The mean difference in temperatures between the initial temperature and the rectal temperature was 1.3 °F (P<0.001), with 25.9% of the patients having higher .
The most accurate way to measure temperature is to take a rectal reading. Fever. In most adults, a fever is an oral temperature above 100.4°F (38°C) or a rectal.
Here are step-by-step instructions on how to take rectal temperature in kids or adults who cannot hold an oral thermometer under the tongue.