Imagine this, waking up one morning and letting your dog in the garden to do their business, when suddenly you notice a big pile of black poo! Is this serious? What has caused this? What should I do?

As gross as it may seem, checking your dogs (and cats!) faeces on a regular basis is extremely important and I hope that after reading this article I can convince you to start. The following will explain what black poo could mean and how it can be investigated by your Vet.

Why is my dog’s poo black?

Black or tar coloured faeces indicates that there is blood present in your dog’s digestive tract, this is called ‘melena’. Black blood tells us that the problem is likely to be in the upper digestive tract (stomach or small intestine) because the body has already worked hard to try to digest this blood.

Fresh, red blood in poo would indicate a bleed in the lower digestive tract, this is called ‘haematochezia’. Dogs with melena may produce large volumes of black, tarry faeces in a short space of time, or alternatively, they may produce small volumes of black, tarry faeces intermittently over a longer period. 

Is it serious and should I be worried?

Yes. You need to contact your Vet immediately if you notice black poo. Melena may represent a life-threatening illness. As weird as it may seem, it can be very helpful for your Vet if you take a photograph of the melena to show them during your consultation (or maybe even a faecal sample from your dog!)

What could cause this?

Below is a list of the most common causes of melena in dogs. This list is by no means exhaustive, but it covers the most frequest causes;

  • Internal bleeding: Severe blood loss can be life-threatening.
  • Medication reactions: If your dog is on medication and you notice black poo, stop giving the medication and contact your Vet immediately. The most common medications which can cause gastrointestinal ulceration are corticosteroids and non-steroidal anti-inflammatories. 
  • Gastrointestinal ulceration. 
  • Parasites.
  • Toxin ingestion.
  • Liver or pancreatic disease.
  • Anaemia.
  • Haemorrhagic gastroenteritis.
  • Activated charcoal: Sometimes your Vet may prescribe activated charcoal for you to feed your dog following a harmful toxin ingestion, this will temporarily turn their faeces black. 
  • Tumours: The presence of gastric (stomach) tumours or small intestinal tumours can bleed into the gastrointestinal tract.
  • Blood clotting disorders (coagulopathies).
  • Trauma: Your dog may have an internal bleed from acute trauma, for example an RTA (road traffic accident).
  • Metabolic diseases such as Addison’s disease (hypoadrenocorticism).
  • Recent surgery on the gastrointestinal tract.
  • Stomach or small intestinal foreign bodies.
  • Ingested blood: Blood that is swallowed could cause melena. This could be from the oral cavity, throat (pharynx), lungs or through licking a bleeding wound.

Are there other signs to look out for?

Your dog may appear absolutely normal apart from the presence of melena. However, the following clinical signs can also be accompanied by black poo and must not be ignored. Some of the below clinical signs are more urgent and serious than others, I have listed the clinical signs in order of urgency.

  • Collapse.
  • Pale or white gums: When you first notice melena, a great first step would be to check the colour of your dog’s gums to make sure they are pink. Dogs with a significant bleed may be anaemic from the blood loss and pale gums often indicate anaemia.
  • Petechia: Petechia are tiny, red or purple spots on the skin or gums which indicate a bleed under the surface. 
  • Lethargy.
  • Hunched posture: This is usually associated with acute abdominal pain or discomfort.
  • Vomiting.
  • Diarrhoea.
  • Weight loss and poor body condition.

What will my Vet do?

When you take your dog to your Vet, they will first perform a full clinical examination to assess the general health of your dog. Depending on how sick and unwell your dog is, they may require hospitalisation and extensive diagnostics.

To investigate further, they will likely suggest a blood test to check organ function and to look for signs of anaemia (low red blood cells). Depending on these results, they may then suggest more complex blood tests and clotting profiles, diagnostic imaging (x-rays and ultrasound), urine tests and faecal analysis. Endoscopy may also be used to look at the inside of the upper intestinal tract. 


To conclude, examining your dog’s poo will allow you to pick up on abnormalities quicker. This can help to diagnose serious conditions before they get worse!

As unflattering as it is walking around your garden to examine your dog’s poo, I hope this article has convinced you to check your dog’s faeces regularly. This article hasn’t touched on the treatment options because the treatment and prognosis for melena is very dependent on the underlying cause. If you notice melena from your dog, it is super important to act fast and do not delay contacting your Vet.