The signs your dog is sick are not always dramatic. Sometimes the first clue is simply that your dog seems quieter than usual, leaves breakfast unfinished, drinks more water, starts hiding, or no longer wants to play.
Other symptoms are much easier to recognize. Repeated vomiting, severe diarrhea, trouble breathing, collapse, seizures, a swollen abdomen or uncontrolled bleeding can require urgent veterinary care.
The key is knowing what is normal for your dog and noticing meaningful changes early.
How Can You Tell if Your Dog Is Sick?
Start with what is normal for your own dog.
Dogs differ in appetite, activity, sleep patterns, bowel habits and personality. Therefore, a sudden change from your dog’s normal routine can sometimes matter more than one isolated symptom.
Pay attention to changes in:
- Appetite
- Water intake
- Energy level
- Sleep
- Behavior
- Breathing
- Walking and movement
- Vomiting or stool
- Urination
- Body weight
- Skin and coat
- Ears and eyes
- Pain or sensitivity to touch
Dog Illness Warning Signs at a Glance
| What You Notice | What to Do |
|---|---|
| Mild change that quickly resolves | Monitor closely if your dog otherwise seems comfortable, alert and normal. |
| Persistent appetite, digestive, skin, ear, mobility or behavior change | Arrange veterinary advice, especially if the problem is worsening or keeps returning. |
| Repeated vomiting or severe diarrhea | Contact a veterinarian promptly because dehydration and serious disease are possible. |
| Blood in vomit, stool or urine | Contact a veterinarian promptly. Black, tarry stool is particularly concerning. |
| Difficulty breathing | Seek emergency veterinary care. |
| Collapse, severe weakness or unresponsiveness | Seek emergency veterinary care. |
| Seizure | Contact a veterinarian immediately. Ongoing or repeated seizures are an emergency. |
| Swollen abdomen with repeated retching | Seek emergency care immediately because gastric dilatation-volvulus may be possible. |
| Major trauma, severe bleeding or suspected poisoning | Seek urgent or emergency veterinary care immediately. |
1. Your Dog Is Much Less Active Than Normal
Dogs often become quieter when they do not feel well.
You may notice that your dog:
- Sleeps more than usual
- Does not greet you normally
- Stops asking to play
- Walks slowly
- Does not want to go outside
- Seems weak or unusually tired
A quiet day after heavy exercise may not mean illness. However, unexplained lethargy can occur with pain, infection, digestive disease, anemia, heart problems and many other conditions.
If the change is significant, persists or occurs with another symptom, contact your veterinarian.
2. Your Dog Stops Eating or Has a Major Appetite Change
Loss of appetite can be one of the earliest signs that something is wrong.
Possible causes range from nausea and dental pain to infection, digestive disease, pain elsewhere in the body or systemic illness.
Watch for:
- Completely refusing food
- Eating much less than normal
- Taking food but dropping it
- Difficulty chewing
- Walking away from meals
- Suddenly becoming unusually hungry
AAHA notes that reduced food or water intake can also occur with pain. A persistent appetite change deserves veterinary attention, particularly when it lasts more than a day or occurs with other symptoms.
3. Your Dog Is Drinking Much More or Less Than Normal
Changes in thirst can provide an important clue.
Increased drinking may occur with:
- Hot weather or increased exercise
- Kidney disease
- Diabetes
- Cushing’s syndrome
- Some medications
- Other metabolic conditions
On the other hand, a dog that feels nauseated or seriously ill may drink less than usual.
Do not deliberately restrict water from a dog that appears unusually thirsty unless a veterinarian specifically instructs you to do so.
4. Vomiting
One isolated vomiting episode does not always mean a dog is seriously ill. However, repeated vomiting can quickly become more concerning.
Contact a veterinarian sooner if vomiting occurs with:
- Blood
- Weakness
- Abdominal pain
- Loss of appetite
- Diarrhea
- Dehydration
- Possible toxin exposure
- Possible foreign-object ingestion
For a complete guide, read: Why Is My Dog Vomiting? Common Causes and Warning Signs .
5. Diarrhea
Loose stool can occur after a mild diet upset, stress or a sudden food change. However, diarrhea can also occur with parasites, infections, toxins, pancreatitis and intestinal disease.
Warning signs include:
- Very frequent watery diarrhea
- Fresh blood
- Black or tarry stool
- Vomiting at the same time
- Weakness
- Poor appetite
- Dehydration
- Persistent or recurring diarrhea
For more detail, see: Diarrhea in Dogs: When to Worry and What to Do .
6. Changes in Urination
Changes in how often, how much or how comfortably a dog urinates deserve attention.
Watch for:
- Urinating much more often
- Producing unusually large amounts of urine
- Straining to urinate
- Repeated attempts with little urine produced
- Blood in the urine
- Accidents in a previously house-trained dog
- Crying or showing pain while urinating
- Suddenly drinking much more water
7. Coughing or Changes in Breathing
A cough can occur with respiratory infections, airway problems, heart disease and other conditions.
You may also notice:
- Rapid breathing at rest
- Noisy breathing
- Wheezing
- Persistent coughing
- Excessive panting without an obvious reason
- Difficulty settling because of breathing discomfort
Breathing problems should not be monitored casually at home when the dog is clearly struggling.
8. Pale, Blue, Grey, Yellow or Unusually Red Gums
Healthy gum color varies somewhat between individual dogs, and some dogs naturally have dark pigmentation.
However, a sudden change in normally pink areas can be important.
Concerning colors can include:
- Very pale or white: may occur with anemia, blood loss, poor circulation or shock
- Blue, grey or purple: can indicate inadequate oxygen
- Yellow: can occur with jaundice
- Unusually bright or dark red: may occur with several serious conditions, including heat-related illness
9. Unexplained Weight Loss
Gradual weight loss can be easy to miss under a thick coat.
Possible causes include:
- Reduced calorie intake
- Dental problems
- Intestinal disease
- Parasites
- Diabetes
- Kidney disease
- Liver disease
- Cancer
- Other chronic illnesses
Unexpected weight loss should be investigated even when the dog still seems active.
10. Unexpected Weight Gain or Loss of Normal Body Shape
Weight gain can also signal a problem.
Sometimes the cause is simply excess calorie intake. However, reduced activity, hormonal disease, medications and other conditions can contribute.
Use body shape as well as scale weight.
For a full guide, read: How to Tell if Your Dog Is Overweight .
11. Limping, Stiffness or Difficulty Moving
Dogs do not always cry when they are in pain.
Instead, you may notice:
- Limping
- Stiffness when standing up
- Difficulty climbing stairs
- Reluctance to jump
- Walking more slowly
- Protecting one leg
- Not wanting to be touched
- Restlessness or difficulty getting comfortable
Pain can result from arthritis, muscle injury, ligament damage, back problems, broken bones and many other conditions.
AAHA also recognizes changes in appetite, posture, movement and behavior as possible signs of pain.
12. Sudden Behavior or Personality Changes
A dog that suddenly becomes withdrawn, unusually fearful, restless or aggressive may be uncomfortable or ill.
Behavior changes can occur with:
- Pain
- Neurological disease
- Vision or hearing problems
- Hormonal or metabolic disease
- Toxin exposure
- Cognitive changes
- Other medical problems
Therefore, do not automatically label a sudden personality change as a training problem.
A veterinary examination can help rule out physical causes first.
13. Skin Changes, Persistent Itching or Hair Loss
Skin problems can cause much more discomfort than they appear to from the outside.
Watch for:
- Constant scratching
- Paw licking
- Hair loss
- Red skin
- Scabs
- Open sores
- Greasy skin
- Bad skin odor
- Lumps or swelling
Possible causes include allergies, fleas, mites, bacterial infection, yeast, fungal disease and other skin conditions.
For more information, read: Dog Skin Allergies: Common Signs and Causes .
14. Fleas, Ticks or Parasite Signs
Parasites can cause both obvious and subtle illness.
Fleas may lead to intense itching, flea allergy, tapeworm infection or anemia in severe infestations.
Ticks can transmit infectious diseases, while intestinal worms may cause diarrhea, weight loss, anemia or poor growth.
Read our detailed guides:
- Fleas and Ticks on Dogs: Signs, Prevention, and What to Do
- Worms in Dogs: Common Types, Symptoms, and Prevention
15. Ear Problems
Ear disease can cause significant pain.
Signs include:
- Head shaking
- Ear scratching
- Bad odor
- Redness
- Discharge
- Pain when the ear is touched
- Repeated ear problems
Allergies, yeast, bacteria, mites and foreign bodies can all contribute.
For a complete guide, see: Dog Ear Infections: Signs, Causes, and When to See a Vet .
16. Eye Changes
Eye problems can worsen quickly, so do not ignore sudden changes.
Watch for:
- Squinting
- Keeping one eye closed
- Redness
- Cloudiness
- Excessive tearing
- Thick discharge
- Eye swelling
- Rubbing or pawing at the eye
- Sudden vision problems
17. Nose or Respiratory Discharge
An occasional sneeze is usually not alarming.
However, persistent sneezing or nasal discharge may occur with infection, irritation, foreign material, dental disease or other problems.
Contact your veterinarian if you notice:
- Persistent thick nasal discharge
- Blood from the nose
- Difficulty breathing through the nose
- Facial swelling
- Persistent coughing at the same time
- Loss of appetite or lethargy
18. A Swollen or Painful Abdomen
A suddenly enlarged abdomen is not something to ignore.
Possible causes include gas, fluid accumulation, internal bleeding, organ enlargement and gastric dilatation-volvulus, commonly called GDV or bloat.
GDV is particularly urgent.
Signs may include:
- Repeated unsuccessful attempts to vomit
- Retching
- Drooling
- Restlessness
- A swollen or tight abdomen
- Pain
- Pale gums
- Weakness
- Collapse
19. Seizures, Tremors or Sudden Neurological Changes
Neurological symptoms can be frightening and may require urgent care.
Signs include:
- Seizures
- Sudden loss of balance
- Falling
- Walking in circles
- Severe tremors
- Head tilt
- Sudden weakness
- Loss of consciousness
- Severe disorientation
20. Collapse or Unresponsiveness
Collapse is always a serious warning sign.
Possible causes include:
- Shock
- Severe blood loss
- Heart disease
- Low blood sugar
- Heatstroke
- Poisoning
- Neurological disease
- Other severe illness
21. Severe Bleeding or Major Injury
Obvious trauma requires prompt attention, but internal injuries are not always visible.
Seek urgent veterinary care after:
- Being hit by a vehicle
- A serious fall
- A major animal attack
- Deep wounds
- Suspected broken bones
- Severe or uncontrolled bleeding
- Chest or abdominal trauma
A dog may initially appear surprisingly normal because stress hormones can temporarily mask pain and weakness.
22. Suspected Poisoning
Do not wait for symptoms when you know or strongly suspect that your dog has eaten something toxic.
Potential hazards include:
- Human medications
- Rodent poison
- Antifreeze
- Chocolate
- Xylitol-containing products
- Grapes and raisins
- Some plants
- Household chemicals
- Recreational or prescription drugs
Signs of Illness in Puppies
Puppies can become dehydrated, weak or seriously ill faster than healthy adult dogs.
Use a lower threshold for contacting your veterinarian if a puppy develops:
- Repeated vomiting
- Diarrhea
- Blood in stool
- Refusal to eat
- Weakness
- Extreme sleepiness
- Difficulty breathing
- A swollen abdomen
- Seizures
- Rapidly worsening symptoms
Vaccination is also an important part of preventing several serious infectious diseases.
See: Dog Vaccination Schedule: What Vaccines Does Your Dog Need? .
Signs of Illness in Senior Dogs
Older dogs may show illness through subtle changes rather than dramatic symptoms.
Watch for:
- Weight loss
- Increased thirst
- More frequent urination
- Reduced appetite
- Difficulty rising
- New limping or stiffness
- Muscle loss
- Behavior changes
- Confusion
- Recurring digestive problems
- New lumps or swelling
Do not assume every change is simply “old age.” Many age-related health problems can be treated or managed more effectively when found early.
How to Check Your Dog at Home
A short daily health check can help you notice problems early.
Look at:
- Behavior: Is your dog acting normally?
- Appetite: Did your dog eat normally?
- Water: Has drinking changed noticeably?
- Breathing: Is breathing comfortable and quiet at rest?
- Movement: Is your dog walking normally?
- Stool: Is bowel movement normal?
- Urine: Is your dog urinating normally?
- Skin and coat: Are there new sores, itching or lumps?
- Eyes and ears: Is there redness, discharge, odor or pain?
- Body condition: Has weight or body shape changed?
You do not need to perform a medical examination every day. The goal is simply to become familiar with your dog’s normal patterns.
What Information Should You Tell Your Veterinarian?
A clear history helps your veterinarian decide what to investigate.
Try to note:
- When the symptoms started
- Whether they are getting better or worse
- Changes in appetite
- Changes in water intake
- Vomiting or diarrhea
- Changes in urination
- Possible toxin exposure
- Possible foreign-object ingestion
- New foods or treats
- Recent travel
- Current medications
- Vaccination status
- Parasite prevention
- Recent injuries
- Any previous similar episodes
When Can You Monitor Your Dog at Home?
A very mild, short-lived change may sometimes be monitored if your dog remains bright, comfortable, interested in food and water, and otherwise normal.
However, home monitoring becomes less appropriate when:
- Symptoms keep returning
- More than one symptom is present
- Your dog is getting worse
- Your dog appears painful
- Your dog is very young or elderly
- Your dog has an existing medical condition
- You suspect a toxin or swallowed object
When you are unsure, calling your veterinary clinic is safer than trying to diagnose the problem yourself.
Symptoms That Should Never Be Ignored
- Difficulty breathing
- Blue, grey or purple gums
- Collapse or unresponsiveness
- Severe weakness
- Ongoing or repeated seizures
- Severe or uncontrolled bleeding
- Major trauma
- Suspected poisoning
- A swollen painful abdomen
- Repeated retching without producing vomit
- Severe abdominal pain
- Inability to urinate
- Serious eye injury
- Rapidly worsening illness
Routine Veterinary Care Can Find Problems Earlier
Not every disease causes obvious symptoms at first.
Routine veterinary examinations can detect changes in body weight, heart or lung sounds, teeth, joints, skin and other areas before owners notice a major problem.
Merck Veterinary Manual recommends at least annual routine examinations for adult dogs. Puppies require more frequent visits during early life, while senior dogs often benefit from veterinary assessment at least twice yearly or more often when appropriate.
Preventive care can also include:
- Vaccination review
- Parasite prevention
- Dental assessment
- Weight and body-condition assessment
- Nutrition review
- Age-appropriate screening tests
Frequently Asked Questions
What are the first signs that a dog is sick?
Early signs can include reduced appetite, unusual tiredness, changes in drinking, hiding, less interest in play, vomiting, diarrhea, coughing or a change in normal behavior.
How do dogs act when they do not feel well?
Some dogs become quiet or withdrawn. Others appear restless, clingy or irritable. Because behavior varies between dogs, a noticeable change from your dog’s normal personality is often the most useful clue.
Is sleeping more a sign my dog is sick?
It can be. Dogs naturally sleep different amounts depending on age and activity. However, sudden unexplained lethargy or sleeping much more than normal can occur with illness or pain.
When should I worry if my dog stops eating?
Contact your veterinarian if appetite loss persists, your dog refuses both food and water, or reduced appetite occurs with vomiting, diarrhea, pain, weakness or another concerning symptom. Puppies and dogs with existing medical conditions may need attention sooner.
What gum color is an emergency in dogs?
Blue, grey or purple gums can indicate inadequate oxygen and require emergency care. Very pale or white gums together with weakness or collapse can also signal a serious problem.
Is vomiting always a sign of serious illness?
No. One isolated episode may be mild. However, repeated vomiting, blood, abdominal pain, weakness, dehydration, toxin exposure or possible foreign-object ingestion requires veterinary attention.
When is dog diarrhea serious?
Diarrhea becomes more concerning when it is severe or persistent, contains significant blood, looks black and tarry, occurs with vomiting, or causes weakness, poor appetite or dehydration.
Why is my dog suddenly hiding?
Some dogs hide when they feel pain, fear, nausea or general illness. Sudden unexplained hiding, especially with appetite or behavior changes, deserves closer attention.
How can I tell if my dog is in pain?
Pain signs can include limping, stiffness, reluctance to move, panting, restlessness, reduced appetite, unusual aggression, hiding or sensitivity when touched.
Can a dog be seriously sick but still wag its tail?
Yes. A wagging tail does not prove that a dog is healthy or pain-free. Dogs can still interact socially despite significant illness or discomfort.
Should I wait and see if my dog gets better?
For a very mild isolated change in an otherwise normal dog, brief monitoring may be reasonable. However, do not wait when symptoms are severe, worsening, persistent or associated with emergency warning signs.
Should I give my sick dog human medicine?
No. Do not give human painkillers, stomach medicines or other medication unless your veterinarian specifically recommends the product and dose for your dog.
The Bottom Line
The signs your dog is sick can range from subtle changes in appetite or behavior to obvious medical emergencies.
Knowing your dog’s normal routine makes it easier to recognize when something has changed. Reduced appetite, unusual tiredness, digestive problems, changes in drinking or urination, unexplained weight changes, pain, skin problems and recurring ear disease all deserve attention when they persist.
More serious signs require faster action. Difficulty breathing, collapse, seizures, severe bleeding, major trauma, suspected poisoning, abnormal gum color, inability to urinate, or a swollen abdomen with repeated retching should never be treated as a wait-and-see problem.
When you are uncertain, contact your veterinarian. Early assessment is often safer than waiting until a dog becomes obviously ill.
References and Further Reading
American Animal Hospital Association (AAHA)
Guidance on recognizing pet emergencies, breathing difficulty, persistent vomiting and diarrhea, abnormal gum color, seizures, abdominal swelling and sudden behavior changes.
American Animal Hospital Association (AAHA)
Guidance on recognizing common signs of pain in pets, including appetite, mobility and behavior changes.
Merck Veterinary Manual
Routine Health Care of Dogs — guidance on recognizing illness, routine examinations and age-appropriate veterinary care.
Merck Veterinary Manual
Evaluation and Initial Treatment of Dog and Cat Emergencies — guidance on breathing problems, shock, poisoning, seizures, major trauma and other emergency conditions.
VCA Animal Hospitals
Emergency and first-aid guidance for dogs, including trauma, GDV, poisoning, severe bleeding and respiratory emergencies.
