Why does my reading fluctuate? Why do the temperatures change?

Two elements highly affect the temperature readings when taken: the first is method of reading and the second is location of reading.

Important to note: At a doctor's office, before a reading, nearly all of these concerns are solved by having you calmly wait for the nurse.
As such, please have the subject of the reading remain calm and be sitting for at least 20-30 minutes before reading for a more accurate temperature. Do not take the temperature after strenuous activity, after consuming hot/cold foods, or having been in direct sources of heat (like outside). The body will shift temperature to reflect the environment, so be aware that these will always affect your readings. (These variances can shift the temperature up to 2 degrees, so it is important that they be followed.)

METHOD: Please make sure to have the thermometer in place before taking a reading. If you are scanning the forehead, place the thermometer lightly between the eyebrows and then take the reading. If it is placed in the ear, please remove the probe cap, gently insert into the ear, then take the reading.

LOCATION: When using a forehead measurement, it is expected to be lower, anywhere from 0.5°F to 1°F lower as it is an external reading. Furthermore, forehead temperature reduces with age, the older an individual the lower the forehead temperature is expected to be. 
Therefore if it recommended to use these devices as a strong indicator of current temperature, learn your own normal reading that way you can identify if a result is outside of your normal temperature.

Nearly all MOBI thermometers have the ability to real an internal temperature via the ear. As with any thermometer, the closer to the source of the temperature, the more accurate the reading. Please remember that if your thermometer has the ability to do ear readings, that removing the probe cap and keeping the sensor clean by gently wiping with an alcohol wipe is highly recommended.