Cat Illness – Signs of Sickness in Cats

Last Updated on June 10, 2021 by Julia Wilson

Cats are very stoic creatures by nature and it is up to the observant cat owner to keep a close eye over them and be aware of small changes in their appearance, behaviour, eating habits etc., which can indicate all is not well.

Your cat can’t tell you when something is wrong so it is important for you, therefore we must watch for clues and act accordingly. What may seem to be a minor change may be a warning of a serious medical issue.

Changes in behaviour

Inappropriate elimination

Inappropriate elimination can be the result of a behavioural issue or a medical problem. This is why it is extremely important to seek veterinary advice if your cat stops using the litter tray. He/she will run some tests to determine if there is a medical cause if so it can be treated and if it is established that it is a behavioural problem appropriate action can be taken to help your cat resolve this problem.

A cat who is urinating outside the litter tray may have a number of medical conditions such as diabetes mellitus, kidney failure, FLUTD, urinary tract infection.

Increased/decreased thirst and or appetite

There are many possible reasons why your cat may be eating or drinking more or less, some of which include:

Increased thirst is common in diabetes mellitus and chronic kidney disease. Other causes include pyometra and hyperthyroidism, which also causes an increase in appetite, despite weight loss.

Loss of appetite can be due to an abscess (bite or dental), anemia, dehydration, injury or trauma, intestinal obstruction, dental or mouth pain (gingivitis, tooth abscess, stomatitis etc.) or other disorders.

Increased vocalisation

This can be due to stress, fear, estrus or an underlying medical problem. Increased vocalisation is common in older cats due to confusion, dementia or pain.


Common causes of hiding include pain, sickness, stress, and fear.

Change in sleeping habits

Sleeping more and lethargy often a sign that something is wrong with your cat.

Change in routine or general behaviour

If your cat usually greets you when you come home from work, but abruptly stops this it could be a sign that something is wrong with kitty. Is your cat suddenly spending a lot of time in the litter tray, no longer harassing you for food first thing on a morning, or harassing you for food when it hadn’t in the past? Any change, no matter how minor could be a result of a medical condition.

General and physical signs

Coat appearance

Cats are by nature fastidiously clean and spend a great deal of their day grooming. Poor coat condition can be caused by a multitude of problems. Parasites, malnutrition, systemic disease and pain. The older cat may have problems maintaining it’s grooming regime due to pain caused by conditions such as arthritis or obesity.

Bad breath

Bad breath (halitosis) in cats is not normal and could be a sign of kidney disease, diabetes mellitus, liver disease, tooth abscess, periodontal disease, intestinal problems, cancers of the mouth.

Difficulty going to the toilet

If your cat is straining to go to the toilet, or only passing a small amount of urine, going to the toilet often or licking the genital area frequently these symptoms could be the following; FLUTD (which is a medical emergency), bladder stones, tumours, diabetes mellitus, kidney disease or constipation.

Blood in the urine (hematuria)

Bladder stones, urinary tract infection, cancer, trauma can all be causes of blood in the urine.

Weight loss or gain

There are many causes of weight loss or gain. Weight loss could be caused by diabetes mellitus, hyperthyroidism, malnutrition, kidney failure or any chronic illness.


Cats are very good at hiding pain from their carers and each cat will have a different pain threshold. There are countless causes of pain in cats, which is why it is important to seek veterinary advice as soon as possible to find out the cause. A cat in pain may be aggressive, withdrawn, hide, or sit with a hunched up appearance.


Discharge from the eyes and nose can be due to a bacterial or viral infection, or a foreign body.

Ataxia (unsteady gait)

Possible causes include poisoning, neurological disorder, ear infection, spinal trauma, pelvic fracture, brain trauma.

Abnormal breathing

Heart failure, asthma, lung disease. Panting could be a sign of hyperthermia (heat stroke).


Are the pupils both the same size? Shine a light on them, do they become smaller or stay fixed? Either scenario is a medical emergency and could indicate head trauma, seek veterinary attention immediately.

The appearance of the third eyelid (haw) is another indicator that something is wrong with your cat. This could be a sign of dehydration, illness or injury.

Appraising the situation

Gum colour – The normal colour is pink. Pale to white gums may indicate shock or anaemia. Blue gums indicate not enough oxygen, yellow gums indicate liver problems, bright red can indicate carbon monoxide poisoning or heat stroke.

Dehydration – To check for dehydration grasp some skin at the base of their neck (the scruff) and gently pull it up. In the hydrated cat, the skin will spring back immediately. In a dehydrated cat, the skin will be slower to retract. The more severe the dehydration the slower the skin will take to retract.

Capillary Refill Time (CRT) – This helps you to test your cat’s blood circulation and can indicate dehydration, heart failure or shock. To test capillary refill time lift your cat’s upper lip and press the flat of your finger against the gum tissue. Remove the pressure and you will see a white mark on the gum where your finger was placed. Using a watch with a second hand, time how long it takes for the pink colour to return to the white spot. In the healthy cat, it should take around 1 – 2 seconds to return to pink.