Which Thermometer Should I Use? Tips (and Science) for Measuring Your Pet's Temperature
In this article, Dr. Shadi Ireifej shares the science behind pet thermometry and practical recommendations for pet parents to measure their pet's temperature accurately.
By Pet Pro Supply Co. Featured Veterinarian,
Dr. Shadi Ireifej DVM DACVS
Chief Medical Officer at VetTriage
A pet's core body temperature gives tremendous insight into his or her current health status. Pet parents often want to be able to take their pet's temperature without going to the veterinarian, and this is quite easy with today's thermometers. They are safe, easy to use, accessible, accurate, digital, rapid, and consistent. Where pet parents still typically have questions is about where to place the thermometer to take the temperature. Also, just getting the temperature is not enough - it's important to also know how to interpret the different body temperature readings from each type of thermometer.
Common thermometer placement locations include oral, tympanic (“ear”), non-contact surface infrared (topical forehead and nasal skin regions), axillary ("armpit"), and rectal. The goal for all of these is to collect that numeric value which most closely resembles an individual's core body temperature, regardless of where on the body you measure, what device is used or what the patient's clinical status may be.
First we look at oral thermometry. Many people wonder why it's not typical to measure a pet's temperature orally, just like for humans. In fact, a human study comparing the different thermometer types in cancer patients in 2018 showed that it was oral thermometers that most closely represented true core body temperatures. However, in canine and feline patients, this is not the most viable option. The shape of their faces and the motor function of their jaws make the measurement less accurate, and there's also the risk of biting, breaking, or even ingesting the thermometer.
The same study established that tympanic ("ear") thermometry did not accurately represent core body temperature for humans. This modality can appear very practical (and non-invasive, compared to rectal thermometry!), but note that it can also be more difficult in some pets due to the wide variations in ear canal anatomy. However, some veterinarians and pet parents do prefer this option, especially for calmer pet patients that can tolerate it, who have rather shallow aural canals, who do not have aural disease, and for specific species to which rectal thermometry creates excessive avoidable stress. For such cases, the AMC PET-TEMP™ INSTANT ANIMAL EAR THERMOMETER by the Advanced Monitors Corporation is available.
What about measuring body temperature on the forehead? Unfortunately, this method is less reliable. A 2018 human pediatric study compared axillary and forehead thermometers. It determined that axillary measurements showed average values that were significantly higher than forehead measurements. Also, a veterinary study from 2017 determined that temperature measurements obtained using non-contact infrared thermometry (on the forehead and nasal regions of the head) was poor in consistency and agreement compared to rectal thermometry.
This leaves us with the rectal and axillary thermometer options. These were compared in a 2015 veterinary study. Mean rectal and axillary temperatures of dogs in that study were significantly different, with the rectal thermometry being higher than axillary. A similar study in 2014 concluded that although axillary and rectal temperatures were correlated in dogs and cats, there was a meaningful difference between rectal temperature and axillary temperature, suggesting that axillary temperature should not be used as a substitute for rectal temperature.
In plain terms: the most accurate core body temperature you can get is rectal. The veterinary profession considers rectal thermometry the most accurate and reliable method.
Unfortunately, rectal thermometry may just not be reasonable or safe in a home setting for pet owners. Even in a hospital setting, it can be difficult to use due to a pet's negative reaction to it or due to already existing anorectal disease in the pet. As such, axillary or even tympanic thermometry can be good alternatives, despite their shortcomings.
Unfortunately, rectal thermometry may just not be reasonable or safe in a home setting for pet owners. Even in a hospital setting, it can be difficult to use due to a pet's negative reaction to it or anorectal disease in the pet. As such, axillary or even in-ear thermometry can be a good alternative, despite their shortcomings.
For those unfamiliar with the axillary technique: simply tuck the thermometer tip deep into the armpit. When you get the measurement, add 1° to 2° Fahrenheit (°F) to the result. This will approximate the rectal temperature in the majority of cases. To give you a reference point, in the same 2014 veterinary study referenced above, it was determined that the median axillary temperature was 101.1°F in dogs and 101.2°F in cats. The median rectal temperature in that study for dogs was 102.0°F and 101.5°F for cats. So, that extra 1°F to 2°F is a great rule of thumb to use.
For pet parents that feel confident in their skills and who know that their pet would tolerate either rectal or axillary thermometry, the AMC RAPID DIGITAL RECTAL THERMOMETER - FLEXIBLE by the Advanced Monitors Corporation is a safe option. Because of its flexible tip, trauma or pain to the patient from inadvertent movement may be mitigated. This type of thermometer also has a much less likelihood of being damaged if inadvertent movement occurs by the pet.
For veterinary practice, however, the flexible thermometer may prove more frustrating because of its flimsier and more fragile build. As such, most hospitals utilize a rigid thermometer similar to the AMC RAPID DIGITAL RECTAL THERMOMETER - RIGID by the Advanced Monitors Corporation. We do not recommend everyone using this one at home, though, as it requires great skill to use without hurting your pet.
Pet owners are becoming more proactive about their pets' health, and at-home and telemedicine companies, such as VetTriage, are becoming more prevalent. With this shift, it may be suitable for doctors to discuss at-home thermometry with their clients. It is important to recall that body temperature values should be correlated with what is typical of the individual pet and the situation in which you are measuring the temperature. Remember: pet owners should always consult with a veterinarian before deciding that action should be taken after collecting any given body temperature! It can be dangerous, and even life-threatening, if action to cool or heat a pet is inappropriately taken.
1. Franconi I, La Cerra C, Marucci AR, Petrucci C, Lancia L. Digital Axillary and Non-Contact Infrared Thermometers for Children. Clin Nurs Res. 2018 Feb;27(2):180-190. doi: 10.1177/1054773816676538. Epub 2016 Nov 8. PMID: 28699399
2. Gates D, Horner V, Bradley L, Fogle Sheperd T, John O, Higgins M. Temperature Measurements: Comparison of Different Thermometer Types for Patients With Cancer. Clin J Oncol Nurs. 2018 Dec 1;22(6):611-617. doi: 10.1188/18.CJON.611-617. PMID: 30452002
3. Goic JB, Reineke EL, Drobatz KJ. Comparison of rectal and axillary temperatures in dogs and cats. J Am Vet Med Assoc. 2014 May 15;244(10):1170-5. doi: 10.2460/javma.244.10.1170. PMID: 24786164
4. Mathis JC, Campbell VL. Comparison of axillary and rectal temperatures for healthy Beagles in a temperature- and humidity-controlled environment. Am J Vet Res. 2015 Jul;76(7):632-6. doi: 10.2460/ajvr.76.7.632. PMID: 26111093
5. Omóbòwálé TO, Ogunro BN, Odigie EA, Otuh PI, Olugasa BO. A Comparison of Surface Infrared with Rectal Thermometry in Dogs. Niger J Physiol Sci. 2017 Dec 30;32(2):123-127. PMID: 29485631
About Dr. Shadi Ireifej:
Dr. Shadi Ireifej DVM DACVS is the Chief Medical Officer at VetTriage. He holds degrees from SUNY Binghamton and Cornell University and has practiced as a veterinary surgeon all across the United States. Follow him on Instagram @dr.shadi.ireifej and subscribe to his YouTube channel (Dr. Shadi Ireifej).
VetTriage is the world’s foremost provider of veterinary telehealth services. With VetTriage, pet owners have immediate access to triage advice from licensed veterinarians. Follow them on Instagram @vettriage and Facebook (facebook.com/televeterinarian).