Why Do Dogs Get Fevers?

4 min read

by Carol McCarthy

One of the challenges of being a pet parent is dealing with a sick animal. When you notice that your dog is moping around or turning up his nose at treats, he can’t tell you what is wrong. And unlike with a sick child, you can’t put your hand to his forehead to see if he has a fever.

In fact, a dog’s body temperature runs hotter than a human’s—from 99.5-102.5F—so if your dog does feel warm to the touch, that’s no surprise. You also can’t rely on whether your dog’s nose is cold and wet to indicate if he is healthy, says Dr. Susan O’Bell, a general practitioner at Angell Animal Medical Center in Boston.

“A warm or dry nose is a really unreliable indicator (of health), especially this time of year, when we are indoors where it is dry and warm.”

How Do You Know If Your Dog Has a Fever?

That determination is best left to your family vet, says Dr. O’Bell. Families often come in saying that their dog is not acting like himself, but the symptoms are too general to indicate a specific diagnosis.

“The most common thing I see is the dog is acting tired, is reluctant to get off his bed, or has a decreased appetite. Just like if you had the flu,” Dr. O’Bell says. 

One of the first things your vet will do is use a rectal thermometer­—which O’Bell calls the “gold standard”—to measure your dog’s body temperature. “That can be really tough to try at home,” she says with a laugh. Veterinarians sometimes use an ear thermometer, but she likes to verify that with a rectal reading.

A temperature of 104F or above is considered high, and your vet likely will order blood tests or other diagnostics to get to the cause of the fever. A temperature of 103-103.5F is less worrisome and might even be caused by your dog being excited or anxious while at the vet, Dr. O’Bell says.

Why Do Dogs Get Fevers?

The most common causes of fever in dogs are inflammation and infection. In New England, tick-borne diseases are the major causes of fever in dogs, Dr. O’Bell says. Tick borne diseases include Lyme disease, Rocky Mountain spotted fever (rickettsia), babesiosis, and tularemia, along with several others.

An infected wound also can cause a fever. Inflammation from auto-immune illnesses, such as those similar to Lupus, can cause fevers without infection. In fact, a study published in the Canadian Veterinary Journal in 2012 found that 48 percent of the 50 dogs studied had fevers caused by inflammation with no infection, confirming the predominance of non-infectious inflammatory diseases as causes of fever in dogs.

However, a fever accompanied by certain symptoms can be particularly worrisome, Dr. O’Bell says. Such symptoms include vomiting and other digestive distress, which can indicate that your dog has a virus, has eaten something harmful, or has a foreign body lodged in his stomach.


How Do You Treat a Dog With a Fever?

Once your vet determines the cause of the fever, he or she can begin treating him. Generally, the dog will need rest and fluids, assuming no serious underlying condition exist, says Dr. O’Bell. There are fever reducers that can be safely prescribed to dogs, however, your veterinarian will not prescribe anything until the cause of the fever has been determined. “We don’t recommend over-the-counter medicines or just giving them something at home,” Dr. O’Bell stresses.

It should be noted that you should never treat your dog with any kind of medicine without your veterinarian’s approval, as some conditions can be worsened with some types of medication.

It is also important to remember that a fever is a sign from your body that something is wrong and is not necessarily the problem itself.

“It might feel a little old school, but your body is trying to tell you something,” Dr. O’Bell says.

The best way to stay on top of your dog’s health before he gets seriously ill is to have a regular vet who knows your pet.

“We have all this information online, but it’s so helpful to have a relationship with a person who takes care of your pet,” Dr. O’Bell says.

Your vet will know what your dog looks and acts like when he is well and will know, for example, whether a slightly high body temperature is normal for him. “It’s good to get a baseline and to check it regularly,” Dr. O’Bell says.

If your dog does seem “off,” remember these simple dos and don’ts:

  • Don’t give your dog over-the-counter medicine without your veterinarian’s instructions.
  • Do call your vet to determine if a regular office visit or ER visit is indicated.
  • And don’t try to take your dog’s temperature rectally on your own!

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