Luteal Phase 101 - The Basics

What is the luteal phase?

A luteal phase is one of the three phases of the menstrual cycle that is necessary for reproduction. This is the phase that occurs after ovulation and continues until the day before a woman’s next period. This phase ordinarily lasts about two weeks (14 days) and is often used with an Ovulation Calendar to calculate the time of ovulation. The luteal phase may vary among women, but the length is usually relatively the same for the same woman. 

The importance of the luteal phase

The purpose of the luteal phase is to produce progesterone that prepares a woman’s body for pregnancy. The length of this phase is usually constant and can be used to establish the time of ovulation with the woman’s menstrual cycle. This is important in planning or avoiding pregnancy. An Ovulation Calendar such as the “My Calendar” used by some women can use the length of the luteal phase and the number of days in the menstrual cycle to determine when ovulation will occur. A simple example is seen with a 28-day cycle and a luteal phase that is twelve days long. According to this information, ovulation should take place on day sixteen of the cycle. The calculation used to determine this date is the days of the luteal phase (12) subtracted from the days of the cycle (28).

How Does a Woman Determine The Length Of Her Luteal Phase?

The average length of the luteal phase for most women is fourteen days. Another way to find the length of a luteal phase can be determined by charting the Basal Body Temperature (BBT), which is known as the waking body temperature. The BBT rises after ovulation. Count the number of days from the rise in the BBT until the menstrual period, will provide the length of a specific woman’s luteal phase. Using the steps below, BBT can be charted to determine a woman’s personal luteal phase:

  1. Take your temperature first thing every morning. Temperature should be taken before any activity in order to get the most accurate reading.
  2. Every effort should be made to take the temperature at about the same time every morning. The point is to get the temperature under the same conditions every day. It is advised to note the time taken each day to explain any discrepancies in the final results
  3. Record the temperature on a chart. You could use “My Calendar” or make a BBT chart specifically for this purpose.
  4. In addition to the time of day, other uncommon activities should be noted such as travel, moving, illness, any type of stress can affect the temperature pattern. 
  5. Take a pen and connect the temperatures on the chart to note the range.
  6. The point where the temperature shifts and stays at a higher range than the previous temperatures, this marks the beginning of the luteal phase and ovulation has happened. The key to note is that after ovulation temperature are higher than the prior range of low temperatures.
  7. The luteal phase ends when the menstrual period begins. Temperatures tend to drop back down to the previous low numbers.

The length of the luteal phase is the period of time that begins on the day ovulation occurs, and ends on the day before the menstrual period begins. As previously noted, this tends to be about fourteen days.

Can a Woman Know The Length Of Her Luteal Phase Without Doing the Chart Activities Above?

Any luteal phase can be determined by charting the waking temperature every day for a month, as spelled out above. However, if a woman just needs an estimate, she can use the average of fourteen days, which is the length of the luteal phase for most women. Using the acceptable average will give a good approximation on an Ovulation Calendar for the time a woman will be generally the most fertile.

Read also:

Ovulation Basics
Ovulation and Pregnancy
Ovulation and Contraception
Irregular Menstrual Cycle
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