Symptom guide

Blood in Dog Poop: What Red or Black Stool Means

Bright red streaks, jelly-like bloody diarrhea or black tarry stools: what blood in your dog's poop can mean and when it's an emergency.

Updated October 2026 · 7 min read · By the Hushku editorial team · 3 sources

See a vet within 24 hours. Same day for large amounts, black stool or a sick dog

Short answer

A small streak of bright red blood or mucus on an otherwise normal stool, in a dog that's bright and eating, is often from colon irritation and may settle within a day or two, but call your vet if it continues. Large amounts of blood, 'raspberry jam' diarrhea, black tarry stools, or blood with vomiting or lethargy need a vet the same day. Puppies with bloody diarrhea need a vet immediately because of the risk of parvovirus.

Key facts

Bright red blood comes from the lower gut; black, tarry stool from higher up.
Black stools need a vet promptly.
Bloody diarrhea in a puppy can be parvovirus: an emergency.
Sudden 'raspberry jam' diarrhea can cause rapid dehydration in small dogs.

This guide is general information, not a diagnosis. If your pet seems unwell, or you're worried, call your vet.

Overview

The colour of the blood tells you roughly where it's coming from.

Bright red blood (haematochezia) comes from the lower intestine: the colon or rectum. It often appears as streaks or spots, sometimes with mucus and straining, and is commonly caused by colitis (inflammation of the colon) after scavenging, a diet change or stress.

Black, tarry stools (melena) contain digested blood from higher up: the stomach or small intestine. This can be caused by ulcers (including from anti-inflammatory medicines), bleeding disorders, swallowed blood or tumours, and needs prompt veterinary attention. Note that iron supplements and some foods can also darken stools.

A sudden onset of large amounts of watery, bloody diarrhea that looks like raspberry jam can be acute haemorrhagic diarrhea syndrome (formerly called HGE), which can cause rapid dehydration, especially in small breeds.

Go to a vet now if you see

Black, tarry stools, or vomit that contains blood or looks like coffee grounds
Large amounts of blood or raspberry-jam diarrhea
Bloody diarrhea in a puppy or an unvaccinated dog
Lethargy, weakness, pale gums or collapse
Possible access to rat poison or human medicines

Common causes

1. Colitis from diet or scavenging
Usually mild
Soft stools with mucus and fresh blood, frequent small poops and straining. Often settles quickly.
2. Stress colitis
Usually mild
Bloody, mucousy diarrhea after kennels, travel, house moves or other stress.
3. Intestinal parasites
Needs a vet
Whipworms and hookworms can cause bloody stools; giardia causes soft, smelly diarrhea.
4. Parvovirus
Serious
Severe, bloody, foul-smelling diarrhea with vomiting and lethargy in unvaccinated puppies and young dogs. An emergency.
5. Acute haemorrhagic diarrhea syndrome
Serious
Sudden, profuse raspberry-jam diarrhea, often with vomiting, most common in small and toy breeds.
6. Anti-inflammatory medicines and stomach ulcers
Serious
NSAIDs, steroids or human painkillers can cause ulcers and black stools.
7. Rat poison (anticoagulant)
Serious
Causes bleeding from anywhere, including the gut, often days after eating it.
8. Anal gland problems, tumours or polyps
Needs a vet
Blood on the outside of the stool or after passing it, more common in older dogs.

What you can do at home

Take a photo of the stool, and bring a fresh sample to the vet if you can.
For a single mild streak in a bright adult dog, offer small, bland meals and plenty of water, and watch closely.
Don't give human anti-diarrhea or painkilling medicines.
Keep your dog away from other dogs until you know the cause.

When to see a vet

Blood in the stool for more than a day, or more than once
Diarrhea lasting more than 24 to 48 hours
Straining, pain or a swollen belly
Weight loss or poor appetite
Any blood in the stool of a dog on anti-inflammatory medication

Prevention

Vaccinate puppies against parvovirus and complete the full course
Keep to a regular deworming and stool-testing schedule
Change foods gradually over 7 to 10 days
Keep rat poison, medicines and rubbish out of reach

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Sources

We check guides against veterinary sources and update them when guidance changes. How we write and review.

Questions.

Can stress cause blood in a dog's stool?

Yes. Stress colitis is a common cause of bloody, mucousy diarrhea after kennels, travel or upheaval, and usually settles quickly with treatment.

Is a little blood after a hard poop serious?

A tiny spot after straining to pass a hard stool can be from minor irritation, but recurring blood should be checked.

What does mucus in dog poop mean?

A little mucus is normal. More mucus, often with fresh blood, usually means the colon is inflamed.

Key facts

Overview

Go to a vet now if you see

Common causes

1. Colitis from diet or scavenging

2. Stress colitis

3. Intestinal parasites

4. Parvovirus

5. Acute haemorrhagic diarrhea syndrome

6. Anti-inflammatory medicines and stomach ulcers

7. Rat poison (anticoagulant)

8. Anal gland problems, tumours or polyps