Dogs can vomit for many different reasons. It can sometimes be tricky to figure out what the cause is and therefore how to help them. As well as carrying out a physical examination, we can also look at the vomit in more detail; the frequency, timing and contents of the vomit can all potentially be useful. But can the colour of the vomit tell us anything?

What is vomit?

Although it sounds a fairly basic question, clinically, there can sometimes be some confusion. 

True vomit is stomach contents which is expelled forcefully and mixed with saliva as it passes up through the oesophagus and mouth. The stomach contents could include food or water which has been ingested, along with hydrochloric acid and digestive enzymes produced from cells which line the stomach. 

Regurgitation can sometimes be mistaken for vomit. It is very similar, in that it is still often either gastric or oesophageal contents. But it is a passive process rather than a forceful one and the dog may simply appear to burp rather than ‘heave’.

Why do dogs vomit?

Pick a condition and vomiting is likely to be on the list of symptoms. Common causes include:

  • gastroenteritis
  • stomach or intestinal obstructions
  • dietary indiscretion (eating something they shouldn’t!)
  • internal medical conditions such as kidney disease

In itself, vomiting is not diagnostic for any particular condition and further investigations will be needed to find out the cause. The main consequence of vomiting that we would worry about is usually dehydration or not being able to keep food or water down. Dogs will also lose electrolytes by vomiting and it can obviously make their stomach quite sore. 

Diagnosing the cause of the vomiting

For many cases, the most useful information can be gained from asking pertinent questions about the history of the symptoms and carrying out a physical examination of the dog. This is important to establish whether the dog is vomiting or regurgitating; as the causes of vomiting can be different to the causes of regurgitation. In some cases we can also potentially identify signs of a physical obstruction in the stomach or intestines. Signs of dehydration, shock, bleeding or severe pain would always require immediate treatment and further investigation. These will likely include blood work and imaging – x-ray and ultrasound. And depending on the findings, possibly endoscopy or exploratory surgery. 

Colours of vomit and what they can tell us

As vets, we are always more than happy to hear descriptions of and see photos of vomit, diarrhoea, lumps, bumps and all sorts of oddities. Vomit can appear in a rainbow of colours, and each one can help to point us in the direction of the underlying cause.


Probably the most common colour of vomit and is usually a combination of stomach acid and a small amount of bile (which is produced in the liver and secreted from the gall bladder to aid digestion of fats). Yellow vomit is not diagnostic for a particular condition or the reason for the vomiting. 


Green vomit can be a sign that the dog has been eating a lot of grass or that there is a lot of bile in the stomach. Neither is a major cause for concern unless the vomiting continues or the dog seems unwell. However dogs that have eaten rat or slug poison could produce green vomit when the blue pellets mix with the yellow stomach acid. If this is a possibility, or if it looks grainy, then seek veterinary attention right away


White vomit is often just ‘froth’ and is often seen when the dog’s stomach is empty or if they have been coughing or retching a lot. However, if the dog is persistently heaving to vomit but is only able to bring up this froth, then it could be a sign of bloat or a torsion which is a veterinary emergency and help must be sought immediately. 


Red vomit is unusual but the most common cause for the colour change is blood. This can happen if the dog has been vomiting for some time as the stomach lining becomes inflamed, but it could also be a sign of a bleeding disorder or a poison and warrants a check up. 


This is similar to red vomit in that black vomit is often also due to blood but old or digested blood which makes it appear black. This will happen if the dog has stomach or intestinal ulcers and often looks like coffee granules. These can become quite serious so always get your dog to the vet if you see this sign.


Unfortunately, often a sign that your dog has taken a liking to another animal’s faeces, or their own! However, if your dog is also unwell or the vomiting continues, is mainly liquid and smells of faeces, then it could be a sign of an intestinal obstruction and they ought to be seen by a vet as soon as possible. 

Can I tell what’s wrong with my dog by looking at the vomit?

Although it would be really helpful if the colour of a dog’s vomit was characteristic for a particular condition, sadly, this is not the case. Instead, this information needs to be used in combination with other symptoms and clinical examination findings to help determine the correct diagnostic path and hopefully, the cause. As the owner, you are the only one vets can ask questions about the history and clinical signs for your dog, so the more information you can provide, the better. And don’t forget, a picture paints a thousand words – just maybe don’t share that one on social media….

Further reading: