Understanding Cat Diarrhoea
Diarrhoea in cats is one of the most common reasons owners find themselves calling the vet — or frantically searching for answers at midnight. The good news is that most cases are short-lived and resolve on their own. The less welcome news is that some cases signal something more serious that genuinely does need veterinary attention. Knowing the difference could save your cat a lot of discomfort, and potentially save their life.
Diarrhoea is defined as loose, watery, or more frequent stools than normal. It can originate from the small intestine, the large intestine, or both — and the location actually matters quite a bit when it comes to figuring out the cause.
Small Intestine vs Large Intestine Diarrhoea
Small intestinal diarrhoea tends to produce large volumes of watery stool, sometimes with a dark or tarry appearance if there is bleeding higher up in the gut. Cats may lose weight and appear generally unwell. Large intestinal diarrhoea, by contrast, involves smaller, more frequent stools — often with visible mucus, a sense of urgency, and straining. Blood may appear bright red.
This distinction helps your vet narrow down the cause considerably, so it is worth observing your cat's litter tray carefully before your appointment.
Common Causes of Cat Diarrhoea
- Sudden changes in diet or introducing a new food too quickly
- Dietary indiscretion — eating something they should not have
- Intestinal parasites such as roundworms, Giardia, or Tritrichomonas foetus
- Bacterial infections including Salmonella or Campylobacter
- Viral infections such as feline panleukopenia
- Food intolerances or allergies, particularly to proteins like chicken or fish
- Stress and anxiety, which are surprisingly powerful triggers in cats
- Inflammatory bowel disease or other chronic conditions
- Hyperthyroidism in older cats
- Antibiotic or other medication side effects
When to Manage at Home
If your cat is bright, alert, eating, drinking, and showing no other symptoms, a single episode of loose stool is usually nothing to panic about. Mild diarrhoea lasting less than 24 to 48 hours in an otherwise healthy adult cat is often safe to monitor at home.
The most effective home approach is a temporary switch to a bland, easily digestible diet. Boiled chicken or white fish with plain boiled rice in a roughly 1:3 ratio works well for most cats. Feed small amounts every few hours rather than one large meal. This gives the gut lining time to settle and recover without being overwhelmed.
Probiotics formulated specifically for cats can also help restore the balance of beneficial gut bacteria disrupted during a digestive upset. Look for products containing strains such as Enterococcus faecium or Lactobacillus acidophilus. Human probiotics are not equivalent and are best avoided.
Hydration is critical. Cats with diarrhoea lose fluids rapidly, and dehydration can set in faster than most owners realise. Encourage water intake with a pet fountain or by adding warm, low-sodium broth to water. If your cat refuses to drink, this becomes an urgent reason to visit the vet.
When to See a Vet Immediately
There are clear signals that home management is not appropriate and that your cat needs professional assessment without delay.
- Diarrhoea lasting more than 48 hours without improvement
- Blood in the stool, whether dark and tarry or bright red
- Vomiting alongside diarrhoea — this combination dehydrates cats very quickly
- Lethargy, hiding, or a significant change in behaviour
- Complete refusal to eat or drink
- Signs of abdominal pain such as hunching, reluctance to be touched, or vocalising
- Suspected ingestion of a toxic substance or foreign body
- Young kittens or elderly cats — both are far more vulnerable to rapid deterioration
Kittens under six months are particularly at risk. What presents as mild diarrhoea in an adult cat can become life-threatening in a kitten within hours. Never take a wait-and-see approach with a very young cat.
What Your Vet May Investigate
Your vet will likely take a thorough history, including recent diet changes, travel, access to other animals, and medication history. A faecal sample is often the first diagnostic step and can identify parasites, bacteria, and abnormal cell types. Blood tests may follow to check for systemic disease, particularly if the diarrhoea is recurrent or accompanied by weight loss.
Imaging such as ultrasound can reveal thickening of the intestinal wall, abnormal lymph nodes, or masses — findings that point toward conditions like inflammatory bowel disease or intestinal lymphoma, both of which require more targeted investigation.
Preventing Future Episodes
Diet plays a central role in gut health. If your cat's diarrhoea is recurring, keeping a food diary can help you identify patterns. Transition to any new food gradually over seven to ten days rather than switching abruptly. This simple step prevents a surprising number of digestive upsets.
Regular parasite treatment is equally important. Even indoor cats can pick up parasites, particularly in multi-cat households. Speak to your vet about an appropriate deworming schedule.
Finally, do not underestimate stress as a trigger. Cats are creatures of habit, and changes to their environment — a new pet, a house move, building work, or even rearranged furniture — can translate directly into digestive symptoms. Pheromone diffusers, consistent routines, and safe hiding spots all contribute to a calmer, healthier gut.