Dogs cannot explain that their stomach hurts, their joints feel stiff, or they are struggling to breathe. Instead, they communicate discomfort through small changes in behaviour, appetite, movement, sleep, and body language.
Some symptoms are obvious, such as repeated vomiting or a serious wound. Others are much easier to miss. A normally playful dog may become unusually quiet, refuse a favourite treat, drink more water, hide from family members, or hesitate before climbing the stairs.
Recognising the signs your dog may be unwell does not mean diagnosing the problem yourself. Many illnesses produce similar symptoms, and even minor-looking changes can occasionally indicate something serious.
The safest approach is to notice what is different, record when it started, and contact your veterinary practice when you are concerned.
This guide covers common dog illness symptoms, subtle warning signs, and situations that require urgent veterinary attention. Knowing your dog’s usual routine is one of the most valuable tools you have.
Know What Is Normal for Your Dog
Every dog behaves differently. One may spend most of the afternoon asleep, while another follows its owner around the house and expects several energetic play sessions.
Because of these differences, illness is often easier to recognise as a change from normal rather than a single universal symptom. Pay attention to your dog’s usual appetite, thirst, toilet habits, energy, breathing, movement, and social behaviour.
For example, sleeping after a long walk may be perfectly normal. Sleeping throughout the day, refusing to play, and moving unusually slowly could indicate lethargy.
PDSA explains that lethargic dogs may sleep more, move slowly, and lose interest in walks or games, although the possible causes range from mild to serious.
Regular grooming also gives you a chance to notice lumps, sore areas, skin changes, parasites, or sensitivity. You do not need to perform a medical examination – simply become familiar with how your dog normally looks and feels.
Changes in Appetite, Thirst, or Weight
Many owners first realise something is wrong when their dog ignores a meal. Missing one meal does not always signal an emergency, especially if the dog remains alert and comfortable, but ongoing loss of appetite deserves attention.
Watch for difficulty chewing, dropping food, eating much more slowly, or approaching the bowl and then backing away. These behaviours may be connected to dental pain, nausea, swallowing problems, stress, or another medical condition.
Increased appetite can also be important, particularly when accompanied by weight loss. Similarly, suddenly drinking much more or less water than usual may indicate an underlying health problem.
Try to measure unusual changes rather than relying on memory. Note how much food remains in the bowl, how often you refill the water, and whether your dog’s body shape or weight appears different.
Contact your vet if an appetite or thirst change continues, happens alongside vomiting or weakness, or affects a puppy, elderly dog, or animal with an existing medical condition.
Vomiting, Diarrhoea, and Toilet Changes
An isolated digestive upset can sometimes happen after a dog eats something unusual. However, repeated vomiting, persistent diarrhoea, blood, abdominal discomfort, or an inability to keep water down should not be ignored.
Blue Cross advises contacting a vet when a dog vomits repeatedly, has ongoing diarrhoea, or is especially vulnerable because it is very young, elderly, or already unwell. Vomiting and diarrhoea can occasionally be linked to poisoning, infection, obstruction, or another serious condition.
Changes in stool colour can also provide useful information. Fresh red blood, black sticky faeces, severe watery diarrhoea, or frequent straining all justify veterinary advice.
Vets Now recommends calling a vet when diarrhoea is severe, contains blood, lasts more than 24 hours, or occurs with lethargy or frequent vomiting.
Urination matters too. Look for accidents indoors, passing very small amounts, straining, crying while urinating, blood in the urine, or needing to go outside far more often than usual.
Never give human stomach medicine, painkillers, or leftover veterinary medication without professional guidance. Some common human medicines are dangerous for dogs.
Low Energy and Behavioural Changes
A sudden personality change can be one of the earliest signs your dog may be sick. A friendly dog may avoid contact, while a calm animal may become restless, irritable, or unable to settle.
Dogs in discomfort may hide, stare at one area of their body, lick themselves repeatedly, or resist being touched. Some become unusually clingy, while others move away from their owners.
Growling does not always mean a dog has developed a behavioural problem. If a normally tolerant pet suddenly growls when handled, pain or fear may be contributing. Give the dog space and arrange veterinary advice rather than punishing the warning.
Older dogs should not automatically be dismissed as “just slowing down.” The RSPCA notes that behavioural changes in senior dogs may reflect underlying health issues rather than ageing alone.
Record unusual behaviour on your phone and note when it occurs. A short video of pacing, trembling, coughing, or abnormal movement can be extremely useful if the behaviour stops before the veterinary appointment.
Pain, Limping, and Difficulty Moving
Dogs often hide pain surprisingly well. Warning signs may include limping, stiffness after rest, trembling, reluctance to jump, difficulty standing, or refusing to use the stairs.
A dog in pain may also pant, sleep in an unusual position, protect part of its body, cry, or become sensitive when touched. Blue Cross explains that changes in posture, movement, sleep, grooming, temperament, and breathing can all be connected to discomfort.
Do not force a limping dog to walk in order to “test” the leg. Limit activity and contact your vet, especially if the animal cannot place weight on the limb, has obvious swelling, or appears distressed. PDSA recommends immediate veterinary attention when a dog is in severe pain or cannot put a leg down.
Be careful when moving an injured animal. Even a gentle dog may bite when frightened or hurting, so avoid pressing, bending, or repeatedly examining a painful area.
Breathing, Eyes, Skin, and Physical Appearance
Abnormal breathing is one of the most important signs to recognise. Warning signs include rapid or shallow breaths, noisy breathing, excessive panting at rest, nostril flaring, coughing, or using the abdomen heavily with every breath.
A dog struggling to breathe may stretch its neck forward or hold its elbows away from its body. Vets Now lists open-mouth breathing, congestion, rapid breathing, coughing, and exaggerated chest or abdominal movement among the signs of breathing difficulty.
Check the eyes for redness, cloudiness, swelling, discharge, injury, or frequent blinking. Holding an eye closed usually suggests discomfort and requires veterinary advice because eye problems can worsen quickly.
Skin and coat changes may include persistent scratching, hair loss, scabs, redness, unusual odour, swelling, or a new lump. Not every lump is cancerous, but it is impossible to identify one safely by appearance alone.
Also look at the gums. Healthy gum colour varies between dogs, but gums that suddenly appear very pale, white, grey, or blue can indicate a serious problem, particularly when combined with weakness or breathing difficulty.
Emergency Signs That Need Immediate Veterinary Help
Some symptoms should not be monitored at home while waiting to see whether they improve. Contact a veterinary practice or emergency provider immediately if your dog:
- Is struggling to breathe or has blue, grey, or white gums
- Collapses, becomes unresponsive, or cannot stand
- Has a seizure lasting several minutes or repeated seizures
- Has a suddenly swollen, painful abdomen
- Experiences heavy bleeding or major trauma
- Repeatedly tries to vomit without producing anything
- May have eaten poison, medication, or a foreign object
- Shows severe pain, extreme weakness, or rapid deterioration
PDSA advises taking a pet to the vet immediately when it cannot breathe, has collapsed, develops white, grey, or blue gums, or is becoming worse quickly. Calling ahead allows the practice to prepare for the animal’s arrival.
Suspected poisoning also requires immediate advice, even when the dog still looks normal. Symptoms may be delayed, and the RSPCA warns that poisoning can cause vomiting, diarrhoea, unusual behaviour, pale gums, seizures, lethargy, or collapse.
Do not make your dog vomit unless a veterinary professional specifically instructs you to do so. Take the product packaging, plant sample, medication container, or a photograph with you when it is safe.
What to Tell Your Vet
Useful information can help the veterinary team assess urgency. Explain when the problem began, whether it is getting worse, and how your dog’s eating, drinking, urination, and bowel movements have changed.
Mention any recent injuries, diet changes, travel, tick bites, medication, access to rubbish, or possible exposure to toxins. Bring photographs, videos, packaging, or a fresh stool sample when the practice requests one.
Never worry that you are wasting the vet’s time. A telephone assessment may establish that monitoring is reasonable, but it may also identify a problem that needs prompt treatment.
The most common signs your dog may be unwell include appetite changes, unusual thirst, vomiting, diarrhoea, lethargy, behavioural changes, limping, pain, abnormal breathing, and changes to the eyes, skin, or toilet habits.
One mild symptom does not always mean your dog has a serious illness. However, persistent, worsening, or combined symptoms deserve professional advice, especially in puppies, senior dogs, and animals with existing conditions.
Learn your dog’s normal routine, record anything unusual, and keep your veterinary practice’s daytime and emergency numbers accessible.
When something feels wrong, contact your vet rather than attempting to diagnose or medicate your dog at home. Acting early can make treatment simpler and give your companion the best chance of recovering comfortably.