Fever in dogs is a difficult clinical sign to monitor, unlike in humans, where it is one of the first measurements taken and one of the first signs of disease. Unlike in humans, fevers in dogs are difficult to measure. It often stresses the dog out to get their temperature taken, let alone the humans who have to watch and sympathize! As a result, most dogs only have their temperature taken at the vet. And even then, it might only be when absolutely necessary.
Read to learn more about fever and why humans usually don’t know if a dog has a fever, especially without taking a rectal temperature.
What Is Fever?
A temperature over 102.8°F, or 39.3°C, is considered abnormal. However, since many dogs are also stressed when taking their temperature, which can raise their body temperature without a fever, most of the time, a temperature up to 103°F is not too worrisome, but anything over 104°F is.
The higher the temperature of the fever, the more dangerous and deadly it becomes. The normal body temperature for a dog is 100.2–102.8°F (37.8–39.3°C).
The hypothalamus, a part of the brain, monitors body temperature, changing different bodily functions to heat up or cool off a dog’s body as needed. For example, if the dog gets hot, the hypothalamus sends signals to begin panting. In a fever, the hypothalamus temperature is reset higher than normal.
During a fever, the metabolism of the body increases, creating a greater need for fluid and calories. This is why prolonged fevers often result in weight loss, and dehydration can happen so quickly. In certain conditions, the body temperature can rise above the hypothalamus set point despite its best efforts to cool off.
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What Are the Signs of Fever?
This is the important and confusing part of the article. Unfortunately, without sticking a thermometer up their bum, there is no way to know for sure if a dog has a fever. They may have some of the following signs of a fever:
Lethargy
Inappetence
Fast heartbeat
Slow breathing
Bright red gums
Dehydration
Hypovolemic shock
But these signs are very vague, and many other health problems can also cause them. As a result, it is difficult to know if a dog has a fever, so it is not a reliable or sensitive tool for monitoring the health of most people.
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What Are the Causes of Fever?
The pyrogens that cause fever can be internally or externally derived. Usually, if they are internal, it results from inflammation or an out-of-control immune system. External pyrogens are infectious agents or other toxic substances. Here is a small list of examples:
Infectious diseases:
Parvo
Distemper
Leptospirosis
Lyme disease
Anaplasmosis
Medication reactions:
Vaccines
Tetracyclines
Penicillin’s
Vaccines
Inflammation:
Pancreatitis
Cholangiohepatitis
Meningitis
Rheumatoid arthritis
Immune-mediated hemolytic anemia
Hypersensitivity reactions:
Allergic reactions
Inflammatory bowel disease
Cancer:
Lymphoma
Mast cell tumors
Metastatic neoplasia
Image By: Lindsay Helms, Shutterstock
How Do I Care for a Dog With Fever?
The first thing to do with a dog with a fever is figure out why they have it. Without a proper diagnosis, treating a fever is not only difficult but dangerous if the wrong thing is being treated.
Unfortunately, there is no magic pill that fixes all the different types of fevers listed.
A vet can help manage and try to reduce the fever with emergency critical care at the hospital. But without knowing the primary cause, the fever will remain unresolved.
Identifying the cause of the fever may be involved. It will likely require veterinary testing, including (but not limited) to the following:
Physical exam
Blood work/testing
Urine analysis
Diagnostic imaging (X-rays or ultrasound)
Advanced imaging (MRI or CT)
Frequently Asked Questions (FAQs)
What is the difference between hyperthermia and fever?
Hyperthermia, fever, and pyrexia all these terms may all be used interchangeably. So, for example, you may see in your vet notes the same condition described in all three terms. While technically, they all mean slightly different things in terms of practicality, they all mean an elevated body temperature.
In hyperthermia, the body has become too hot, bypassing the hypothalamus set point. This is what happens in heat stress, for example. It can also occur in other conditions, such as seizures.
Trying to guess if your dog has a fever is not worth it. Other clinical signs of health problems are much more sensitive and specific than a wild guess about body temperature.
It is much more effective and a more specific indicator of disease to watch for the observable changes that may or may not indicate a fever but indicate something is not quite right. Look out for these signs:
Lethargy
Depression
Inappetence
Why is my dog’s nose dry and hot?
The home-spun myth that a dry nose is a sign of fever in dogs is wrong. Dogs can have a dry nose for all sorts of reasons, the biggest one being it is normal for them and their breed to have a dry nose.
My dogs’ ears are hot. Do they have a fever?
Many people worry about their dogs’ ears being hot as a sign of fever. However, the number one reason a dog’s ears get hot and red is because of an ear infection, not a fever.
Hot ears need to be investigated by a vet, but they are rarely a sign of fever.
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Will my dog get a fever after their vaccines?
Vaccines can have side effects. But trying to decide if your dog has a fever or not is difficult at home. It is more realistic and practical to monitor things that you can observe, such as:
Soreness at the injection sight
Lethargy
Inappetence
Vomiting
Diarrhea
Hives
Anaphylactic shock (swelling around the face and/or eyes)
Collapse
If you observe any of the last few signs of severe vaccine hypersensitivity reactions, bring your dog to the emergency vet right away. And report your observations in terms that you and the vet can measure together.
What can I give my dog if they have a fever?
A trip to the vet is the best option. Medicating them is probably not the best idea without a veterinarian’s specific advice.
Not only is it tough to know if a dog has a fever for real, but so is giving them medication to treat a thing they may or may not have been dangerous.
But if your dog does indeed have a fever, it is probably not an insignificant problem. Treating the fever and reducing the body temp alone will not help them in the long term. And in fact, it may further endanger your dog by prolonging diagnoses and obscuring key clinical signs.
Keep them cool and comfortable while bringing them to the vet.
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Conclusion
Fever in dogs is a tough clinical sign. It can be frustrating that it is not easier to monitor and is so different from human medicine. But monitoring your dog’s health in terms of identifiable and easy-to-measure symptoms is much more sensitive and specific.
A dog with a fever confirmed at the vet will need all the TLC and veterinary medicine they can get. Fevers are taken seriously once they are confirmed, and monitoring them is a group effort.
Dr. Chantal is passionate about the human-animal bond and improving animals' lives through their connections with their human companions. She has worked with many different species, big and small, including dogs, cats, birds, rabbits, guinea pigs, reptiles, amphibians, and even horses and mice. Chantal is excited to share her knowledge using her writing to help people connect with their animal friends.
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