Vomiting in dogs: Vet shares 12 reasons why your dog might be sick

Dog looking sad and unwell lying on a grey sofa
(Image credit: Getty Images/Basak Gurbuz Derman)

Vomiting in dogs is very common, and it can be a sign of lots of things, from mild to serious. Some dogs will vomit once and then seem fine afterward, while others will vomit regularly. Some dogs will be fine all their lives and then become really ill with vomiting. The consistency of the vomitus and what it includes, as well as other symptoms your pet is experiencing, can all be clues as to what’s causing it.

I’ve been a vet for over eight years, and in that time, I’ve seen hundreds of cases of vomiting dogs. Some have just eaten something they shouldn’t have and are right as rain in a day or two, while for others, it’s the first sign of something more serious going on.

Below, we’ll go over what causes vomiting in dogs, and some of the common treatments your dog might need.

What are the causes of dog vomiting?

Vomiting is one of the most common symptoms dogs can experience, meaning there are lots and lots of potential causes. Some will be more or less likely depending on your dog’s age, personality, and other symptoms they’re experiencing, but in many cases, your vet will need to do testing to work out what’s wrong. Let’s look at some of the potential causes of vomiting in dogs so you can start figuring out what’s wrong.

1. Dietary indiscretion or sudden diet change

Dietary indiscretion is vet-speak for ‘eaten something they shouldn’t have’ whether it’s old pizza or next door’s cat poop. Sudden diet change can have the same effect. It usually comes with diarrhea and clears up after a couple of days. It’s not serious, as long as they don’t get too dehydrated in the meantime.

2. Allergies and intolerances

If your dog regularly vomits, has loose stools, itches, gets ear infections, or suffers from borborygmi (a rumbling stomach) then they might have a dietary allergy. Don’t just switch their diet though – you’ll need to do a proper diet trial under advice from your vet to get a diagnosis. To learn more about food allergies in dogs, this expert's guide can help.

3. Medication reactions

Vomiting can be due to a reaction to a new medication. If your pet has recently started a new medication, look at the package insert or call your vet to see if vomiting is a known reaction. Your vet will be able to advise whether your pet should continue the medication or not.

4. Bilious vomiting syndrome

With bilious vomiting, dogs who are otherwise well, vomit yellow, foamy fluid in the early hours of the morning or when they’ve not eaten for a while. It’s more common in dogs fed once a day and is thought to be related to nausea from having an empty stomach. Increasing feeding to twice daily usually solves the problem.

5. Motion sickness

Yes, dogs can get motion sick! If they show fear in the car, drool a lot, or vomit during or shortly after travel, then it’s probably motion sickness. You can talk to your vet about tablets for dog travel sickness, and some training to reduce car fear can help too.

Dog sitting in the car with its head rested on the back of a seat

(Image credit: Getty Images/snapshots are the best)

6. Worms and other parasitic infections

With heavy worm burdens or certain parasitic infections, dogs can vomit. You may see worms in the vomit, but an absence of worms doesn’t mean parasites aren’t the cause. Your vet can do a worm egg count or prescribe a wormer if worms are a likely cause of your dog’s vomiting. We've also written a helpful guide on how to treat a dog with worms.

7. Toxin ingestion

Dogs often eat things they shouldn’t, and toxic foods like chocolate and some mushrooms are no exception. Vomiting is one of the most common signs of poisoning in dogs, so if there’s a chance your dog could have gotten into something toxic, you should call your vet immediately to discuss. Here are 32 foods that dogs should never eat.

8. Bowel obstruction

A bowel obstruction caused by a foreign object (like a sock, mushed-up stick, or small ball) is another reason dogs might vomit. This one can be fatal if not treated, and it’s one of the reasons it’s always best to get a vet to take a look at your vomiting dog rather than risk it getting worse.

9. Pancreatitis

Pancreatitis in dogs is a relatively common cause of vomiting where the pancreas (a digestive organ) becomes inflamed. It’s very painful, and most dogs will feel very sorry for themselves, be off their food, and be vomiting. Dogs with suspected pancreatitis need treatment at a vet.

10. Liver or kidney problems

Kidney and liver problems are another cause of vomiting in dogs. You might also see diarrhea in dogs, drinking and urinating more, or inappetence alongside the vomiting. Again, this cause of vomiting in dogs needs vet attention, stat!

11. Parvovirus and other viral infections

Many viral infections can cause vomiting, including the three we vaccinate against most – parvovirus, hepatitis, and distemper. If your dog’s vaccinations are incomplete or are overdue, it’s important to consider one of these three viral infections as potential causes of dog vomiting.

12. Cancer

Unfortunately, cancer is always a potential cause of just about any symptom. Tumors in the GI tract causing blockages, tumors producing hormones causing nausea, and tumors causing pancreas, kidney or liver problems are all strong candidates for dogs vomiting in their senior years.

When should you be concerned about your dog throwing up?

In general, it’s best to take your dog to your vet for vomiting if they:

  • Are depressed, lethargic or unwell in themselves
  • Can’t keep food or water down
  • Are under 12 months old
  • Have been vomiting for more than 24 hours
  • Have other symptoms that are concerning for some of the more serious diseases listed above
  • Are not fully vaccinated

Dog lying down sideways on a fluffy rug looking sad

(Image credit: Getty Images/alex_ugalek)

Of course, I can’t cover every eventuality, so I always advise you to schedule a visit with your vet if you are concerned for any reason – your gut instinct is often reliable in these cases!

How is vomiting in dogs diagnosed?

Your vet will take your pet’s history by asking you questions like how long the vomiting has gone on for, any other symptoms your pet has, and what they’re behavior is like at home. They’ll then perform a clinical exam, which is where they’ll check your dog over - looking at their gums, checking for dehydration, and feeling their abdomen.

Depending what they note, they might recommend testing. Blood tests are usually a good place to start, with imaging (ultrasound or x-ray) a common second. The results might find an answer or they might need even more tests, but your vet will advise you of each stage as they go. In some cases, even with testing, the cause of your dog’s illness won’t be found – this can be frustrating, but as long as your dog is recovering then it isn’t usually something to worry about.

How to treat vomiting in dogs

It’s not a good idea to treat vomiting in dogs at home unless you’re 100% confident the cause was dietary indiscretion and your dog is healthy, not dehydrated, and not unwell in themselves.

In this case, you can continue to offer little and often food (stick to their usual diet to avoid further upset or tempt them to eat with a small piece of cooked boneless chicken) and wait out the vomiting, looking out carefully for signs of deterioration. Outdated advice often says to starve your dog for 24 hours before offering food again – this is no longer recommended.

Otherwise, it’s best to head to a vet, who will advise on appropriate treatment. Your dog might be given an injection to stop them vomiting and help them feel less nauseous.

If the vomiting is more severe, they may need to be hospitalized for an intravenous drip, antibiotics, pain relief, and anti-vomiting medications. Again, your vet will be happy to explain their advice at every stage.

Vomiting in dogs is one of the most common symptoms we vets see, and it has a lot of potential causes. In general, it’s best to see your vet for help working out what’s causing your dog’s vomiting, as so many of the conditions are serious. Your vet will be happy to explain their testing and treatment recommendations as they go.

You might also be wondering: Is my dog sick? and Can dogs get sick from humans?

Earth Rated Dog Wipes

Earth Rated Dog Wipes
If your dog is feeling unwell, you might want to have some dog wipes to hand. These ones by Earth Rated are unscented, hypoallergenic and free from alcohol and parabens.

Dr Joanna Woodnutt MRCVS

After graduating as a veterinarian from the University of Nottingham, Dr Joanna Woodnutt went on to practice companion animal medicine in the Midlands. She quickly developed a love of consulting and helping clients with medical problems such as dermatology, behaviour and nutrition - anything that involved helping clients understand their pets better. Jo started writing about pet health in 2017, realising that it meant she could help even more pet parents. Since then, she has written for countless online and print publications and is a regular contributor for Edition Dog Magazine. Jo now lives in the Channel Islands with her husband Ian and terrier Pixie, and they are expecting their first child very soon.