Dog Throwing Up Yellow Bile: Causes and When to Worry

Finding a puddle of bright yellow foam on the floor first thing in the morning is unsettling, but it is one of the most common things dog owners see, and in most cases it has a simple explanation. The yellow colour comes from bile, and the most frequent reason bile ends up in vomit is that your dog’s stomach has been empty for too long.

This article explains where the yellow comes from, the handful of other causes worth knowing about, what you can change at home, and when it is time to call the vet.

Why the vomit is yellow

Bile is a yellow-green digestive fluid made by the liver and stored in the gallbladder. After a meal it is released into the first part of the small intestine (the duodenum), where it helps break down fats. It is not meant to be in the stomach.

When the stomach is empty, though, some bile can flow backwards from the duodenum into it. Bile irritates the stomach lining, and the stomach responds by emptying itself, which is why what comes up is mostly liquid, foam or mucus tinged yellow, rather than food. If the vomit is more green than yellow, it is still usually bile. Very green material can also come from eating grass.

The empty-stomach pattern: bilious vomiting syndrome

Some dogs vomit yellow bile repeatedly in a very recognisable pattern, which vets sometimes call bilious vomiting syndrome. The typical picture is:

• vomiting yellow foam or liquid, but not food
• usually early in the morning, or late at night, or shortly before a meal is due
• happening every few days or weeks
• a dog that is otherwise completely well: eating normally, normal stool, no weight loss.

The exact cause is not fully understood, but it is thought to involve bile flowing back into a stomach that has been empty for many hours, along with slightly sluggish movement of the stomach and intestines. Because the dog is otherwise healthy, it is not usually dangerous. It is still worth a conversation with your vet, because other causes of vomiting need to be ruled out before the pattern is put down to an empty stomach.

Other causes of yellow vomit

Any dog that vomits more than once will eventually bring up bile, because the stomach empties of food first. So yellow vomit can appear with almost any cause of vomiting, including:

• Eating something unsuitable, such as rubbish, fatty food or grass.
• Gastroenteritis from an infection, parasites or a sudden diet change.
• Pancreatitis, often after a fatty meal, usually with belly pain and lethargy.
• A swallowed object partly blocking the stomach or intestines.
• Liver or gallbladder disease. Here the vomiting may be accompanied by jaundice (yellowing of the gums, the whites of the eyes or the skin) which needs a vet promptly.
• Other illnesses, such as kidney disease or Addison’s disease, which tend to cause vomiting that comes and goes alongside other changes like increased thirst or weight loss.

The difference between these and the empty-stomach pattern is almost always the rest of the picture. A dog with bilious vomiting is bright and hungry an hour later. A dog with pancreatitis, a blockage or liver disease usually is not.

When to call the vet

Watch at home if your dog has vomited yellow once or twice, then eats normally, drinks normally and behaves as usual. Call your vet if:

• the yellow vomiting keeps recurring, even if your dog seems well in between
• your dog vomits more than two or three times in a day
• it comes with diarrhea, loss of appetite, lethargy, weight loss or increased thirst
• your dog is a puppy, a senior or has an existing medical condition.

Go to a vet straight away for any of the emergency signs listed at the top of this page. For a fuller guide to judging vomiting of any colour, see dog throwing up: causes and when to worry.

What you can do at home

If your dog fits the empty-stomach pattern and is otherwise healthy, these changes help many dogs. Check with your vet first if your dog is on a special diet or has a medical condition.

1. Shorten the overnight gap. Move the evening meal later, or give a small, low-fat snack shortly before bed. The aim is to keep the stomach from sitting empty for too long.
2. Split meals. Feeding the same daily amount as three or four smaller meals, rather than one or two large ones, helps some dogs. Avoid long gaps of more than about 12 hours between meals.
3. Keep the diet consistent. Sudden changes of food upset many stomachs. If you do change food, mix it in gradually over a week.
4. Cut out fatty extras. Rich table scraps and fatty treats can trigger vomiting and, in some dogs, pancreatitis.
5. Keep a simple diary of when the vomiting happens and what your dog last ate. A pattern of early-morning episodes is very helpful to your vet.

After a single bout of vomiting, the usual short-term advice applies: offer small amounts of water, and start again with a small, bland meal rather than a full bowl.

What the vet may do

For a dog with the typical pattern and a normal examination, your vet may simply recommend the feeding changes above and see whether the vomiting stops. If it does not, or if anything about your dog is not quite right, they are likely to suggest blood tests to check the liver, pancreas and kidneys, and sometimes X-rays or an ultrasound scan. Some dogs are given a medicine that reduces stomach acid or one that helps the stomach empty more efficiently, usually alongside the feeding changes.

Related problems

If the vomit is white and foamy rather than yellow, read dog throwing up white foam. If your dog may have eaten something toxic, see dog poisoning: toxic foods and first steps. And for everything else to do with the stomach and bowels, browse our digestive health section.