Common Illnesses & Symptoms in Cats
Cats are brilliant at hiding when something is wrong. It's an instinct — in the wild, showing weakness is dangerous. Which means that by the time your cat is clearly unwell, they may have been feeling off for a while. Knowing what to look for makes all the difference.
Here are the most common illnesses cats face, what the signs and symptoms look like, and when to get to the vet.
Dental Disease & Gum Disease
Research by the Royal Veterinary College found that gum disease and dental disease are the most common conditions diagnosed in cats across the UK — affecting over 15% of cats for gum disease alone. Most cats show no obvious signs until the disease is advanced, which is why regular dental checks at routine vet visits are so important.
Signs to watch for: bad breath, drooling, difficulty eating, pawing at the mouth, dropping food, or a reluctance to let you touch their face. Left untreated, dental disease causes significant pain and can affect the kidneys, heart and liver. Treatment ranges from professional dental cleaning under anaesthetic to tooth extraction in more severe cases.
Cat Flu (Upper Respiratory Infections)
Over 90% of upper respiratory infections in cats are caused by feline herpesvirus or feline calicivirus. Symptoms are similar to a human cold — sneezing, watery eyes, nasal discharge, congestion and a reduced appetite. Once infected with herpesvirus, a cat becomes a lifelong carrier, with stress often triggering flare-ups.
Mild cases in healthy adult cats may clear up within seven to fourteen days with supportive care — keeping them warm, encouraging eating and drinking, and keeping their eyes and nose clear. However, kittens, elderly cats and immunocompromised cats are at much higher risk of serious complications and should be seen by a vet at the first sign of illness. Vaccination significantly reduces both the risk and severity of cat flu.
Chronic Kidney Disease (CKD)
Chronic kidney disease is one of the leading causes of serious illness in cats, particularly in older animals. The kidneys gradually lose their ability to filter waste from the blood, and because cats are so good at compensating, the disease often goes undetected until it has progressed significantly.
Signs to watch for: increased thirst, increased urination, weight loss, reduced appetite, lethargy and vomiting. If you notice your cat drinking noticeably more than usual, this is always worth a vet visit. If detected and treated early, the progression of the disease can be slowed, quality of life improved and life expectancy increased. Treatment typically involves a specialist renal diet, medication and regular monitoring.
Hyperthyroidism
The most common signs of hyperthyroidism — an overactive thyroid gland — are weight loss despite an increased appetite, along with increased thirst and urination. Affected cats may also show vomiting, diarrhoea, hyperactivity and an unkempt or greasy coat. It's one of the most common conditions in older cats and is very treatable once diagnosed — through medication, surgery or a specialist diet. If your older cat seems to be losing weight but eating well, get them checked.
Diabetes
Feline diabetes is increasingly common, particularly in overweight or older cats. The pancreas either stops producing enough insulin or the body stops responding to it, leading to high blood sugar. Signs include increased thirst, increased urination, weight loss despite a good appetite, and in more advanced cases, weakness in the hind legs. Treatment is focused on management rather than cure and typically includes insulin injections alongside dietary changes. With the right care, diabetic cats can live long and comfortable lives.
Obesity
It's estimated that roughly half of UK cats are overweight or obese, and being overweight significantly increases the risk of joint problems, diabetes, heart disease, certain cancers and bladder stones. Obesity is one of the most common and most preventable health issues cats face. If you're not sure whether your cat is a healthy weight, your vet can assess their body condition score at any routine appointment.
Feline Lower Urinary Tract Disease (FLUTD)
FLUTD is a collective term for conditions affecting the bladder and urethra. Cystitis — inflammation of the bladder — is common and is more often caused by stress, bladder crystals or stones than by infection. Signs include straining to urinate, frequent visits to the litter tray with little result, blood in the urine, or urinating outside the litter tray. In male cats, a blocked urethra is a veterinary emergency — if your male cat is straining without producing urine, get to a vet immediately.
Signs that always need a vet
Cats mask illness well, so trust your instincts. If something feels off, it probably is. These signs always warrant a prompt vet visit:
— Not eating for more than 24 hours
— Significant increase in thirst or urination
— Unexplained weight loss
— Lethargy or hiding more than usual
— Vomiting or diarrhoea lasting more than 24 hours
— Straining in the litter tray
— Any breathing difficulty
— Pale, white or yellow gums
— Sudden collapse or loss of coordination
And if your cat shows any of these signs — get to a vet the same day, or an emergency vet out of hours. Don't wait to see if it improves.
The best thing you can do
Get to know your cat's normal. Their usual appetite, thirst, litter habits, energy levels and weight. When you know what's normal for your cat, you'll spot when something changes — and that early awareness is often what makes the difference between a straightforward treatment and a much more serious situation.
Annual vet checks are invaluable — even for cats who seem perfectly well. Many conditions, including dental disease, kidney disease and hyperthyroidism, are picked up at routine health checks long before any symptoms appear.