8 How to Take and Record
your basal body temperature (BBT)
to accurately take and record your BBT
Learn how to identify factors
that may affect your BBT curve
Points in this Lesson:
The following guidelines
should be followed when charting BBT:
Take your temperature
at as close to the same time every morning as possible.
Take your temperature
as soon as you wake up, after a solid block of sleep, before moving
Use an accurate
thermometer (fertility/basal thermometer available at your
temperature as soon as possible after taking it.
You can take your
temperature orally or vaginally, but you must be consistent
throughout the cycle.
How to take and record your BBT
It is important to use
an accurate thermometer. Both digital and mercury thermometers are
effective, however, we recommend using a digital BBT thermometer. A
digital BBT thermometer gives a quick reading, beeps when it is
finished recording the temperature, and is easy to read. This can
make a difference when you are bleary-eyed first thing in the
morning. Your thermometer will likely store your reading for you, though we recommend to record it right away, either using the bedside notepad included in FertilityFriend.com's online app or using Fertility Friend Mobile App on your smartphone.
It is best if you can
establish a routine where you enter your data at the same time every
day just to form the habit so you will not forget. Missing data,
especially temperature data can skew the interpretation of your
chart. Once a routine is established, taking and recording your
temperature will probably start to feel as natural as brushing your
Some important guidelines to follow
when taking your BBT
temperature data will be most reliable if you follow these
guidelines. Not following these guidelines may make your chart
difficult to read and may make detecting ovulation more difficult as
note that these are ideal guidelines. We recognize that the realities
of your life may make meeting these ideals difficult or impossible at
times. Ovulation can usually be detected even under less than ideal
condition. The closer you can get to the ideal, however, the more
accurate and reliable your ovulation detection, analysis and
interpretation will be.
Take your temperature before rising in the morning as any
activity can raise your BBT.
Take your temperature at the same time every morning.
Take your temperature after at least three consecutive hours
Keep your thermometer accessible from your bed so you do not have to
get up to get it.
Use the same thermometer throughout your cycle if possible. If it
breaks or the battery dies and you use a new one, make a note of it
on your chart.
Keep a spare thermometer in case one breaks (especially if you are
using a glass thermometer).
If you use a mercury thermometer, shake it down the previous night
(or ask your partner to do it).
Temperatures can be taken orally or vaginally but it is important to
be consistent throughout the cycle since the temperature range may
vary. Most women prefer to take their temperatures orally, however,
when temperature patterns are unclear, switching to vaginal
temperature-taking for the next cycle sometimes makes the pattern
Record your temperature soon after you take it (or ask your partner
to) since most thermometers only store a reading until the next use.
If you have to do something else or want to stay in bed, you can
record it later, but we recommend recording it right away when
possible to avoid forgetting. You can use a bedside notepad in case
you are not able to enter your temperature on your chart right away.
If you must use a heating pad or electric blanket, keep it at the
same setting throughout your cycle. Make a note of its use.
Take your temperature before doing anything else including eating,
drinking or going to the bathroom. If circumstances arise that
prevent you from taking your temperature right away, take it as soon
as you are able and make a note of the circumstances.
If you have special circumstances on a temporary or an ongoing basis
and you are unable to follow all of the above guidelines, keep
temping anyway following the guidelines as closely as possible. Make
a note of your special circumstances in the notes section of your
chart. There is still a good chance that you will be able to chart
and see your fertility pattern.
Enter your temperature and always record the time you took it
on your data entry page. The time you took your temperature is also
important for the analysis.
The data entry field for Basal Body Temperature on
more details about data entry using FertilityFriend.com please [Click
entered your temperature data will be displayed on your chart:
that can influence your BBT
There are certain factors
that can influence your basal body temperature. These should be noted
on your chart. FertilityFriend.com's data entry page includes a
series of checkboxes and a custom data from to make this easy. These factors, should they
apply to you, will usually not make charting and chart analysis
impossible, especially if they occur only rarely, though it may be
more challenging. In most cases, even when these factors apply on an
ongoing basis, they will not skew your data so much that reading the
chart is impossible.
The following factors may
influence your BBT and should be noted in your chart data:
illness and infections (even those that do not produce a fever)
cold, sore throat
drugs and medications
alcohol (especially in large quantities, though all alcohol
consumption should be recorded)
smoking (if you smoke, you should consider quitting before you are