Causes of Fever in Dogs and How to Respond

ImmunitySymptomsMeongsiljang Veterinary Advisory Board

We’ve put together a guide on the causes of fever in dogs and how to respond at each stage. You can easily check the normal body temperature range and the signs that indicate an immediate trip to the vet.

What Constitutes a Fever in Dogs?

A veterinarian is taking a puppy’s temperature using a rectal thermometer.

A fever in dogs is an immune-mediated rise in core body temperature above the normal range of 37.5–39.2°C, specifically exceeding 39.5°C. The most critical factors are the exact temperature reading and how long it persists. If the temperature remains above 39.5°C for more than 24 hours or exceeds 40°C, infection or inflammation should be suspected, and immediate veterinary care is necessary. A dry nose or warm ears are not reliable indicators of fever. Accurate temperature measurement must always be taken using a rectal thermometer.

Assessing Urgency by Body Temperature Stage

The appropriate response depends on the body temperature reading. Use the table below to check your pet’s condition. Keep in mind that puppies under six months of age and senior dogs are at higher risk, even at the same temperature.

Urgency Criteria by Body Temperature

Item	Normal	Low-Grade Fever	Fever	High Fever
Temperature Range	37.5–39.2℃	39.2–39.5℃	39.5–40.0℃	40.0℃ or higher
Response	Daily care	Observe for 24 hours	Visit clinic same day	Immediate emergency care
Check for Accompanying Symptoms	Not needed	Check appetite & energy	Check for vomiting, diarrhea, coughing	Seizures or collapse = emergency

A dog's normal body temperature (37.5–39.2℃) is about 1–2.7℃ higher than a human's (36.5℃). For puppies under 6 months and senior dogs over 7 years, judge one level higher.

Checklist of Symptoms When Your Dog Has a Fever

When your pet has a fever, you’ll often notice several behavioral changes in addition to an elevated body temperature. Keep an eye out for the following signs: - Lethargy and weakness: Noticeably less active than usual, often lying down for extended periods. - Decreased appetite: Eating very little or refusing even favorite treats. - Rapid breathing: Breathing faster or panting more than usual as the body tries to cool down. - Shivering and hunching: Trembling as if cold and curling up in a corner. - Eye and nasal discharge: Increased eye crust or runny nose compared to normal. - Warm ears and belly: Feeling significantly hotter to the touch than usual.

A lethargic puppy curled up on a blanket.

Go to a 24-Hour Clinic Immediately If These Symptoms Occur

If your dog has a high fever above 40°C (104°F), or if the fever is accompanied by any of the following symptoms, it is an emergency: seizures or decreased consciousness, repeated vomiting or diarrhea, difficulty breathing or blue gums, blood in the urine or black stools, or severe lethargy to the point of being unable to stand. Heatstroke is especially dangerous; once body temperature exceeds 41°C (105.8°F), organ damage begins. Never give human fever reducers like Tylenol or ibuprofen, as they are toxic and can be fatal to dogs.

Main Causes of Fever in Dogs

Fever is not a disease in itself, but rather a signal that the body is fighting something. The causes can be broadly categorized into four types: - Infectious: Viruses such as parvovirus and distemper, bacterial enteritis, pyometra, pneumonia, etc. - Immune-mediated: Autoimmune diseases such as immune-mediated arthritis and lupus - Inflammatory: Organ inflammation such as pancreatitis, hepatitis, and otitis media - Neoplastic: Fever can also occur with certain tumors, such as lymphoma Veterinary internal medicine textbooks classify cases where the cause is difficult to identify as "Fever of Unknown Origin (FUO)" and recommend a stepwise approach using blood and imaging tests.

Diagnostic Process at the Clinic

When a dog is brought to the clinic with a fever, the veterinarian will investigate the cause in the following order: - History and Physical Examination: Review vaccination records, recent walking locations, dietary intake, and the health status of other pets in the household. - Blood Tests (CBC and Biochemistry): Assess white blood cell counts to determine the presence of infection or inflammation. - Imaging (X-rays and Ultrasound): Check for pyometra, pneumonia, or intra-abdominal inflammation. - Urinalysis and Fecal Examination: Differentiate urinary tract infections and parasitic infestations. - Additional Tests: If the cause remains unclear, further diagnostics such as CT scans or joint fluid analysis may be performed. Medication schedules and dosages are determined by the veterinarian based on the dog’s weight and underlying condition. Do not administer medication based on your own judgment.

A veterinarian examining a dog with a stethoscope in the clinic.

Home Care Methods and What Not to Do

If you need to buy a little time before heading to the clinic, you can help lower your pet’s body temperature using the following methods: - Lukewarm damp cloth: Gently wipe the armpits, groin, and paw pads (do not use cold water or ice). - Cool, well-ventilated area: Move your pet to a cool spot with good airflow. - Provide water: Ensure fresh water is always available for drinking. - Recheck temperature: Monitor rectal temperature every 30 minutes.

Strictly avoid: Human fever reducers (such as acetaminophen or ibuprofen), ice baths, force-feeding, or wrapping your pet in a blanket to induce sweating.

Additional Precautions by Breed and Age

Brachycephalic breeds (such as French Bulldogs, Pugs, and Shih Tzus) have a reduced ability to cool down due to Brachycephalic Obstructive Airway Syndrome (BOAS), making them at higher risk than other breeds even at the same body temperature. If their breathing becomes heavier than usual or their body temperature rises, it is best to visit a veterinary clinic early. Puppies and senior dogs are prone to rapid dehydration, so if a fever persists, prompt veterinary care is essential. If an unspayed female dog develops a fever after her heat cycle, pyometra should be suspected, and this requires an emergency visit to the hospital.

Routine Care Points to Prevent Fever

Fever can be largely prevented through vaccinations and routine care. - Regular comprehensive vaccinations: Protection against parvovirus, distemper, hepatitis, and parainfluenza - Heartworm and internal parasite preventatives: Administer consistently once a month - Teeth brushing and ear cleaning: Prevents chronic inflammation such as periodontal disease and otitis externa - Adjust summer walk times: Avoid walking between 10 a.m. and 4 p.m. to prevent heatstroke - Consider spaying or neutering: Helps prevent pyometra and prostate infections Knowing your pet’s normal body temperature and resting respiratory rate will help you detect warning signs more quickly.

A healthy puppy enjoying an early morning walk on the grass.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Does a dry nose in a puppy mean they have a fever?

No, the dryness of a pet's nose is not directly related to body temperature. A pet's nose can become dry after waking up or in a dry environment. For an accurate assessment, you should use a rectal thermometer.

Is it safe to give my pet even a small amount of human fever-reducing medication?

Absolutely not. Tylenol (acetaminophen) and ibuprofen can cause fatal liver and kidney damage, as well as gastrointestinal bleeding, in dogs. Always use only medications prescribed by a veterinarian.

How long should I keep wiping with a lukewarm, damp cloth?

Check the temperature every 30 minutes until it drops below 39.5°C. If the temperature does not decrease after 30 minutes, or if there is shivering or decreased consciousness, go to the hospital immediately.

Is it normal for a pet to develop a fever after vaccination?

A temporary rise in body temperature can occur as part of the immune response after vaccination. However, since the exact duration of post-vaccination fever varies depending on the individual pet’s condition, it is safest to contact the clinic where the vaccination was administered if a fever develops. If a fever exceeding 40°C persists or is accompanied by lethargy or decreased appetite, please seek veterinary care immediately.

My pet has a fever and isn’t eating. Should I force-feed them?

Forcing food can actually increase the risk of aspiration pneumonia. If your pet is drinking water well, a short fast of about a day is generally safe. However, if they refuse both food and water for more than 24 hours, they should be seen by a veterinarian.

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References

[1] Englar RE. Common Clinical Presentations in Dogs and Cats. Wiley/Blackwell, 2019.

[2] Nelson RW, Couto CG. Small Animal Internal Medicine, 6th Ed. Elsevier, 2020 — Chapter: Fever of Unknown Origin.

[3] Silverstein DC, Hopper K. Small Animal Critical Care Medicine, 3rd Ed. Elsevier, 2022 — Chapter: Hyperthermia and Fever.

[4] Ettinger SJ, Feldman EC. Textbook of Veterinary Internal Medicine, 8th Ed. Elsevier, 2017.