How to Check a Dog for a Fever

Three Methods:Using a Rectal ThermometerUsing an Ear ThermometerReading The Thermometer and Assessing Your Next Course of Action

Unfortunately, your beloved canine companion cannot tell you in words when he or she is feeling ill. Instead, your dog can give you hints that it is not feeling well through changes in its behavior, including being less active or not as interested in food. However, finding out if your dog has a fever is a good way to figure out if it is actually sick. Documenting changes in body temperature could help a veterinarian to identify the cause of the illness in your dog and therefore help with treatment options. As part of your “doggy” first aid kit, you should have a dedicated doggy thermometer that you can use to find out if your dog has a fever.

Method 1
Using a Rectal Thermometer

  1. Image titled Check a Dog for a Fever Step 1
    Prepare the thermometer. Lubricate the tip with petroleum jelly or water based lubricant such as “KY jelly."[1] Lubricating the thermometer will make the experience slightly less uncomfortable for your dog.
    • If you have a digital thermometer, turn it on and make sure that it is in working order before inserting it into the rectum.
    • Most digital thermometers can read in Fahrenheit or Celsius. Check your thermometer’s directions to figure out how to change the type of reading.
    • Mercury thermometers should be shaken down to the end closest to the mercury tip before inserting to ensure the most accurate reading. The mercury thermometer may have both Fahrenheit and Celsius, you will have to check your particular instrument.
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    Have another individual restrain the dog's body. Have the other person give the dog a “hug” by placing his or her left arm under the neck of the dog and using his or her left hand to hold the side of the dog's face against the shoulder. Your helper will then place his or her right arm under the belly of the dog just in front of the back legs to keep the dog standing.
    • It is not uncommon for a dog to want to sit down when they feel a rectal thermometer inserted. If your dog is comfortable lying down and stays there for the temperature taking, then you can leave them lying down.
    • Sitting is not the preferred position because the rectum will not be easily accessible.[2]
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    Be cautious. If you have any indication that the dog may bite or you may injure the dog while trying to restrain your pet, stop! It is better to wait and take your dog to its veterinarian to get its temperature taken than to risk injury to the dog or yourself.
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    Lift the dog's tail to expose the rectum. Lift from the base of the tail, rather than the tip. This will give you more control over the animals movement and prevent the dog's tail from wagging.
    • It may be helpful to have your helper hold the dog's tail up for you.
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    Insert the thermometer into the dog's rectum about 1 inch (2.54 cm). Be careful not to insert the thermometer too deep, or too shallow, as this will affect the readings.[3] Try to gently insert along the side of the rectum, particularly if there is feces present.
    • The anus is the opening into the rectum, which is a long tube that collects feces. The anus is a muscular sphincter that relaxes and opens to allow feces to leave the rectum. The sphincter can shut very tightly if the dog is painful or afraid. Avoid forcing the thermometer through the anus, but do aim into the middle of the pucker where you will find the least resistance for your well-lubricated thermometer.
    • Remember to keep your hand steady and the thermometer straight.
    • Be deliberate in your approach.
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    Leave the thermometer inserted for the right amount of time. If you are using a digital thermometer, keep it in until it beeps. If you are using a mercury thermometer, leave in place for approximately two-minutes.[4]
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    Remove the thermometer gently. This has probably been a very intrusive and stressful experience for your dog, so be sure to use a soft touch. Clean the thermometer off after use - rubbing alcohol works well.[5]
    • Remember, this is the doggy thermometer for rectal use. It should not get mixed up with thermometers you use for humans.

Method 2
Using an Ear Thermometer

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    Lift the canine's ear and gently brush aside any hair that may be in the way. This will allow you to have a clear view of the animals ear canal. Any hair that remains in the way may obstruct the thermometer and cause discomfort to your dog.
    • Note that while ear thermometers are less invasive to the animal they can be less accurate if used improperly.[6]
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    Look for signs of an ear infection. If your dog has an ear infection, do not use the ear thermometer, as it will likely give you an inaccurate result and be painful to the dog. Indications of an ear infection are redness, swelling, discharge with an odor, and shaking or scratching excessively at the ears.[7]
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    Position the thermometer deep into the dog's horizontal ear canal. You may want to have another person hold the dog's head to get enough control of the animal to do this. Be sure the thermometer is deep enough or it will not produce an accurate temperature reading. [8].
    • If you don't have help, hold the dog's body between your legs to keep it still. At no time should you continue with this process if your dog is trying to bite you, as you will not get an accurate reading if the dog is fighting the process.
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    Hold the thermometer in place and wait for it to beep. This indicates a reading was successfully achieved. Depending on the brand and make of the thermometer, read times will vary.
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    Remove the thermometer from the dog's ear gently. Remember, ear thermometers go very deep into the horizontal ear canal. Some dogs may object to the ear thermometer, sometimes even more so than to the rectal option.

Method 3
Reading The Thermometer and Assessing Your Next Course of Action

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    Check the reading on the thermometer. A normal temperature should be between 100 and 102.5 degrees Fahrenheit (37.7 and 39.4 degrees Celsius).[9] Readings above 102.5 degrees Fahrenheit (39 degrees Celsius) are considered elevated.[10] Temperatures below 100 degrees Fahrenheit (38 degrees Celsius) are considered low.[11]
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    Double check any “abnormal” readings. If the temperature is too low, the thermometer may not be inserted far enough in the ear or the rectum, or it could be inserted into feces. If the temperature is too high and the dog is excited or really resisted handling, let the dog rest for 10 minutes and recheck.
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    Contact your veterinarian immediately if your dog's temperature is higher than 106 degrees Fahrenheit. This is very dangerous to your animal and should be considered a medical emergency.[12] If your veterinarian is not open or available, take your dog to the nearest emergency animal hospital.
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    Contact your veterinarian if your dog's temperature is above 103 degrees Fahrenheit. This is especially important if there are other indicators of illness, such as lethargy or lack of interest in food. Make an appointment to go in that day. [13]


  • If you are using a mercury thermometer, remember to shake it to reset. Glass mercury thermometers do add an element of danger should the glass break and/or release the mercury.
  • If you are using a digital thermometer, be sure that it is ready to read and does not need to be reset by shaking down the mercury toward the tip.
  • Be very cautious not to insert the thermometer too deep.
  • Take the dog's temperature in the ear and rectum if you are not confident with one reading. The results should be very similar if they are accurate.
  • Take your dog's temperature while it is healthy with no indication of any illness. This will provide a general baseline reading of your animal's normal temperature. Keep track of this and you will have numbers to compare to when your dog appears to be sick.


  • A canine temperature beyond 104 degrees Fahrenheit (40 degrees Celsius) or below 99 degrees Fahrenheit (37 degrees Celsius) indicates that a veterinarian should be contacted immediately.
  • Temperatures above 106 degrees Fahrenheit constitute a medical emergency for your animal.
  • Ear thermometers are faster at obtaining a reading, but are not accurate unless the proper technique is used.

Things You'll Need

  • Rectal or ear thermometer
  • Petroleum jelly or KY Jelly

Article Info

Categories: Canine Health