Common cat illnesses and how to know your cat is sick

Like any living creature, cats are vulnerable to illness. However, cats have a primal knack for hiding their pain and illness because in nature, this would make them susceptible to attack. If a prey animal appears injured or weak, it’s a matter of life and death, and cats have not yet learnt that in our homes, they are safe to show us they are sick so we can do something about it and help them.

In this article, we’ll explore the most common cat illnesses, the signs to look out for and what to do if your cat looks ill.

What are the most common cat health problems?

From hereditary illnesses, to parasites, viruses, skin allergies, tummy issues and dental problems, these are some of the most common cat health problems that veterinarians may see in our feline friends:

  • Chronic renal failure (CRF)
  • Feline lower urinary tract disease (FLUTD)
  • Flea allergy dermatitis
  • Dental disease
  • Heart disease (hypertrophic cardiomyopathy)
  • Arthritis
  • Gastrointestinal problems
    • vomiting (and hairballs)
    • diarrhoea (many causes)

Chronic renal failure

Chronic renal failure (CRF) is the most common genetic disease in domestic cats. The kidneys are a vital part of a cat’s waste processing and elimination function. They also reabsorb essential nutrients required by the cat’s body. There are many possible causes for kidney failure including genetic predisposition, kidney stones, dietary causes, autoimmune disorders and infectious causes. Unfortunately, clinical signs of renal disease will only show once more than 75% of renal function is affected. This means that often by the time renal failure is diagnosed, intensive treatment is required to save as much kidney function as possible.

Symptoms of chronic renal failure

The symptoms of CRF will generally show a kidney dysfunction or kidney failure, and will include signs like:

  • excessive urination
  • excessive thirst and drinking more water than usual
  • lack of appetite
  • vomiting
  • weight loss
  • lethargy
  • dull, dry skin and matted coat

How is CRF diagnosed?

The vet will start with diagnostic tests on the cat’s kidneys, which will include blood tests, urine tests and ultrasound. On X-rays and ultrasound, the kidneys may be enlarged and misshapen as a result of cysts; there may be visible stones in the renal pelvis, or evidence of fluid backing up in the kidneys. The urine tests will reveal the kidneys’ inability to efficiently filter waste materials, and may show the presence of proteins and other abnormal materials. All of these factors are analysed in conjunction to determine the severity of the disease and ultimately the prognosis for your pet.

How is CRF treated?

There is no cure for chronic renal failure, but the symptoms can be managed for the rest of the cat’s life. Each case will be managed based on the cause and severity of the disease – e.g. some cats develop anaemia (low red blood cell count) as the kidneys produce a hormone to tell the bone marrow to make red blood cells. As it is a progressive illness, the cat will need to be tested regularly and treatment adjusted to support their kidney function. A prescription kidney diet will also be necessary to help ease the burden of waste filtering on the kidneys.

Feline lower urinary tract disease (FLUTD)

Feline lower urinary tract disease (FLUTD) does not refer to a single condition, but rather a cluster of problems that affect a cat’s lower urinary tract. Whether there is inflammation in the bladder, the presence of bladder stones, an obstruction in the urethra, urinary tract infection, or even cancer, the symptoms can be frustratingly similar and there is seldom a single underlying cause that can be treated.

Symptoms of feline lower urinary tract disease (FLUTD)

The symptoms will first be noticeable in a cat’s changes in behaviour relating to urination:

  • difficulty producing urine; straining
  • only producing a small amount of urine at a time
  • painful urination (marked by crying or howling)
  • inappropriate urination (outside the litterbox, or in uncharacteristic places)
  • excessive licking or grooming of the genitals or abdomen
  • blood in the urine

How is feline lower urinary tract disease diagnosed?

If you notice your cat having trouble urinating, it’s important to get them to the vet as soon as possible. If they have a urethral obstruction and are not able to pass urine at all, this constitutes a medical emergency as it can be life threatening. The specific cause of a cat’s FLUTD is very difficult to diagnose, but the vet will thoroughly examine the cat, test their urine (urinalysis) and possibly use imaging to determine the presence of crystals and/or stones (uroliths) in the lower urinary system.

How is feline lower urinary tract disease treated?

Depending on the symptoms, the vet will treat each condition. For example: if bladder stones are causing an obstruction, the stones most likely require surgical removal; if there’s a urethral obstruction, the cat may need to be put under anaesthetic in order to place a catheter to remove the obstruction and void the bladder; feline idiopathic cystitis (FIC) or inflammation of the bladder not caused by bacteria is very difficult to diagnose and treat, and may have behavioural and stress-related causes. Managing your cat’s stress and allowing them to practise natural behaviours, while also ensuring persistent access to food, water and the litterbox without a territorial threat from other pets, can help with FIC and FLUTD in general.

FLUTD can be a recurring problem for many cats, so treatment and management may end up being a lifelong endeavour for cat owners. Specially formulated cat foods to support lower urinary tract health may reduce the recurrences of this condition.

Flea allergy dermatitis in cats

The causes and symptoms of flea allergy dermatitis are all in the name of this condition. When fleas bite, cats can be extremely sensitive to their saliva, which causes them to lick and scratch compulsively at the itch from the flea saliva. This compulsive scratching can injure their skin and even introduce bacteria, causing open sores and secondary infection. A cat can have a full allergic response from even one flea bite, so just because you have not seen any fleas on your cat does not rule out a flea bite allergy.

Symptoms of flea allergy dermatitis

While cats do groom themselves a lot, flea allergy dermatitis can cause relentless grooming to the point of self-injury. Symptoms include:

  • excessive grooming (licking and scratching)
  • inflamed, irritated or even broken skin
  • feline alopecia; patchy hair loss
  • ‘pimply’ or crusty-looking skin on the face and under the chin

How is flea allergy dermatitis diagnosed?

The veterinarian will do a physical examination of the cat, specifically looking for live fleas, flea dirt, and evidence of scratching and/or alopecia at the base of the cat’s tail.

How is flea allergy dermatitis treated?

Treating flea allergy dermatitis involves treating the scratches, lesions and skin allergy, as well as targeting the cause – which means getting rid of the fleas. A topical skin spray or hydrocortisone cream can help to alleviate the itching (but keep it away from the cat’s face). To get rid of the fleas, use a parasitic tablet or a spot-on solution for external parasites. If the cat has secondary infection from scratching an open wound, an antibiotic will be necessary to get rid of the infection.

Dental disease in cats

Feline dental disease refers to a cluster of dental issues that cats may suffer from, which range from periodontal disease, gingivitis, and tooth infection, to tooth resorption. When dental plaque accumulates on the teeth and hardens into tartar, it becomes near impossible to remove without intervention (i.e. dental scaling under anaesthesia). The tartar can cause inflammation in the gums (gingivitis) and progress to periodontitis or periodontal disease in which oral infection gets into the tooth and jaw structures. Tooth resorption is the destruction of the structure of the tooth, creating painful lesions – the only solution of which is to remove the tooth.

Symptoms of dental disease

Whether mild or severe, the symptoms of dental issues in cats can include:

  • bad breath
  • excessive drooling
  • dark yellow tartar on the teeth – especially visible on the molars
  • pawing at the face/mouth
  • refusal of kibble/only eating wet food
  • lack of appetite
  • inflammation in the gums
  • bleeding gums
  • blood in the saliva
  • tooth loss

How is dental disease diagnosed?

If you’ve noticed a change in your cat’s eating habits or she’s losing weight, the vet will look in her mouth as part of the physical examination. If there is a build-up of tartar, the vet may suggest dental scaling as well as a proper dental examination under anaesthetic. During this procedure, the vet will be able to go below the gum line to remove any diseased tissue and tartar, to extract damaged teeth, and to thoroughly clean the cat’s teeth.

How is dental disease treated?

After the vet has thoroughly cleaned the cat’s teeth, they will prescribe medications to facilitate healing and disease prevention. Antibiotics, anti-inflammatories and other medications will help to improve the cat’s dental health. In order to prevent dental decay, cat owners should brush their feline’s teeth daily. Only use vet-approved toothbrushes and toothpastes to brush your cat’s teeth. This is best started during kittenhood to get your kitten used to having their teeth brushed. However, if your cat does not tolerate a toothbrush, then a dental diet, cat chews, oral rinses and water additives can help to maintain your cat’s oral health.

Hypertrophic cardiomyopathy (HCM) in cats

Hypertrophic cardiomyopathy (HCM) is the most common type of feline heart disease. It is estimated that approximately 15% of cats (one in seven) will develop HCM. It involves the thickening of the heart muscle of the left ventricle (where blood is pumped from the heart back into the body). Thickened muscle reduces the efficiency of the heart to supply the body with oxygenated blood. Since the body requires oxygen, the heart has to work harder and pump faster to maintain an adequate oxygen supply.

Not all cats with hypertrophic cardiomyopathy show symptoms of the disease, but those that do will generally develop congestive heart failure as the heart is progressively less able to function normally.

Symptoms of hypertrophic cardiomyopathy in cats

Since the thickening heart muscle restricts the heart’s ability to function, this inefficient functioning will show up in areas where a lack of oxygen is obvious:

  • lethargy
  • panting/open-mouthed breathing/wheezing
  • difficulty breathing
  • increased heart rate
  • arrhythmia (irregular heartbeat)
  • blood clots/thromboembolism
  • vomiting
  • lack of appetite
  • fluid in lungs/abdomen (causes swelling in abdomen)
  • discoloured gums and foot pads
  • weakness
  • fainting

It’s important to note that many cats with HCM have no overt symptoms of heart disease at all. This is why an annual health check-up is crucial; the vet may be able to detect arrhythmia, even if the cat appears to be fine.

How is hypertrophic cardiomyopathy diagnosed?

After a physical examination, the veterinarian will conduct a full blood panel, take X-rays and listen to the cat’s heart and lungs. An echocardiogram (ECG) or heart ultrasound will give the vet an in-depth view of the heart and allow them to see how the blood flows between the chambers and into and out of the heart.   

How is hypertrophic cardiomyopathy treated?

Unfortunately, the heart is a non-regenerative organ, meaning that damage to the heart muscle results in permanent changes. Because HCM is a progressive disorder with no cure, the vet can only prescribe medications and administer a treatment plan to try to reduce the effects of the symptoms – ultimately aiming to slow the progression of the disease. Medications will be prescribed that can:

  • reduce fluid build-up around the lungs (diuretics)
  • reduce the heart rate and improve heart rhythm
  • reduce blood pressure
  • reduce blood clots (anti-thrombotic medication)
  • reduce anxiety and minimise breathing difficulties

Some cats’ HCM will progress slowly over years, with the vet monitoring the cat’s symptoms and managing her treatment plan over time. Some cats will quickly deteriorate with congestive heart failure progressing to full failure over a period of a year to 18 months. Each cat’s condition will be different, with their symptoms and treatments being determined by a whole range of factors – from genetics to lifestyle and dietary influences.

Arthritis in cats

As mentioned, cats have a tendency to hide their pain and physical ailments as a means of self-preservation. There are few conditions quite as case in point for this as arthritis or degenerative joint disease, which is characterised by the breakdown of cartilaginous cushioning of the joints and ligaments, resulting in painful friction between bones. Osteoarthritis can have genetic origins (breeds like Scottish folds, Munchkins, Maine Coons, Abyssinians and British longhair cats, among others), but can also be the result of wear-and-tear, traumatic injury, ageing, and be aggravated by obesity.

Symptoms of arthritis

Since osteoarthritis affects the joints, cats can start limping, suddenly refuse to jump up or down from furniture and other high surfaces, and may avoid using the stairs. They may get up or lie down with difficulty, or walk stiffly. The condition can also reduce their body’s flexibility and suppleness, which can result in a change in toilet habits and their ability to groom themselves. If your cat looks normal, but their fur is matting and tangling more than usual or they’re taking on a scruffy appearance, they may be experiencing pain in their spine and legs.

How is feline arthritis diagnosed?

Up to 90% of cats aged 12 years old and older have some form of osteoarthritis. Veterinarians will start to look for the signs of arthritis at your cat’s annual check-up from the age of seven years old, in order to reduce their joint discomfort. If, however, you notice any behavioural changes in your cat that may indicate pain in her joints, ask the veterinarian to check. An X-ray can reveal joint changes and inflammation/thickened joints.

How is feline arthritis treated?

Proper weight management is the most important and effective treatment to help relieve compression on the joints, so make sure that your cat is not overweight. Speak to the vet about a prescription diet. Since arthritis is a degenerative disease, it cannot be reversed, but there are several treatments to help slow its progression and manage the pain associated with arthritis:

  • non-steroidal anti-inflammatories (NSAIDs) for pain and inflammation
  • nutraceuticals/supplements for joint health, such as glucosamine and chondroitin, and omega-3 fatty acids
  • physiotherapy to manage pain
  • surgery – only for specific cases

A memory foam cat bed can also help to support her joints, while raised food and water bowls ensure that your cat doesn’t have to strain her back and joints while eating. Facilitate your cat’s climb onto furniture and higher surfaces with a pet ramp or pet stairs, and make sure your flooring is non-slip, as this can really hurt your cat’s joints. 

Gastrointestinal problems in cats

Gastrointestinal (GI) problems are some of the most common reasons why cat owners take their pets to the vet. Some cats may vomit occasionally as a normal part of their physiology, but when vomiting, diarrhoea, constipation, pain, dehydration, distension and other GI symptoms persist or worsen after more than 24 hours, it’s time to visit the vet.

Causes of gastrointestinal problems

Serious GI problems are the symptoms of many different physical issues in the body, and can be caused by the following:

  • parasites like worms (especially tapeworms from fleas)
  • dietary indiscretion (eating something they shouldn’t have, like a lizard or a bird)
  • hairballs
  • sudden diet change
  • GI obstruction from swallowed objects
  • inflammatory bowel disease (IBD)
  • stress
  • food allergies
  • pancreatitis
  • cancer

How are GI problems diagnosed?

The vet will ask about your cat’s litterbox habits, perform a physical examination, and may even request a faecal sample, do urinalysis, take X-rays, do a blood workup and any other testing to rule out or confirm the cat’s condition.

How are GI problems treated?

The cause of the cat’s GI problems will be treated to restore the cat’s health, but the vet will also provide supportive treatment for the symptoms where necessary.


It can be difficult to tell when your cat is ill, but any deviation from her usual behaviour can be a subtle indicator that she’s in pain or that something is out of balance. Cats do not like to show any kind of weakness, so it’s up to you to notice when something is amiss. In light of this, it’s a good idea to approach your cat’s health with a preventative strategy: make sure their vaccinations are up to date, maintain a regular regimen of parasitic preventative care, and schedule a yearly appointment with the vet for a general health check.

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