- typically twice yearly for senior cats -- is the most practical way to catch these conditions before symptoms become severe.
Increased thirst in cats (along with increased urination) is a notable clinical sign worth taking seriously. Common causes include kidney disease, hyperthyroidism, and diabetes -- all of which are manageable when caught early. A vet visit with a urine sample and bloodwork is the appropriate next step.
Cats hide pain well. Signs include reduced activity, reluctance to jump up or down, changes in posture (hunching), reduced grooming, withdrawal from social interaction, changes in facial expression (a squinting or tense expression), and sometimes increased aggression when touched in a sore area. Any sustained behavioural change in a cat warrants a vet check.
Yes -- a complete urethral obstruction, where a male cat cannot pass any urine at all, is life-threatening and can be fatal within 24-48 hours without treatment. If your male cat is repeatedly straining in the litter box and producing little or no urine, contact an emergency vet immediately.