BBT Charts for Ovulation Tracking [MUST READ]

Trying to get pregnant can require a lot of work. You’re only fertile for a short period of time each month. Finding ways to determine when this fertile window occurs is often one of the biggest challenges of fertility.

Luckily, there are several methods for tracking ovulation and identifying the best time of the month for fertilization. One of the most commonly recommended methods is to check your cervical mucus. However, tracking your basal body temperature (BBT) is also a great resource for monitoring your cycle.

Here is everything that you need to know about BBT charts and using the information that you gather to determine your fertile window.

What Are the BBT Charts?

Basically, a BBT chart allows you to track ovulation. A BBT chart is a simple way to monitor changes in your basal body temperature (BBT) throughout your menstrual cycle.

Your BBT is the temperature of your body when it’s at rest and is typically slightly lower than your normal body temperature. As your BBT trends to rise slightly just after you ovulate, tracking this temperature each day throughout your cycle may help provide useful information about your fertility.

When combined with other natural family planning methods, such as checking your cervical mucus, you may naturally determine the best days of the month for trying to conceive.

The typical recommendation is to use a thermometer that can provide a reading that is accurate to 1/100th of a degree, while most thermometers provide a reading that is accurate to 1/10th of a degree. For example, a specialized BBT thermometer may give you a reading of 98.61, while a standard thermometer simply displays 98.6.

You may not need the extra decimal place to accurately track your BBT. However, the extra accuracy can help detect smaller changes in your BBT.

When checking your temperature, it’s best to check it first thing the morning before you even get out of bed. You also need to perform this task each day and keep track of the results, either in a notebook or using a BBT charting app on your phone.

The Ava app, for example, does a good job at storing and analyzing your data.

How Does BBT Vary During Your Menstrual Cycle?

How can your BBT help track ovulation? Throughout your menstrual cycle, your BBT should change slightly. It tends to be slightly higher right after ovulation and slightly lower just before ovulation.

Tracking these changes gives you two pieces of data to help determine when you’re most likely to ovulate during each cycle.

Most women have a biphasic pattern to their BBT. This means that their cycle has two phases – the follicular phase and the luteal phase.

The follicular phase begins on the first day of your menstrual period and it ends when ovulation occurs. During the follicular phase, your BBT should be lower than normal. For example, your BBT may fall into the 97.0 to 97.6 range.

After ovulation occurs, the luteal phase begins. During this phase, your body begins to produce a hormone called progesterone. Progesterone is often called the pregnancy hormone, as it is an important part of pregnancy and fertilization.

Progesterone prepares the uterus for accepting a fertilized egg. Increases in this hormone help prevent muscles contractions that may result in the uterus rejecting the egg. It also helps to create a hospitable environment for the baby.

Besides helping prepare the uterus, this hormone also causes a slight increase in your BBT. During the luteal phase, you may notice temperatures ranging between 97.7 and 98.3. This phase continues until you have your period and the cycle repeats itself.

Five Main Types of BBT Charts

When you track your BBT, a pattern should begin to develop. You can use this pattern to predict when you’re going to ovulate each month. However, you may need to track several cycles before you get a clear indication of the changes in your BBT.

As your temperature increases starting on the day of ovulation, you can use the increases in BBT to track when ovulation occurs. You can also use the lower body temperatures to estimate the opening of your fertile window, which typically starts four or five days before ovulation.

The pattern that emerges is often referred to as a pattern, curve, or shift, depending on how the data appears when charted.

There are five main types of BBT charts that you may detect while tracking your temperature.

1. Normal or Biphasic Pattern

Normal Biphasic BBT Charts for Ovulation Tracking

Most women have a biphasic pattern. As mentioned, this means that you have two separate phases. This normal pattern consists of a small drop in BBT before ovulation and a small rise in temperature immediately after ovulation due to the increase in progesterone.

2. Triphasic Curve

Triphasic BBT Charts for Ovulation Tracking

A triphasic curve occurs when you detect three separate rises in your BBT during your cycle. You may still see a small drop in BBT before ovulation, followed by a normal rise after ovulation. However, the triphasic curve includes another rise about seven to ten days after ovulation.

In some cases, this third rise in body temperature may be a sign of early pregnancy. After fertilization, your body continues to produce additional progesterone.

The placenta also begins to produce this hormone. These changes can cause a small increase in your BBT, possibly indicating early pregnancy.

3. Anovulatory or No Thermal Shift

Anovulatory BBT Charts for Ovulation Tracking

An anovulatory BBT chart indicates that your menstrual cycle didn’t include ovulation. Anovulation is the lack of ovulation and may be the result of stress, low body fat, and other health issues.

Along with no thermal shift, you may notice that your cervical mucus remains sticky and creamy, instead of becoming more like egg whites.

When you detect no thermal shift in your BBT throughout your cycle, you should consult with your gynecologist to determine the possible cause.

4. Ambiguous Thermal Shift

Ambiguous BBT Charts for Ovulation Tracking

An ambiguous thermal shift refers to a BBT chart that is difficult to read. The results are ambiguous, providing no real insight into whether you’re ovulating or when you’re ovulating.

For example, you may notice several short rises, erratic patterns, or incredibly small changes in your BBT throughout your cycle.

When you get an ambiguous BBT chart, you should continue to track your BBT each cycle. The ambiguous chart may simply be a one-time issue. However, if you continue to have trouble discerning any noticeable rises in your BBT, a doctor visit may be necessary.

5. Slow-Rise or Monophasic Pattern

Slow Rise BBT Charts for Ovulation Tracking

A slow-rise is another type of BBT chart that you may see. This is also called a monophasic pattern, as it only includes a single gradual rise in body temperature throughout the menstrual cycle.

A slow-rise doesn’t necessarily reduce your chances of getting pregnant. These charts may occur if it takes your body a little longer to produce more progesterone.

While a monophasic pattern may not be a sign of any fertility issues, it can make it more difficult to track ovulation.

Is a Triphasic BBT Chart a Sign of Early Pregnancy?

The triphasic BBT chart is the chart that most women hope to see, as it may indicate early pregnancy. When the sperm successfully fertilizes an egg, your body continues to produce progesterone, instead of slowly decreasing production.

In fact, the placenta also produces progesterone, leading to an extra spike that may cause a third rise in your BBT around the same time that the hCG pregnancy hormone begins to increase.

However, a triphasic BBT chart doesn’t guarantee pregnancy.

What are the Possible Causes of a Triphasic Pattern?

Besides pregnancy, there are other possible causes of a triphasic pattern. One of the most common reasons is a change in the temperature of your bedroom.

When tracking your BBT, you should check your temperature before getting out of bed and try to check at the same time each day, as any small change can impact your body temperature.

If your bedroom is a couple degrees warmer, either due to warmer weather or setting your thermostat higher, you may notice the third rise in your BBT chart.

Another possible cause of a triphasic pattern is a second spike in progesterone levels during your luteal phase. This may simply be a hormonal imbalance or a false pregnancy.

Should You Take an Early Pregnancy Test for a Triphasic Pattern?

While a triphasic pattern may indicate early pregnancy, most doctors advise against taking an early pregnancy test. Pregnancy tests detect the hCG hormone, which begins to rapidly increase after fertilization.

However, it can take up to two weeks after fertilization for the hCG levels to get high enough for detection. Taking the pregnancy test early may also increase the risk of a false negative.

Should You Worry If You Don’t Have a Normal Pattern?

If you track your BBT and detect an anovulatory chart, ambiguous chart, or a slow-rise, you may be worried about your chances of getting pregnant.

If you don’t have a normal pattern, your BBT chart may be caused by factors other than fertility issues, as hormonal imbalances, stress, and warmer weather can all impact your chart.

You shouldn’t worry about something that you can’t fully understand. Without additional information, it can be difficult to determine what these charts indicate.

Instead of allowing a chart that is not normal to cause stress, you should schedule a visit to your doctor’s office or a fertility specialist.

Last Thoughts on Tracking Ovulation with BBT Charts

Tracking your basal body temperature (BBT) is the only natural method for accurately determining when ovulation has occurred. When you combine BBT charting with checking your cervical mucus, you can gain a more accurate indication as to when you’re going to ovulate each month.

Keep in mind that you may experience slight changes that make it difficult to determine when ovulation occurs. You need to continue to track your BBT and mucus each cycle and compare the results each month to begin painting a clearer picture of your typical fertile window.

If you want a natural way to track ovulation and increase your chances of getting pregnant, start charting your BBT.


I’m Princila, founder of Check Ovulation and a proud mom of two. I’m an alumna of James Lind Institute. After working in clinical jobs, my passion for writing took its toll, and I ended up switching careers to work in the medical publishing industry. I also have a passion for healthy food, which prompted me to take several online courses in nutrition and health offered by Wageningen University. (I still haven’t completed the courses thanks to my busy mommy schedule!). When I’m not writing/editing scientific and medical manuscripts or taking care of my family, I use my free time to research, learn, and write about healthy living. I have also authored a few books in the self-help niche using the pen names Princila Murrell or PN Murray. Protection Status