How to Tell If Your Dog Has a Fever: 10 Signs, Causes & What to Do

Knowing how to tell if your dog has a fever can make the difference between catching a serious illness early and letting it progress. Unlike humans, dogs can’t tell you when they feel unwell — so recognizing the warning signs is entirely up to you. This guide covers everything you need to know: normal temperature ranges, how to tell if your dog has a fever without a thermometer, how to take your dog’s temperature safely at home, and when to call your vet.

Quick Reference: How to Tell If Your Dog Has a Fever

Here is a quick summary of how to tell if your dog has a fever before we dive into the full guide:

• Step 1: Use a rectal thermometer — the most reliable way to tell if your dog has a fever
• Step 2: Check for physical symptoms such as lethargy, warm ears, or dry nose to tell if your dog has a fever without a thermometer
• Step 3: Compare to the normal range (38.3°C–39.2°C) to tell if your dog has a fever or is within healthy limits
• Step 4: If above 39.4°C (103°F), contact your vet — this confirms how to tell if your dog has a fever and needs care

What Is a Normal Body Temperature for Dogs?

The first step to knowing how to tell if your dog has a fever is understanding what’s normal. A healthy dog’s normal body temperature ranges from 38.3°C to 39.2°C (101°F to 102.5°F). Any reading above 39.4°C (103°F) is considered a fever in dogs. A temperature above 41°C (106°F) is a life-threatening emergency requiring immediate veterinary care.

Before diving into the signs, it helps to understand why knowing how to tell if your dog has a fever early leads to better outcomes. The faster you detect a fever, the sooner your vet can identify the underlying cause.

10 Signs to Tell If Your Dog Has a Fever

Many owners wonder how to tell if your dog has a fever without a thermometer. While a thermometer is the only accurate way to confirm a fever, these 10 symptoms often appear alongside elevated temperature:

• Warm, dry nose — A consistently dry, hot nose (not just after waking) can indicate a fever, though this alone is not a reliable indicator
• Lethargy and weakness — Your dog seems unusually tired, reluctant to move, or disinterested in activities they normally enjoy
• Loss of appetite — Refusing food or water for more than 12–24 hours
• Shivering or shaking — Trembling despite normal room temperature
• Red or glazed eyes — Eyes may appear bloodshot or unusually glassy
• Warm ears — Ears that feel significantly warmer than usual to the touch
• Rapid breathing or panting — Panting at rest without obvious heat or exercise as cause
• Nasal discharge — Runny nose, especially with discolored mucus
• Vomiting or diarrhea — Especially when combined with other symptoms
• Coughing — May suggest an upper respiratory infection driving the fever

Important: None of these signs alone confirms a fever. The only reliable way to know how to tell if your dog has a fever is by using a rectal or ear thermometer. If you are unsure how to tell if your dog has a fever, always err on the side of caution and contact your vet.

How to Take Your Dog’s Temperature at Home

Taking your dog’s temperature is the most accurate way to tell if your dog has a fever. Follow these steps to tell if your dog has a fever at home safely. You’ll need a digital rectal thermometer — the same type used for babies — or a veterinary ear thermometer.

Rectal Method (Most Accurate)

1. Apply a small amount of petroleum jelly or water-based lubricant to the thermometer tip
2. Have a second person gently restrain your dog, or ask your dog to sit/lie down
3. Lift your dog’s tail and gently insert the thermometer about 2.5 cm (1 inch) into the rectum
4. Hold it in place until the thermometer beeps (usually 60 seconds)
5. Remove, wipe clean, and read the temperature
6. Reward your dog with a treat immediately afterward

Ear Thermometer Method

Ear thermometers designed for pets are less accurate than rectal thermometers but easier to use. Insert the probe deep into the horizontal ear canal and hold until it beeps. Note that ear infections or debris can affect the reading. Either method can help you tell if your dog has a fever accurately.

Never use a forehead thermometer on your dog — these are designed for human skin and will not give an accurate reading through fur.

Common Causes of Fever in Dogs

Understanding the cause helps your vet make a faster diagnosis. Here are the most common reasons your dog has a fever — and why knowing how to tell if your dog has a fever early makes treatment more effective:

Infections

Bacterial, viral, or fungal infections are the leading cause of fever in dogs and the most common reason you’d need to know how to tell if your dog has a fever. Common examples include:

• Urinary tract infections (UTIs) — Very common, especially in female dogs. Often accompanied by frequent urination or straining.
• Respiratory infections — Kennel cough, pneumonia, or canine influenza
• Infected wounds or abscesses — Especially after a bite or scratch from another animal. Skin infections are one of the most common triggers of fever in dogs and should never be left untreated.
• Tick-borne diseases — Lyme disease, ehrlichiosis, and Rocky Mountain spotted fever. Learn more about ticks in wooded areas and the signs to watch for in dogs.
• Parvovirus — A life-threatening viral disease, especially in unvaccinated puppies

Toxin Ingestion

Toxin ingestion is another reason you may need to quickly tell if your dog has a fever. Certain toxic substances can trigger a fever response in dogs. If you suspect your dog has eaten something poisonous, contact your vet or the ASPCA Animal Poison Control Center immediately.

Vaccinations

Knowing how to tell if your dog has a fever after vaccination is important. A mild fever within 24–48 hours of vaccination is a normal immune response and usually resolves on its own. Temperatures above 39.7°C (103.5°F) post-vaccine should be reported to your vet. Some dogs may also experience delayed skin reactions after vaccines — these are typically mild but worth monitoring.

Inflammatory Conditions

Immune-mediated diseases, lupus, and certain cancers can cause persistent or recurring fevers in dogs. Supporting your dog’s immune system with immune support supplements during seasonal changes may help reduce susceptibility.

Heat Stroke

Heatstroke is one case where you may need to tell if your dog has a fever-like temperature without it being a true fever. While technically not a fever (which is immune-mediated), heatstroke causes a dangerously elevated body temperature and is a medical emergency. It can occur after being left in a hot car, excessive exercise in heat, or lack of shade and water.

When to Call Your Vet

If you’re trying to tell if your dog has a fever, contact your veterinarian right away if your dog:

• Has a temperature above 39.4°C (103°F)
• Has had a fever for more than 24 hours
• Is lethargic, not eating, or vomiting alongside the fever
• Is a puppy under 6 months old with any elevated temperature
• Has a temperature above 41°C (106°F) — go to an emergency vet immediately
• Has recently been bitten by another animal
• Has been in a tick-endemic area and shows signs of illness

What NOT to Do When Your Dog Has a Fever

• Do NOT give human medications — Aspirin, ibuprofen (Advil), and acetaminophen (Tylenol) are toxic to dogs and can cause kidney failure, liver damage, or death
• Do NOT apply ice packs directly to skin — This can cause frostbite and shock the system too rapidly
• Do NOT try to force-feed — Offer fresh water and bland food, but don’t force it
• Do NOT wait too long — Fevers can escalate quickly in dogs, especially in puppies and senior dogs

If your vet isn’t immediately available and your dog’s fever is between 39.4°C–40°C, you can apply cool (not cold) water to the paw pads and ears as a temporary measure. Monitor closely and seek care as soon as possible.

Fever vs. Hyperthermia in Dogs

When trying to tell if your dog has a fever, it’s important to distinguish between true fever and hyperthermia. Not all elevated body temperatures are fevers. True fever (pyrexia) is caused by the immune system releasing pyrogens in response to infection or inflammation. Hyperthermia is an elevated temperature caused by external factors like heat or exercise — not immune response. Your vet will assess the cause to determine the right course of treatment. This distinction is key when trying to tell if your dog has a fever or overheating.

Frequently Asked Questions: How to Tell If Your Dog Has a Fever

If you are ever unsure how to tell if your dog has a fever, remember: when in doubt, check with a thermometer and call your vet. It’s always better to be cautious with a YMYL situation like your pet’s health.

The Bottom Line

Knowing how to tell if your dog has a fever is an essential skill for every dog owner. Every owner should be able to tell if your dog has a fever quickly using a thermometer and recognizing the 10 key symptoms above. Keep a digital rectal thermometer in your pet first aid kit, know the normal temperature range (38.3°C–39.2°C), and don’t hesitate to call your vet if something seems off. When in doubt, it’s always better to be seen than to wait — your dog depends on you to notice the signs they can’t communicate themselves.