Dogs' temperature is measured through the rectum, which can be difficult to obtain in animals with aggressive nature, or those with ano-rectal conditions.  Alternative instruments and routes have also been developed. These alternative methods may yield different results. This study aimed to compare different methods in measuring the internal temperature of dogs.
Cases referred to the small animal clinic (n=20) for a general health check were included in this study upon confirming their health status. Axillary, tympanic membrane and rectal temperature were measured 30 minutes post-arrival.  Rectal temperature (RT) was measured first using a mercury thermometer and a digital thermometer.  Axillary temperature (AT) was measured using a digital thermometer.  The tympanic membrane temperature (TMT) was measured last using an infrared thermometer. Complete blood count (CBC) profiles, heart rates and respiratory rates of animals were within normal range. The difference between RT and AT ranged from 0.1°C to 1.1°C, whereas that between RT and TMT ranged from 0.03°C to 2.1°C. 40% of temperatures measured by AT and 90% of those measured with TMT differed by more than 0.5°C from those measured by RT. AT and TMT were positively correlated with RT (r = 0.833, P < 0.0001) and (r = 0.475, P = 0.035) respectively. AT and TMT were weakly correlated (r = 0.542, P = 0.014). The present study showed that RT shouldn't be substituted for AT or TMT in dogs. AT and TMT cannot be used interchangeably with rectal temperature in dogs.