Take note that there are some factors that can affect your basal body temperature. It doesn’t mean that charting will be impossible, but it’s a good idea to mark these readings as questionable so your BBT chart will be easier to follow later.

Some things that may influence your BBT include:

• Being sick or having a fever

• Drinking alcohol the previous night

• Certain drugs or medications

• Stress

• Moving around before taking your BBT

• A broken thermometer or changing thermometers during your cycle

• Sleeping less than 5 hours during the night or not getting at least 3 consecutive hours of sleep before measuring

• Oversleeping

• Taking your BBT at a different time than usual

• Using electric blankets or heating pads when you don’t normally

• Change in room temperature

• Gynecological health issues

• Thyroid disorders

• Traveling to a new timezone or Daylight Savings Time

• Working night shifts

Any of the above factors can cause your BBT reading to be higher or lower than it normally would be. Just remember to make a note in your Glow daily log about these questionable readings.

As long as your abnormal temp is a one-off, you can treat it as an outlier. Basically, ignore it and let Glow draw a dotted line to connect the 2 temperatures on each side of it.

Again - if there’s ever any confusion as to what’s going on with your fertile window, you can always pay close attention to your cervical mucus or cervical position for signs of fertility as well.

Reference Source