basal body temperature charting BBT

Temperature charting can be a really useful process to help assess whether you are ovulating and to assess hormone balance right through your cycle.  When the egg is released from the follicle at ovulation the empty follicle that remains begins to produce progesterone.  It is the progesterone which makes the basal body temperature rise, and so charting shows us when ovulation has taken place and also whether ovulation is strong enough, and progesterone levels high enough, to support a pregnancy. 

how to start BBT charting

The idea is to take the temperature at its lowest point each day, this the basal temperature.  You need to have been asleep for at least 4 hours for the temperature to drop to its lowest level. You then take your temperature when you wake up before you do anything else.  The temperature naturally rises when we are active so you need to take it first thing.  If your sleep is disturbed for any reason, or if you wake at a different time than usual, then just make a note of it on the chart so we know to interpret that days result accordingly.

It is much easier to assess the hormone pattern when the temperatures are recorded on a graph rather than simply written down.  The main pattern that you are looking for is called a biphasic pattern - this simply means that temperatures are higher in the last 2 weeks of the cycle before the period comes.

You can download basal body temperature charts from and there are also a number of apps available for your phone.  However fertility apps have recently had bad press in terms of their accuracy in predicting ovulation, or when it is safe to have sex without conceiving.

Luteinising hormone (LH) ovulation predictor sticks and how to use them

Other information such as LH ovulation predictor test results, and cervical mucous changes can be added to the BBT chart.  Cervical mucous increases and becomes clear and stretchy like egg white when oestrogen levels are high.  Usually both LH and oestrogen levels peak the day before ovulation so the ovulation predictor tests can help us determine ovulation is imminent.  However a study which measured LH levels and monitored ovulation using daily ultrasound showed that the LH surge and not the peak LH levels are what we should look for.

research on LH testing

2015 study jointly carried out by SPD, who manufacture Clearblue, and University of Cologne showing that the LH ovulation surge is a reliable predictor of ovulation as measured by ultrasound, but the peak LH levels may not be until after ovulation