My Cat Has Diarrhea — Symptom Assessment & What To Do

Diarrhea in cats ranges from mild and short-lived to a sign of serious illness. This guide helps you assess severity, common causes, home checks, safe care, and when to see a vet.

Quick Assessment

• Is this an emergency?

• Most common immediate cause: sudden diet change or dietary indiscretion (new food, table scraps, garbage).
• When to see a vet: diarrhea that lasts >48 hours, any blood/mucus in stool, repeated episodes (>3–4 times/day), concurrent vomiting, weight loss, poor appetite, or any sign of systemic illness.

What this symptom looks like

Diarrhea ranges from loose, unformed stool to watery or liquid stool. Owners may notice:

• Soft or mushy clumps vs. fully formed stools
• Watery puddles in the litter box
• Mucus on the stool surface
• Fresh blood (bright red) or digested blood (black/tarry)
• Increased frequency (several small stools per day)

Possible causes (ranked by likelihood)

(Reference: Merck Veterinary Manual — Diarrhea in Small Animals)

Decision tree: quick triage

• If diarrhea + collapse, weakness, pale gums, rapid breathing → likely severe dehydration/bleeding/toxin → Emergency vet now.
• If watery diarrhea + repeated vomiting or inability to keep water down → likely systemic illness, toxin, or pancreatitis → Seek same-day veterinary care.
• If soft stool only, bright appetite, normal energy, no vomiting, started after diet change → likely dietary upset → home monitoring 24–48 hours + bland diet.
• If chronic soft stool (weeks to months) + weight loss → likely IBD, food sensitivity, parasites, or hyperthyroidism → schedule veterinary evaluation including fecal testing, bloodwork, and diet trial.
• If stool contains fresh blood or black/tarry material → possible lower or upper GI bleeding → immediate veterinary evaluation.

Home assessment steps (what to check and measure)

When It's an Emergency — red flags

Seek immediate veterinary care if your cat has any of the following:

• Collapse, severe weakness, or unresponsiveness
• Continuous vomiting and diarrhea with inability to keep water down
• Repeated diarrhea with pale or very tacky gums, rapid breathing, or fainting
• Bloody stool (large amounts of bright red blood) or black, tarry stool
• Temperature >103°F (39.5°C) or <99°F (37.2°C) (low temp may indicate shock)
• Severe abdominal pain (vocalizing, hunched posture), sudden distended abdomen
• Known toxin ingestion or access to rat poison, antifreeze, human medications

When to Schedule a Vet Visit (non-urgent but needed)

Make an appointment within 24–48 hours if you see any of:

• Diarrhea lasting >48 hours
• Repeated episodes (more than 3–4 stools/day)
• Any blood or persistent mucus in the stool
• Decreased appetite or weight loss
• Ongoing lethargy or low energy
• Kittens, elderly cats, or cats with other chronic illnesses
• Household cats affected as well — contagious causes possible

(Reference: Merck Veterinary Manual)

Home Care — safe things to do while you monitor

• Withhold food for 6–12 hours in adult cats with watery diarrhea but still drinking; short fast can settle the gut. (Do not fast kittens — they need calories and veterinary attention sooner.)
• After fasting, offer a bland diet in small, frequent meals: a prescription gastrointestinal diet, boiled chicken (no skin, no bones, no seasoning) with plain white rice for a short period, or a veterinary-recommended hypoallergenic/novel-protein diet. Resume regular diet gradually over 3–7 days once stools firm.
• Ensure fresh water available at all times; encourage intake. Offer water bowls in multiple places.
• Probiotics: products formulated for cats (veterinary probiotics/synbiotics) can support recovery. Examples commonly used include Purina FortiFlora and veterinary-prescribed preparations. Follow label dosing and ask your vet before starting if your cat is immunocompromised. (See notes below.)
• Deworming: many veterinarians will recommend routine deworming or fecal testing; do not give over-the-counter dewormers without vet guidance.
• Avoid human anti-diarrheal medications (e.g., loperamide) unless specifically prescribed by your veterinarian — these can be dangerous in cats.
• Keep your cat confined to monitor litter box use and prevent exposure to other animals.

Probiotics — what owners should know

• Probiotics can help restore normal gut flora after dietary upset, antibiotics, or some GI illnesses. Use products labeled for cats or prescribed by your veterinarian.
• Look for veterinary-backed brands or products that list specific strains and colony-forming units (CFU) per dose. Avoid unverified supplements.
• WSAVA and veterinary guidance recommend choosing species-appropriate formulations and using them as an adjunct to, not a replacement for, veterinary care when needed.
• If your cat is severely ill, immunocompromised, or if diarrhea is acute and severe, check with your vet before starting probiotics.

Managing chronic soft stool (long-term strategies)

If your cat has ongoing loose stools, long-term management commonly includes:

• Thorough diagnostics: repeated fecals/PCR, bloodwork (CBC/Chem), T4, abdominal ultrasound, and possibly endoscopic or surgical biopsies to rule out IBD or intestinal lymphoma.
• Diet trial: an 8–12 week strict trial on a novel-protein or hydrolyzed prescription diet (do not mix with treats or other foods). Many cases of chronic soft stool respond to diet change.
• Deworming protocol: empirical deworming or targeted treatment if parasites are found.
• Anti-inflammatory or immunosuppressive medications for confirmed IBD (only under veterinary prescription and monitoring).
• Probiotics and dietary fiber: soluble fiber supplements (psyllium, canned pumpkin in small amounts) can help bulk stool in some cats — discuss amounts with your vet.
• Address underlying disease: treat hyperthyroidism, pancreatitis, or chronic kidney disease if they are contributing.
• Stress reduction: consistent routine, environmental enrichment, multiple litter boxes, pheromone diffusers (Feliway) can reduce stress-related colitis.

What to tell your vet (prepare this before the visit)

• Onset: when did the diarrhea start? Was it sudden or gradual?
• Pattern: number of episodes per 24 hours, consistency, color, presence of blood or mucus.
• Appetite and drinking: changes in food and water intake.
• Vomiting: frequency and timing relative to diarrhea.
• Weight changes: recent loss or gain.
• Environment: indoor/outdoor, recent boarding, other pets affected, possible toxin exposure.
• Diet history: current food, recent changes, treats, table scraps, supplements
• Medications and vaccines: any drugs (including flea/tick, recent antibiotics) and vaccine status
• Stool sample: bring a fresh sample in a sealed container
• Prior history: previous episodes, chronic illnesses (kidney disease, diabetes, hyperthyroidism)

Closing notes and sources

Diarrhea is a common symptom with a wide range of causes. Many mild cases resolve with simple home care and monitoring, but persistent, bloody, or severe diarrhea requires timely veterinary assessment. If you are ever unsure, contact your veterinarian — it’s better to be cautious when a cat’s hydration, appetite, or behavior changes.

Primary source: Merck Veterinary Manual — Diarrhea in Small Animals (https://www.merckvetmanual.com)

Additional guidance: WSAVA Probiotic Guidelines and veterinary clinical protocols for feline GI disease.

Frequently Asked Questions