Use a basal body temperature thermometer
Take your temperature first thing in the morning
Measure before getting out of bed
Measure before eating, drinking, or talking
Measure at the same time each day
Use the same thermometer each time
Place the thermometer under your tongue or use the recommended method
Keep still while measuring
Record the temperature immediately
Track the temperature daily on a chart or app
Note any factors that may affect the reading, such as poor sleep, illness, alcohol, or travel