Reviewed by Amy Flowers, DVM on June 14, 2020
You may have heard that you can tell whether your dog has a fever by feeling their nose -- cool and wet is good, hot and dry means fever -- but it’s not true. In fact, dog fever often goes unrecognized or undetected. One reason it can be difficult to detect fevers in dogs is that their normal body temperature is naturally higher than in humans. The normal body temperature for dogs is between 101 and 102.5 F, compared to 97.6 to 99.6 F for humans. This means your dog may feel feverish to you even when their temperature is completely normal. The word “fever” is typically used to describe elevated body temperature caused by infection or inflammation. A temperature of more than 103 F is considered a dog fever, although it can be 103 if a dog is very excited or stressed. When dogs have high temperatures that are the result of hot external temperatures or excessive exercise in humid conditions, the condition is referred to as hyperthermia or heat stroke. When temperatures reach 106 F, serious and fatal complications can occur. Although there are no definite signs, some symptoms that might indicate illness and fever in dogs include: The only accurate way to tell if your dog has an increased body temperature is to take their rectal temperature. Experts recommend using a digital thermometer specifically designed for rectal use in dogs. Most thermometers intended for use in human ears do not work well for this purpose.
To take your dog’s temperature, first coat the thermometer with a lubricant such as petroleum gel or baby oil. Next, gently insert the thermometer about one inch into your dog’s anus and wait for results. Most thermometers sold for this purpose will take less than 60 seconds to register.
A variety of illnesses and conditions may make your dog run a fever. These include:
- Infection. This may have any number of causes, including bacterial, fungal, and viral diseases. Infection may be anywhere in the body, such as the lungs (pneumonia), the kidneys (pyelonephritis), the brain (encephalitis), or even the skin. The symptoms you see will depend on where the infection is focused and the underlying cause. Some infections, such as fungal diseases, can affect several areas of the body at the same time.
- Vaccination. A low-grade fever for 24 to 48 hours after vaccination is not uncommon and results from the interaction between the injection and the dog’s immune system.
- Toxins. Consuming substances that are poisonous to dogs, including macadamia nuts and some human antidepressants, can result in increased body temperature.
There are times when the cause of dog fever cannot be readily determined; this is called "fever of unknown origin," or FUO. The most likely causes for dog fever of unknown origin are disorders of the immune system, bone marrow problems, undiagnosed infections, and cancer.
If your dog has a temperature greater than 103 F, you should call your veterinarian. Fevers above 106 F are emergencies that must be treated promptly. If your dog has a temperature above 105 F, you can help bring their body temperature down by applying cool water to their fur, especially around the ears and feet. Using a fan on the damp fur will help lower the temperature. Be sure to monitor your dog’s rectal temperature as you do this, and stop the cooling procedure once it reaches 103 F. You don’t want to bring down the temperature too fast. If your dog has a fever, try to see that they drink small amounts of water on a regular basis to stay hydrated, but don’t force it. And never give your dog any human medicines intended to lower fever, such as acetaminophen or ibuprofen, as they can be poisonous to dogs and cause severe injury or death.
The average, normal temperature for dogs usually hangs around 101° Fahrenheit (38° Celsius), but it's normal for it to be one or two degrees higher or lower than this. These animals have ways to regulate body temperature on their own, especially panting, but they can become overheated or too cold due to the environment, infection or disease, age and size. Mild temperature elevations or dips are treatable at home in most cases, but high fevers and more extreme cases of hypothermia usually call for a trip to the vet. Pettable encourages talking with your vet if you notice any unusually high temperatures for your furry friends.
Regulation Mechanisms
Dogs have a number of internal processes and features that keep body temperature within the safe zone. The primary way they keep cool is to pant. When they do this, breathing quickens, which makes the heart work a little harder, and which forces air over the wet tongue and respiratory passages. Through the basic process of evaporation, heat is transferred from these structures to the air, and the cooler blood in those areas circulates to the rest of the body.
Although these animals do sweat, the only sweat glands they have are located on the pads of the feet, so these don’t do much in terms of keeping them cool. The hypothalamus in the brain is responsible for sending signals that control shivering, which creates heat as a byproduct as the muscles work, and the dilation of blood vessels in the skin, which allows heat to escape more easily as blood circulates. Additionally, their fur acts as a natural insulator, and they also have a condensed structure of arteries and veins, or rete mirabile, at the base of their neck that prevents much of the heat generated from the body from extending up into the brain.
Temperature Range
Although the average temperature for dogs is 101°F (38° C), it is normal to get readings as high as 102.5°F (39.2°C). The widely accepted bottom of the range is 99°F (37.2°C). Going outside of this range is a sign of sickness, or that the surrounding environment is much too cold or hot.
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Elevated Temperatures
Most veterinarians consider anything over 103°F (39.4°C) in a dog to be a fever. Much of the time, when temperatures are higher than this, it is a sign that the animal is fighting some kind of infection or other disease. They also commonly go up after a vaccination, however, because the immune system is busy trying to fight off the perceived threat. Eating or drinking certain things, such as macadamia nuts, also can cause elevation.
When a dog is too hot, its first reaction usually is to start panting. This involves the respiratory system, so it might also have a little trouble breathing and start coughing, often having some nasal discharge. It might become lethargic, depressed or not want to eat. Shivering can happen, as well, although it’s usually associated with being too cold, and some dogs become so overheated that they vomit, collapse or slip into seizures, coma or death.
If Your Dog Is Showing Signs of Anxiety
Your dog might experience some anxiety related to elevated or lower than normal temperatures. This depends on the dog and on whether or not they are uncomfortable due to some health related challenge they are experiencing. If your dog is presenting with signs of discomfort, anxiety, or is just generally uncomfortable it could help to give them something that helps calm them down until the underlying issue has been appropriately dealt with:
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Temperatures That Are Too Low
Dogs are considered hypothermic when their body temperature is less than 99°F (35°F), with moderate hypothermia ranging from 82 – 90°F (28 – 32°C) and severe hypothermia anything below 82°F (28°C). Occasionally, readings fall into these ranges because there is a problem with the hypothalamous, or because the pet has problems with its thyroid hormone levels. It also can happen simply because the animal is a puppy or a small breed, as both circumstances mean it is more prone to losing surface heat very quickly.
With mild hypothermia, a dog might shiver or have trouble concentrating and staying alert. Weakness also is common, and as the condition worsens, muscles can stiffen, blood pressure can go down and breathing becomes slower. In severe cases, it can be difficult to find a heartbeat. Fixed, dilated pupils may occur, as well as organ failure, coma and death.
How to Check Temperature
Pet owners have to take their dogs’ temperatures rectally, which is a fairly uncomplicated process. To do it, a person lubricates a digital or mercury thermometer with some petroleum jelly or other similar product designed for animals, and then inserts the thermometer slowly and gently into rectum. How far in to go depends on the size of the animal, but on most pets, at least an inch (2.54 centimeters) is necessary to get a good reading. After one or two minutes, or when the digital readout indicates the reading is done, the thermometer can be removed to check the temperature. In some cases, it can help to have another person help with the process, holding the dog still and keeping it calm, and experts recommend giving lots of praise or a tasty treat when done.
Adjustment and Treatment
An easy way to help regulate temperature is regular grooming. The amount and length of fur affects how much heat escapes from the skin, so routine combing and trimming often can keep the animal well. For small breeds, allowing a slightly longer coat or even adding a pet sweater can increase comfort. Larger breeds typically can handle a shorter cut and don't need additional layers.
Mild cases of fever and hypothermia often are treatable at home. If a dog is too warm, the first step is to bring it to a cooler location, after which it can be cooled with damp towels, a dip in a cool tub of water or a gentle spray with a hose or shower. Although it’s not good to force the animal to take in water, giving it the chance to drink something is essential, because it can’t cool through panting unless there is moisture on the tongue and respiratory structures that can evaporate. Extreme cases call for more invasive methods, such as giving cool fluids intravenously.
When mild hypothermia is the problem, bringing the dog where it is warmer and wrapping it in a few blankets is often all that’s necessary. In cases where getting wet is part of the cause for the temperature drop, some people even warm their pets using very low settings on hair dryers. If the temperature has fallen further, however, treatment might require more active rewarming, such as the use of a heating pad or warm bottles under a towel positioned under the torso. Intravenous treatment of warm fluids might be necessary.
Veterinarians generally recommend that pet owners bring their dogs in for professional care when fevers are above 103°F (39.4°C), or when rectal temperature has fallen below the mild hypothermia range. If a person isn’t sure whether to bring his animal in for treatment, it’s a good idea to call and ask. The vet generally can reassure a pet owner that he is on the right track with home treatments, and if necessary, he can provide basic instructions for how to transport the animal to a clinic without worsening symptoms.