Basal Body Temperature: How Does It Estimate My Ovulation?

by Aug 23, 2019

In the 1930s, women began tracking their basal body temperature to predict ovulation. This fertility awareness method is still commonly used for natural family planning to prevent pregnancy.

It’s not always easy to track your basal body temperature. Learning how to do it correctly is important for ovulation estimates. Read on for helpful tips and facts you should know about the BBT method.

What Is Basal Body Temperature?

Your basal body temperature (BBT) is your body’s temperature when you’re completely at rest. After you ovulate, your basal body temperature rises slightly.

Tracking these changes for several cycles may help women estimate their fertile window. Women use the BBT method in these ways:

  • To track ovulation while trying to conceive.
  • As a method of birth control.
  • As a way to detect infertility.
  • As a way to detect early pregnancy.

No matter why you use this method, you need to track your BBT every day. It requires tracking across several cycles unless it’s being used to detect pregnancy.

Basal Body Temperature And Ovulation

The rise in basal body temperature happens when your progesterone levels increase.

  • Basal body temperature is 97 to 97.5 degrees Fahrenheit before ovulation.
  • BBT increases to 97.6 to 98.6 degrees Fahrenheit on the days after ovulation.
  • The increase in temperature lasts several days and is called the luteal phase.

Your most fertile days are two to three days before your BBT rises. So, BBT can confirm your ovulation has occurred, but not predict when you will ovulate.

How To Track Your BBT To Estimate Ovulation

To use the basal body temperature method, yo`u’ll need to prepare ahead of time. There are tools to help monitor BBT.

Buy a basal body thermometer to take your temperature every day. BBT thermometers are slightly more accurate than regular thermometers.

Select a tracking tool to record your BBT. There are BBT chart tracking apps, and some women chart on graph paper. The picture below is an example of a BBT chart.

To track your basal body temperature, you’ll need to:

  • Take your temperature every morning. It should be taken at the same time each day.
  • Take your temperature before rising out of bed.
  • Use a BBT thermometer orally or vaginally. Use the same method every time.
  • Record your temperature using your basal body temperature chart.
  • Repeat the process for at least three cycles.

How Accurate Is The Basal Body Temperature Method?

The basal body temperature method is popular, but it can be faulty for several reasons. It doesn’t track a woman’s personal levels of luteinizing hormone. Without actually tracking your LH levels, you’ll only get an estimate.

Medical resources discuss the pros and cons of the BBT method and provide some statistics about them.

There are even more factors that can cause the BBT method to fail. For example:

  • You may not have time for consistent daily tracking.
  • Having a fever will make tracking inaccurate.
  • Being emotionally or physically stressed can raise your body temperature.
  • Consuming alcohol, drugs, and prescription medication can cause temperature changes.
  • Women do not always have consistent increases and decreases in BBT.
  • Women have unique menstrual cycles that may make charting difficult.

This information adds up and shows BBT tracking is not always reliable. Many risk factors that make it hard to estimate ovulation using the method. BBT is often not recommended by health care professionals as a reliable method to try to conceive or avoid pregnancy

Charting may help you find cycle patterns that you consider useful. Try an additional ovulation tracking method for more accuracy.

Other Ways To Track Your Cycle

There are other ovulation tracking methods you can use with and without BBT tracking. Below you’ll find widely used methods and a few details about them.

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Ovulation Calculators

Ovulation calculators and calendars are easy to use. You type the start date of your next period and your cycle length. This gives you an estimate of your fertile window. The calculator formula is simple, and you can even use it without the tool itself.

  • Formula – (day of your next period – 14 days = ovulation date) and (ovulation datefour days before date= fertile window)
  • Example – (September 22th – 14 days = September 7th) and (September 7th – four days before the 7th = (fertile window of September 3rd through September 7th)

Ovulation calculators are popular but flawed. The fixed formula doesn’t include factors like:

  • cycle length that varies each month
  • the unique ovulation patterns of every woman

This causes ovulation calculator apps and websites to have high rates of failure. For more reliable results, it’s best to combine these calendars and calculators with  another method.

Cervical Mucus Method

The cervical mucus method is often used with the BBT method . Your hormone levels rise during your fertile window, and your cervical mucus changes.

  • It may increase in quantity.
  • It is typically transparent in color.
  • It becomes thicker in consistency.

You’ll have to observe cervical mucus for many cycles to note patterns. Collect mucus by wearing a panty liner, wiping with toilet tissue, or finger insertion.

Many factors make it hard to rely on this method. These examples are common:

  • sexual intercourse can cause mucus changes
  • infections can also cause mucus changes
  • mucus consistency changes when it dries on panty liners

Only 23 out of 100 women get pregnant during their first year using this method. You may not want to rely for conceiving quickly.

Ovulation Test Kits (OPK)

Ovulation test kits are the most accurate tracking method. They are 99% accurate because they measure luteinizing hormone levels. LH surges happen during your fertile window, so you’ll know the best days for conception.

Many ovulation test kits show positive results when your LH level meet a minimum threshold. This causes false negatives if your own LH levels are lower than the minimum.

For personalized feedback, the Mira fertility tracking kit is an excellent choice. Mira shows you your exact LH concentration for highly accurate results. It also syncs with an app to provide AI-powered information about your cycle, automatic charting, and more.

Order Your Mira Today

Ready to easily, precisely, and automatically track your ovulation cycles? Let Mira take the guesswork out of getting pregnant, so you know exactly when to conceive.

Reserve Your Mira Today

Ready to easily, precisely, and automatically track your ovulation cycles? Let Mira take the guesswork out of getting pregnant, so you know exactly when to conceive.