Understanding What Causes Fever in Dogs
When your dog feels warm to the touch or seems out of sorts, you might wonder if they have a fever. Fever in dogs means their body temperature is higher than normal. For canines, the typical range sits between 100°F and 102.5°F (38.1°C to 39.2°C)—a bit warmer than humans. Anything above 103°F counts as a fever, while temperatures at or above 106°F are dangerous and require immediate attention.
Common Causes of Fever in Dogs
Dogs develop fevers for many reasons. Sometimes it’s obvious—like after a vaccination—but often the cause is hidden inside the body. Here’s what can trigger a dog’s temperature to rise:
- Bacterial, viral, or fungal infections: These can occur anywhere—lungs, kidneys, brain, skin, urinary tract, or ears.
- Abscessed or infected tooth: Dental issues aren’t just painful; they can lead to fever.
- Infected bite, scratch, or wound: Even a small injury can become infected and cause systemic symptoms.
- Autoimmune or immune-mediated diseases: Sometimes the immune system attacks the body itself.
- Inflammation: General inflammation from various sources may result in fever.
- Cancer: Some cancers disrupt normal body processes and raise temperature.
- Vaccination: It’s common for dogs to run a low-grade fever for about 24–48 hours after receiving shots.
- Toxin ingestion: Certain plants, antifreeze, medications (especially human drugs), and foods unsafe for dogs can all trigger fever.
- Bone marrow disorders: Problems with blood cell production sometimes cause fevers.
- Unknown causes (Fever of Unknown Origin - FUO): Occasionally no clear reason is found despite testing.
The Signs Your Dog Might Have a Fever
You won’t always spot a thermometer reading right away—dogs show behavioral changes before their temperature spikes are noticed. Watch for these signs:
- Lethargy and decreased energy
- Lack of appetite
- Shivering
- Vomiting or diarrhea
- A warm or dry nose (not always reliable)
- Ears that feel hot
- Red or glassy eyes
- Coughing or panting more than usual
- A runny nose
- Stiffness or reluctance to move
- A fast heart rate or rapid breathing
- Evident dehydration
If you notice any significant shift in your dog’s activity level, alertness, eating habits, or bathroom routines—especially if combined with physical symptoms—it’s time to check their temperature.
The Right Way to Measure Your Dog’s Temperature
The only accurate way is with a digital rectal thermometer designed for pets. Lubricate the tip first; then gently insert it about an inch into your dog’s rectum while someone helps hold them still. Remove it once you get a reading. Veterinary ear thermometers are also an option but tend to be less reliable than rectal readings. Don’t trust nose temperature or moisture—it simply isn’t accurate for diagnosing fever.
You’ll want to know what’s normal for your own dog: record their baseline temperature at different times over several days when healthy since excitement and stress can cause fluctuations. A single high reading without other symptoms doesn’t always mean illness.
When Should You Call the Vet?
- If your dog’s temperature exceeds 103°F (39.4°C), contact your veterinarian right away.
- If it hits 106°F (41.1°C) or higher—or if severe symptoms like extreme lethargy, blood in stool/vomit, persistent vomiting, refusal to eat/drink, or neurological signs appear—seek emergency care immediately.
Caring for Your Dog at Home While Waiting for Advice
- If the fever is at least 103°F: Apply cool water with a towel on ears and paws; use a fan to help cool them down but stop once temperature drops below that threshold.
- Encourage small sips of water to prevent dehydration; never force water intake.
- Avoid giving human medications like acetaminophen (Tylenol), ibuprofen (Advil), etc.—these are toxic and could be fatal for dogs!
The Veterinary Approach: Diagnosis and Treatment
Your vet will likely start with a physical exam followed by tests such as bloodwork (CBC and serum biochemistry), urinalysis/cultures, imaging (X-rays/ultrasound), and sometimes specialized cultures depending on clues from symptoms. Treatment depends on what they find—antibiotics/antifungals for infections; fluids if dehydrated; immune-suppressive drugs if autoimmune disease is suspected; cancer therapy where appropriate. If no cause emerges (FUO), vets may try empirical treatment while monitoring progress closely.
The Outlook for Dogs With Fever
If the underlying cause is found quickly and treated appropriately most dogs recover well from fevers. Persistent high temperatures are dangerous—they need thorough diagnosis to avoid long-term harm like organ damage. Since dogs can’t tell us how they feel directly, careful observation combined with correct use of thermometers is crucial whenever you suspect illness.
If you ever feel unsure about your dog's health during a fever episode—even if symptoms seem mild—don't hesitate to reach out to your veterinarian for guidance tailored specifically to your pet's needs.
