Dog Throwing Up Yellow: Causes, Bile Vomiting and When to See a Vet

What the yellow color means

The color of the vomit gives clues:

Yellow: usually bile. It also confirms your dog is really vomiting and not regurgitating.
Green: often caused by eating grass, which can sometimes be a sign of stomach upset.
Red (blood): a warning sign, and a vet should see your dog.
Like coffee grounds: digested blood.

Vomiting is an active process: your dog retches and brings up stomach contents. Regurgitating is passive, with no warning. If you can, film it: it helps your vet.

When to see the vet

Go to the emergency vet right now if your dog:

Vomits repeatedly over hours, or can't keep water down.
Has blood or coffee-ground vomit, or black, tarry stools.
Is very lethargic, weak or has collapsed.
Has a bloated or painful belly, or retches with nothing coming up.
May have swallowed an object, a toxin or a medication.
Has trouble breathing, a fever or yellowish skin or eyes.

Make an appointment today if your dog is bright, but:

Vomits yellow more than once or on several mornings in a row.
Has diarrhea, eats less or has lost weight.
Vomits at other times of the day, not just in the morning.

If the vomiting lasts more than 4 to 6 hours, or is frequent or severe, call your vet right away.

The most common causes

Bilious vomiting syndrome. The classic: vomiting of yellow fluid, mostly first thing in the morning, in a dog who otherwise seems healthy. It happens after a long fast: bile irritates the empty stomach. It affects young and adult mid-sized dogs, with no particular breed. It's diagnosed by ruling out other causes.
Gastroenteritis. Vomiting and diarrhea, sometimes with foamy, yellowish bile. They can come from infections, medications or a new food.
Blockage or foreign object. There may be only a few episodes of vomiting and it can still be a life-threatening blockage.
Acute pancreatitis.
Intestinal parasites, infections or allergies.
Inflammatory bowel disease or cancer.
Diseases outside the gut, like diabetes, kidney or liver disease, or Addison's disease.
Eating too fast or eating grass, although grass causes vomiting in fewer than a quarter of the dogs who eat it.

How bad the vomiting is doesn't always reflect how serious the disease is: a dog with a blockage may vomit only a few times, while another that ate something that disagreed with them can vomit many times and recover quickly. That's why the whole picture matters.

What to do in the meantime

Write down when it started, at what time and how many times your dog vomits, whether it's getting worse and what's in the vomit.
Watch whether your dog is bright, eating and drinking, has diarrhea, coughing or pain, and whether there's been a diet change or access to trash, medications or plants.
Take a photo or video of the vomit and of how your dog vomits.
Don't give human medications or stomach protectors unless your vet says so.
If it was a single episode and your dog is bright, watching is enough.

What the vet will do

They'll ask for details (food, trash, medications) and examine your dog. Depending on the case, they may run bloodwork and a urinalysis, X-rays or an abdominal ultrasound. If your dog is dehydrated, they'll give IV fluids.

For bilious vomiting syndrome, the first thing recommended, once other causes are ruled out, is a small late-night meal, part of dinner, to shorten the overnight fast. If that doesn't work, your vet may prescribe a digestive diet or a medication that helps the stomach empty.

In the US, an emergency exam averages about $135, a blood count about $104, a chemistry panel about $164, X-rays about $172 and an ultrasound about $483. A hospital stay averages about $1,323 at an emergency clinic (Synchrony/CareCredit 2025-2026 cost study). Costs vary by region and clinic. More in what a vet visit costs.

Frequently asked questions

Why does my dog throw up yellow in the morning?

The most common reason is bilious vomiting syndrome: after a night without food, bile irritates the empty stomach. If it happens now and then and your dog is fine, it may be that. If it keeps happening for weeks or months, get it checked: don't write it off as a "sensitive stomach."

Is it the same as throwing up white foam?

It's similar: yellow, green or white foamy vomit is usually bile, and it's linked to an empty stomach and to different digestive problems. See also what to do if your dog is throwing up white foam.

When is it serious?

When the vomiting is repeated over hours, there's blood, your dog is lethargic, the belly is painful or bloated, or your dog may have swallowed something they shouldn't have. Also if it comes with diarrhea, poor appetite or weight loss.

How can I tell if my dog is vomiting or regurgitating?

Vomiting is active: there's retching and the stomach contracts. Regurgitating is passive and happens with no warning. If you're not sure, film it and show your vet.

What if the vomit is green?

It's often from eating grass. Still, it can signal stomach upset: if it keeps happening or there are other symptoms, see your vet.

Sources

This article is for general information and does not replace diagnosis or treatment by a veterinarian. If you are worried about your pet's health, call your vet clinic.