By Dr Duncan Houston
A streak of red on the litter or stool can be alarming. The amount matters, but your cat's energy, appetite, pain and urine output matter just as much.
Blood is a reason to seek advice, not a diagnosis. The aim is to identify its source and avoid missing a cat that is becoming seriously unwell.
Quick Answer
Bright red blood often comes from the lower digestive tract, while black, sticky, tar-like stool may contain digested blood. Contact your vet about any blood in the stool, particularly if it recurs. Large amounts, black tarry stool, weakness, pale gums, repeated vomiting or severe pain require urgent care.
What does the appearance tell you?
A small fresh streak on a firm stool can occur with irritation near the rectum, while blood and mucus mixed with frequent small loose stools can suggest large-bowel inflammation. Black tar-like stool is different from ordinary dark brown faeces and may reflect bleeding higher in the digestive tract or swallowed blood.
Food and some medicines can also change colour. A photo and medication list help the vet interpret it. PDSA's guidance on blood in cat poo explains why associated illness changes the urgency.
How quickly should you act?
| Finding | Action |
|---|---|
| One tiny fresh streak, otherwise bright and eating | Call for advice, save a photo and monitor closely for recurrence. |
| Repeated blood, diarrhoea, constipation or appetite reduction | Arrange prompt assessment, generally the same day if ongoing. |
| Black tarry stool, substantial bleeding, pale gums or marked weakness | Seek urgent emergency care. |
| Straining repeatedly without producing urine | Treat as a urinary emergency, especially in a male cat. |
What can cause it?
Diet-related irritation, parasites, infectious disease, constipation, chronic intestinal inflammation, polyps and tumours are possibilities. Ulceration, clotting disorders or medication toxicity may cause more serious bleeding. Stress can contribute to digestive changes, but should not become the assumed explanation before other causes are considered.
Kittens, older cats and cats with chronic disease may have less reserve. Mention possible access to rodent poison, human medicines, string or bones immediately.
How do vets find the cause?
The vet assesses hydration, circulation, abdominal comfort and the area around the anus. A fresh faecal sample may be tested for parasites or other organisms. Blood tests can assess anaemia, organ function and clotting when indicated. Imaging or intestinal sampling may be needed for persistent disease or suspected obstruction.
The Merck guide to feline stomach and intestinal disorders discusses the range of causes and why treatment must match the findings.
When is it an emergency?
Go immediately for collapse, severe abdominal pain, substantial bleeding, black tarry stool with illness, or very pale gums. Repeated litter straining may be mistaken for constipation when the bladder is blocked. If you cannot confirm urine is passing and the cat is distressed, do not wait.
What should you do now?
- Photograph the stool and note frequency, amount and whether it is firm or watery.
- Collect a fresh sample in a clean sealed container if practical.
- Check actual urine production, particularly in shared litter trays.
- Offer access to water and ask the vet what to feed. Do not impose a prolonged fast.
- Bring details of food changes, medicines, parasite control and possible toxin exposure.
Common mistakes
Do not give human anti-diarrhoea medicines, painkillers or enemas. Some human enemas are highly dangerous to cats. Avoid repeated diet swaps, assuming deworming covers every parasite, or treating all bloody diarrhoea with antibiotics. Never pull visible string from the mouth or anus.
Prevention and follow-up
Make diet changes gradually, maintain a suitable parasite-control plan, keep toxins and swallowable objects inaccessible and clean trays regularly. Provide enough separate resources to reduce conflict. If bleeding recurs after treatment, return for reassessment rather than repeatedly using leftover medication.
Frequently Asked Questions
Is one small streak always an emergency?
Not always in an otherwise well cat, but it warrants veterinary advice and monitoring.
Does blood mean cancer?
No. Many causes are possible, and examination guides the investigation.
Can constipation cause fresh blood?
It can, but confirm that the cat is passing urine and seek help for repeated straining.
What is melena?
Black, tarry faeces containing digested blood. It needs urgent assessment.
Use the whole picture to judge urgency. A photo and clear observations help, but weakness, pain or abnormal urine output should send you straight for care.
For more practical animal health information, explore ASK A VET™. Your own veterinary team can help tailor the next steps to your cat or dog.
The ASK A VET™ Tracker logs live location and activity trends, so a change in routine never goes unnoticed.
- Blood in Stool
- Cats
- Diarrhoea
- Digestive Health
Every ASK A VET article is written and reviewed by qualified veterinarians.
