Why Is My Dog Being Sick? Causes and When to Worry

Dogs are sick fairly often — they explore the world with their mouths and aren't always fussy about what they eat — so a one-off vomit in an otherwise happy, bright dog is usually nothing serious. But vomiting can also signal something that needs urgent attention, so it really pays to know what to look for.

This is general guidance, not a substitute for veterinary advice — if you're worried about your dog, contact your vet.

Vomiting versus regurgitation

It's worth knowing the difference, as it helps your vet. Vomiting is an active process — there's heaving and effort, often preceded by drooling or lip-licking, and it brings up partly digested food or yellow bile. Regurgitation is passive — food simply comes back up effortlessly soon after eating, usually undigested and tube-shaped, with no heaving. Both are worth mentioning to your vet, because the causes are quite different.

Common causes

Mild, occasional vomiting often comes from:

• Eating too fast, too much, or something they shouldn't have (dietary indiscretion — bin raids being a classic).
• A sudden change of food.
• Mild tummy upsets and minor infections.
• Travel sickness in some dogs.

More concerning causes can include toxins (such as certain foods, plants or household products), foreign objects like a swallowed toy, sock or bone causing a blockage, parasites, and a range of underlying illnesses. That's exactly why persistent or severe vomiting always needs checking rather than waiting out.

What you can do at home

For a single vomit in an otherwise bright, well adult dog:

• Remove food for a few hours to let the stomach settle, but keep fresh water available — though don't let your dog gulp a huge amount all at once, as that can trigger more vomiting.
• Reintroduce small amounts of a bland, easily digestible food, then return to their normal diet gradually if everything stays settled.
• Use our can my pet eat this tool if you suspect they've eaten something they shouldn't.
• Don't give human anti-sickness medicines, which aren't designed for dogs.
• Don't fast puppies, and don't repeatedly withhold food from any dog without veterinary advice.

If diarrhoea is also present, see our dog diarrhoea guide, as the two often go together.

Common things that upset a dog's stomach

Knowing the usual triggers helps you prevent repeat episodes. Eating too quickly is a big one — gulping food and air can bring a meal straight back up, and a slow-feeder bowl often helps. Sudden diet changes are another frequent culprit, so always switch foods gradually over about a week. Rich, fatty human food and table scraps upset many dogs, as do raids on the bin or food bag. On walks, scavenging anything from rotting scraps to compost is a classic cause of a sudden upset. Some dogs are prone to travel sickness in the car, which usually settles once the journey ends but can be managed with your vet's advice if it's frequent. And, importantly, a number of everyday foods and household items are genuinely toxic to dogs and can cause vomiting among other serious signs — so if you think your dog has eaten something they shouldn't, don't wait to see how it goes; check with your vet straight away. Keeping food, bins and hazards out of reach prevents a surprising amount of trouble.

When to see a vet

Contact your vet promptly — and seek emergency help for severe signs — if:

• Your dog is vomiting repeatedly, can't keep even water down, or is retching and trying to be sick without bringing anything up. This last sign, especially alongside a bloated, hard tummy and restlessness, can be a serious emergency.
• There's blood in the vomit, or it looks like coffee grounds.
• Your dog is lethargic, weak, in pain, has a swollen or hard tummy, or seems generally unwell.
• You suspect a swallowed object, or that they've eaten something toxic.
• It's a puppy, an elderly dog, or a dog with another health condition — these dogs need quicker action as they dehydrate faster.
• The vomiting lasts more than 24 hours or keeps recurring.

When in doubt, phone your vet — they'd far rather you checked than waited. Find a practice via our vets directory, and plan for unexpected costs with the pet emergency cost calculator and our pet insurance guide.

The takeaway

A one-off vomit in a bright, otherwise well dog is rarely cause for alarm, and a short rest from food with water available usually does the trick. What matters most is staying alert to the warning signs — repeated vomiting, blood, a bloated tummy, lethargy, suspected poisoning or a swallowed object, or a poorly puppy or senior — and acting fast when you see them. Keeping bins, hazards and toxic foods out of reach prevents a lot of trouble, and a quick browse of safe chews and slow-feeder bowls in our shop can help too. When in doubt, phone your vet.

Sources

• PDSA — Pet Health Advice
• Blue Cross — Pet Advice
• RSPCA — Dogs