Dog vomiting yellow: what it means and when it is serious

Reading time 6 min · Level 1: Why the symptom happens

The short answer: The yellow in the vomit is bile. In a dog that is otherwise bright, the most common explanation is that the stomach has been empty for too long, often early in the morning or late in the evening. Bile from the intestine then flows back up into the stomach and irritates the lining. A small late-evening snack, or more and smaller meals, usually changes this. But bile also comes up with gastritis, when the dog has eaten something unsuitable or when something is stuck. If your dog vomits several times in a short period, brings up blood, cannot keep water down or seems lethargic, it should see a vet the same day.

What the yellow actually is

Bile is made in the liver and released into the small intestine, just after the stomach, where it helps break down fat. Normally it only moves in one direction. When contents from the small intestine flow backwards into the stomach, the lining becomes irritated and the dog brings up a yellow or yellow-green, often frothy fluid⁴. Evidensia describes the same thing from the gastritis side: the yellow or green colour in vomit comes from bile².

So the colour tells you where the contents came from. It does not tell you how serious it is. For that you need to look at the dog as a whole, at when it happens and how often.

Five common explanations

1. The stomach has been empty for too long. Yellow or white froth usually points to an empty, irritated stomach or excess stomach acid. It is most common in the morning or when there is a long gap between meals¹. The pattern has its own name, bilious vomiting syndrome. In a published case series of 20 dogs at a veterinary teaching hospital in the United States, the typical patient was a young dog with a long history of vomiting bile early in the morning. More frequent meals and a late evening meal were part of the treatment, and twelve of the seventeen dogs that kept the diagnosis improved⁴.

2. Gastritis. With inflammation of the stomach lining, vomiting is the most common sign. Sometimes it comes straight after eating, sometimes mainly when the stomach is empty, for example at night. The dog may also eat grass, have a poorer appetite or bad breath².

3. The dog has eaten something unsuitable. A dog that vomits has most often eaten something it should not have³. Leftovers, rubbish, something from the woods. Once the stomach has emptied, often only fluid and bile come up.

4. Something is stuck. Dogs swallow toys, socks and string. An object lodged in the stomach or intestine causes repeated vomiting and can damage the lining³. This is an emergency.

5. Disease elsewhere in the body. Vomiting can be a sign of disease in other organs, including the kidneys and liver, or of hormonal disease¹. Then the vomiting is rarely the only sign.

Worth knowing: in the case series above, the diagnosis was changed in three of the 20 dogs, one of them to stomach cancer. The authors also noted that the dogs had rarely been investigated thoroughly enough for bilious vomiting to be the only explanation left⁴. It is a conclusion the vet reaches once other causes are ruled out, not a label to put on a dog that keeps vomiting.

When to see a vet

The same day, or straight away if your dog:

• vomits blood or something that looks like coffee grounds¹
• cannot keep water down, or vomits several times in a short period³
• is lethargic, has a fever or a low temperature. Normal temperature is 38 to 39 degrees Celsius³
• may have swallowed something poisonous or an object¹
• has a swollen, tight belly and tries to vomit without anything coming up⁵
• is a puppy or a small dog, since they quickly become dehydrated¹

Within a few days if the vomiting has not settled within a day despite a bland diet, if it keeps coming back³, if the morning vomiting continues even though you have changed the meals, or if your dog is losing weight.

If you are unsure whether your dog is dehydrated, feel the gums. They should be shiny and moist, not sticky. Also lift a little skin on the back. Normally it drops straight back, but with dehydration a fold stays standing³.

What you can do yourself

For the typical morning vomit. Give a small snack before bedtime, or split the day's food into more and smaller meals¹. If the morning vomiting disappears within a couple of weeks you have probably found the explanation. If it does not, it is time for the vet.

After a single vomit in a bright dog. Offer water in small amounts. If it stays down you can move on to a bland diet³. Evidensia suggests one third boiled white fish or chicken and two thirds well-cooked white rice. On the first day a teaspoon to a tablespoon per meal is enough depending on size, spread over six to eight small meals. Increase the amount over two to three days and then return to the usual food over four to seven days¹.

Do not let a puppy fast. A puppy should not go without food for more than a few hours³.

Never give medicines on your own initiative. The wrong medicine can make things worse¹.

Take notes. Time of day, how often, what came up and what the dog ate the day before. A photo helps too. It makes the vet's assessment much easier.

Frequently asked questions

Why does my dog vomit yellow in the morning?

Usually because the stomach has been empty all night. Bile and stomach acid irritate the lining so that the dog brings up yellow froth before breakfast. A small evening snack is usually the first step.

Is it dangerous when a dog vomits yellow froth?

Once, in a lively dog, it is rarely dangerous. Repeated vomiting, blood, lethargy or being unable to keep water down are reasons to contact a vet.

What is the difference between yellow and white froth?

Both are seen with an empty, irritated stomach. The yellow colour means bile has come up too. How often it happens and how the dog feels tell you more than the colour.

Should my dog fast after vomiting?

Start with water in small amounts and then small portions of a bland diet if the water stays down. Puppies should not go without food for more than a few hours.

That was the short answer. If you have a question about your own pet, email us at info@herbiovet.se. We reply within one working day.