Learn how your temperature changes during your cycle and how you can use this information to detect ovulation.
Your basal body temperature is the lowest body temperature attained during rest, usually after sleep. Approximately one to two days after ovulation, a woman’s BBT will rise slightly and stay higher for at least 10 days. You can record your BBT to accurately detect if you ovulated and you can use this information to help predict future ovulations and I’ll be explaining exactly how you can do this.
The same hormones that control the phases of the menstrual cycle are responsible for raising BBT. Prior to ovulation during the follicular phase, higher levels or estrogen lowers BBT, then after ovulation during the luteal phase, higher levels of progesterone raise BBT.
Get yourself an accurate digital thermometer, one that can measure to the tenth of a degree. For example, it can measure to 98.4F instead of just 98F. There are different types of thermometers available, some may have a memory recall feature, or beep to indicate that the the reading is finished, but the most important thing to check is “can it measure to one tenth of a degree”? You are going to be taking you temperature everyday, so please ensure you know how to use your thermometer to get an accurate reading. Read the directions carefully. For example learn what the beeps mean or how long to leave it in if it does not beep.
Before we begin the steps, decide if you are going to log your temperatures into OvulationCalendar online via your phone or use one of our blank BBT charts below, click Celsius or Fahrenheit below to download.
Your BBT will rise slightly after you ovulate (see above sample), only by about 0.5 to 1 degrees Fahrenheit (about 0.3 to 0.5 degrees Celsius). Look for the temperature rise on your BBT chart. Your fertility reaches it’s peak two to three day BEFORE your temperature rise.
For example, if your average cycle length is 30 days and the number of days between your BBT rise and day before your next period was 11, you would add 2 to 11, to give you 13 (estimated ovulation day was 13 days before your next period). Then you would deduct 13 from 30 (your cycle length) which would give you 17. Your estimated day of ovulation is cycle day 17.
When you first start out monitoring your BBT it can be a little confusing. However, do not be concerned as it is typical for it to take a little while to get the hang of it never mind actually understanding what your temperature is telling you.
Despite your best intentions there are a number of factors that can affect your BBT and give you either a higher or lower than normal reading. These include:
– A late night
– Broken sleep
– Alcohol the night before
– Some pain relief medications
– Illness or fever
– Time zones
– Shift work
– Change of room temperature
Following our advice on how to get an accurate reading will really help you to understand your cycle and identify when you are most fertile. Inevitably, normal life will sometimes get in the way and it is very difficult to prevent factors like stress or illness for example, from interfering with your recordings. So, in addition to the steps above, see the following to improve the accuracy of your readings:
Taking your BBT is easy and gives you helpful information about your cycle and your fertility.
Dr. Tash, leading fertility expert explains how to accurately chart your basal body temperature (BBT) to identify ovulation to learn when you are fertile.