Common Signs of Illness in Dogs: When to See a Vet

For everything else, this guide organizes common warning signs by how urgently they typically call for veterinary attention. It's general information, not a diagnosis — only a veterinarian who has examined your dog can tell you what's actually going on, and a symptom on this list is a reason to get your dog checked, not a confirmation of any specific condition.

How to use this list

Dogs can't tell you what's wrong, and the same symptom (say, vomiting) can mean anything from "ate something disagreeable yesterday" to something serious. Context matters: how long it's been going on, whether it's a single episode or repeated, and whether other symptoms are present alongside it. When in doubt, calling your vet's office to describe what you're seeing is always a reasonable step — they can help you judge urgency over the phone.

Urgent: contact an emergency vet now

According to guidance from Texas A&M's College of Veterinary Medicine, the following warrant immediate care rather than waiting for a routine appointment:

This list draws on Texas A&M Veterinary Medicine's "Recognizing a Pet Emergency" and "When to Call a Veterinarian" guidance. It is not exhaustive — any symptom that feels severe or is rapidly worsening deserves an urgent call, even if it isn't listed here.

Soon: book an appointment in the next day or two

These signs usually aren't immediately life-threatening but generally shouldn't wait for your next annual exam:

• A single bout of vomiting or diarrhea that resolves quickly is often not urgent on its own, but repeated episodes over a day or two, or vomiting/diarrhea combined with lethargy or loss of appetite, is worth a prompt visit.
• Noticeable lethargy or reduced interest in normal activities lasting more than a day.
• Limping or reluctance to bear weight on a leg, if it doesn't resolve within a day or worsens.
• Increased thirst and urination beyond your dog's normal pattern.
• Persistent coughing, sneezing, or nasal discharge, especially if it continues for more than a couple of days.
• Scratching, licking, or chewing at one area intensely enough to cause redness, hair loss, or a hot spot.
• Noticeable weight loss or gain without a clear cause.
• A lump or swelling that's new or changing.

Worth mentioning at your next routine visit

Some changes are more about "keep an eye on it and tell your vet" than "go right now":

• Mild changes in sleep patterns, especially in senior dogs.
• Slightly increased or decreased appetite that isn't dramatic and doesn't come with other symptoms.
• Occasional, mild stiffness after exercise in an older dog.
• Bad breath (which is also a common sign of dental disease — see our guide to dog dental care for prevention and cost information).
• Gradual changes in body condition (see our guide on telling if your dog or cat is overweight).

A note on why context matters

The same symptom can point in very different directions depending on your dog's age, breed, and history — that's part of why this article gives general categories rather than a diagnosis. A young, otherwise healthy dog with one vomiting episode is a different situation than a senior dog with diabetes doing the same thing. If you're ever unsure which category a symptom falls into, treat it as "soon" rather than "monitor," and don't hesitate to call your vet's office to ask — most clinics are used to these calls and can help you triage over the phone.

FAQ

My dog vomited once but is acting completely normal otherwise — should I be worried? A single episode of vomiting in an otherwise normal, active dog is often not an emergency, but it's still worth watching for a repeat episode or other symptoms over the next 12–24 hours, per Texas A&M's guidance. If it happens again, or your dog seems off in any other way, call your vet.

Is it normal for older dogs to sleep more and slow down? Some reduction in activity is a normal part of aging, but a sudden or significant change — rather than a gradual one — is worth mentioning to your vet, since it can also be a sign of pain, a treatable illness, or cognitive changes.

How much does a vet visit typically cost if I do need to go in? Costs vary by clinic, region, and whether it's a routine exam or an emergency — see our guide to vet visit costs for a fuller breakdown.

Veterinary disclaimer: This article is for general educational purposes only and is not a substitute for professional veterinary diagnosis, examination, or treatment. It cannot tell you what's wrong with your specific dog. If your dog is showing any of the urgent signs listed above, contact an emergency veterinarian immediately rather than relying on this or any other article.