Are you curious about how long it takes for basal body temperature (BBT) to rise after ovulation? The answer is that BBT typically rises approximately 24 hours after ovulation has occurred. But here’s the thing: there are several factors that can create higher temperatures, making it crucial to understand how BBT works in conjunction with other methods for tracking ovulation.
As a mom who used BBT tracking to aid in getting pregnant with my littles, I’m here to share my insights and experiences. I also credit BBT tracking in conjunction with other methods that I will mention in this article with helping me to get pregnant on the first try.
However, it’s important to note that while I’m passionate about this topic, I’m not a doctor or medical professional. So, before embarking on your own fertility journey, be sure to consult with a health care provider or reproductive endocrinologist who can provide you with personalized advice.
This article is meant for mamas and mamas-to-be who want to use BBT to track ovulation and their fertile period, who are trying to get pregnant.
This post contains affiliate links. If you purchase something through one of these links I may earn a small commission. As an Amazon Associate, I earn from qualifying purchases. Thank you for the support!
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What is BBT?
BBT Stands for Basal Body Temperature. It is the temperature of your body when you’re completely at rest. Basal body temperature is sometimes called your rest temperature or morning body temperature.
BBT is usually measured first thing in the morning before any movement or activity. You should take your BBT at the same time each day before getting out of bed and record your temperature (more on that later).
Basal body temperature for most women will be between 96 and 98 degrees before ovulation. BBT usually rises 0.5 to 1 degree after ovulation. This is known as the thermal shift.
A sustained 3-day temperature indicates ovulation occurred 24 hours before the first temperature spike (see diagram below).
It is important to note that basal temperature cannot predict if or when you are going to ovulate. Basal body temperature will just confirm the day of ovulation. Since it will take a sustained BBT rise of 3 days, you won’t know whether you ovulated until 3 days after using the BBT method.
Your fertile days are the 5 days leading up to ovulation and the day of ovulation. Meaning you will be most fertile 6-9 days before you confirm ovulation using BBT.
This makes BBT alone very tricky as a fertility awareness method, and not reliable as a form of birth control.
That being said tracking your BBT along with other methods of tracking your menstrual cycle can be very effective for those trying to determine their fertile window while trying to conceive (TTC). Here’s how:
The Menstrual Cycle
When I first started TTC, I was completely clueless about my menstrual cycle 🤔. I had no idea about follicles, luteinizing hormone, the corpus luteum, cervical mucus, the luteal phase, progesterone, or any other aspect of my period.
It took a lot of research to understand my cycle, and then even more learning when I started tracking it on my own.
Let me break down the menstrual cycle as easily as possible. I’ve also included cycle days for each phase, but please note this is for a “normal” 28-day cycle. By tracking your cycle you will start to understand how long your personal cycle is and how long each phase is.
There are three phases in the menstrual cycle:
- Follicular Phase (Day 1-13): The follicular phase occurs at the beginning of the cycle. Several ovary follicles begin to develop and mature under the influence of estrogen. Follicles are small sacks of fluid that carry eggs inside of them. Eventually, one dominant follicle emerges, leading up to ovulation.
- Ovulation (Day 14): Ovulation is the second phase where the mature egg is released from the follicle from within the ovary into the fallopian tube, making it available for fertilization. This phase is characterized by a surge in luteinizing hormone (LH) levels. The egg is only viable to be fertilized for 12-24 hours after it is released.
- Luteal Phase (Day 15-28): Once the egg is released, the luteal phase begins and basal body temperature rises. The follicle hangs back in the ovary and transforms into what is called the corpus luteum. The corpus luteum releases the hormone progesterone, which prepares the uterus and uterine lining for pregnancy.
Using BBT to Determine Ovulation
If you are TTC, knowing exactly when you are ovulating is the most important piece of the puzzle. Remember, you want to time intercourse during the most fertile days of the month which are the 5 days leading up to ovulation and ovulation day itself.
Since your eggs are only viable for 12-24 hours after you ovulate, the chances of getting pregnant more than 24 hours after ovulation is virtually zero.
Importance of charting
You might have heard of BBT charting. Temperature charting is essential to keep track of your cycle. You want to track your BBT every day.
There are several apps that I used. For BBT tracking I really liked Fertility Friend. You get a nice visual chart that is easy to read. It also marks when you likely ovulated once it confirms the temperature rise.
Maintaining a BBT chart helps identify patterns and changes so that you can better predict ovulation day.
Remember your fertile window is the five days leading up to ovulation and ovulation day (6 days total). Let’s say you track your cycle for 6 cycles and notice that you always ovulate on cycle day 13 or 14. Your fertile window will be days 8-13 or 9-14. You should have sex as often as possible on cycle days 8-14 to have the best chance of getting pregnant.
Tracking other signs: Cervical mucus, ovulation predictor kits, and their correlation to BBT
Fertility apps like Fertility Friend and Premom can also help you track your cervical mucus, cervical position, ovulation predictor kits (ovulation tests or OPKs), and pregnancy tests. The more information you have for your chart, the more accurately you can predict ovulation before it happens, and confirm it when your BBT rises.
BBT rise: How long after ovulation does BBT rise?
The exact timing of BBT rising after ovulation isn’t a clear-cut answer. BBT has to be taken at the same time each day to be accurate. The rise in temperature is only significant after 3 consecutive days. You can ovulate at any time of day, and unless you experience Mittelschmerz (ovulation cramps), you likely aren’t going to ever know the egg’s release down to the hour or minute.
What you do know is that after the sustained temperature rise for 3 or more days, you can confirm that you ovulated in the 24 hours prior to the first day of the thermal shift.
Taking Your BBT
In order to get the most accurate reading, here are a few tips that I used.
Tools and techniques
Take your basal body temperature at the same time each day (even on the weekends). This can be tricky depending on your work schedule or lifestyle.
Set an alarm on your phone and stick to taking it every day. Some thermometers have built-in memory, so you don’t have to wake up and chart your temperature at that time, you just have to wake up enough to get the reading.
Take your BBT laying down in bed, before moving. Small movement just to reach for the thermometer is ok. Have your thermometer on your bedside table.
Take your BBT after 3 or more hours of uninterrupted sleep. If you’ve woken up to go pee in the night, tended to a child, or breastfed, those can all affect your reading.
You need a special thermometer to track BBT.
You shouldn’t use a regular digital thermometer that only measures to the tenths of a degree. Those thermometers are often called “fever thermometers.”
Because the change in temperature can be so subtle (half a degree or even less), you need a digital BBT thermometer that takes temperature readings to the hundreds.
Pro Tip: A one-tenth-of-a-degree temperature reading from a regular thermometer looks like this: 96.8 (one decimal place) whereas a one-hundredth-of-a-degree temperature reading looks like this: 96.82 (two decimal places).
A special basal thermometer is key to tracking the slight rise in temperature. There are so many digital BBT thermometers on the market. Some are integrated with an app and track your temperature for you. Others have features like backlights, built-in memory, and quick read-time.
- Backlight: backlighting on a BBT thermometer is more helpful than you would think, especially if you are temping in the early hours of the morning. You can easily see your temperature reading without having to turn on a light or your phone light.
- Built-in memory: I always thought I would remember my BBT to be able to add it to my basal body temperature chart after I woke up… And I rarely did. Having a thermometer with a “last reading” memory saved me on many occasions where I forgot the exact temp by the time I woke up. Some thermometers can store 30 days or more worth of data.
- Read Time: regular thermometers give readings in as few as 10 seconds, but basal body thermometers take up to 5 minutes to read. I can speak from experience when I say, the quicker the read time, the better. Especially at 6:00 AM on Sunday when you are not ready to be awake.
- Wearable device: There are some wearable devices now for monitoring fertility. Although there are several products marketed for this on Amazon, the only wearable BBT product that I am aware of is the Avia Bracelet.
Mom-to-Mom: You don’t have to have a fancy basal thermometer to be able to accurately chart your BBT. You can find a regular basal thermometer in the pharmacy section of most grocery stores. The MABIS thermometer that I chose was because it was even cheaper than the pharmacy’s in-store prices. Don’t think that more expensive means better, they usually just have more features.
Again, I love Fertility Friend. I also found it very useful to join the TTC group on Baby Center, which is a forum for moms and moms-to-be who are trying to get pregnant.
The women on there are extremely used to reading fertility charts and Fertility Friend makes it really simple to download your chart and share it.
You can also manually track your menstrual cycle on a paper chart, or use your BBT with OPKs and apps like Premom.
Just remember that even if you see a temperature spike, that doesn’t mean you’ve ovulated. The temperature rise needs to last at least 3 days before you can determine that you ovulated.
BBT Accuracy Considerations
The biggest hurdles to getting accurate results with BBT are just human error and external factors. Basal body temperature is the lowest body temperature of the day. Many other factors might cause temperature changes like sleep interruptions, traveling and jet lag, taking your temperature at different times, and getting sick. If you have a fever you won’t be able to use the basal body temperature method until it goes down.
Interpreting BBT Chart and Detecting Ovulation
Identifying Ovulation Day
Contrary to what many believe, ovulation day is not the day that BBT rises. Ovulation day is the day before BBT rises. This is because your basal body temperature rises as your progesterone levels rise, but your body doesn’t start producing progesterone until the egg is released.
When you are looking at your chart (see my example below), you can determine ovulation day as the day before the BBT spike, but only after the body’s temperature has been higher for 3 days.
Ovulation Prediction Vs. Confirmation
Basal body temperature cannot predict ovulation. Although some people experience a “dip” in body temperature on ovulation day, this is rare, and dips and spikes naturally occur throughout the entire cycle.
It is only after the third day of a slight increase in temperature that you can pinpoint ovulation. A spike in BBT will confirm that you have ovulated as your body is producing progesterone.
If you want to accurately predict ovulation before it happens, use an ovulation predictor kit (I’ll give you the rundown on those here) and track your cervical mucus and position. Tracking your BBT and cervical mucus is usually referred to as the symptothermal method of birth control.
By recognizing patterns in your BBT chart, using ovulation tests, and tracking cervical mucus, you should be able to predict when you are going to ovulate in a reliable way.
If your egg was fertilized, the next phase is implantation, where the egg attaches to the wall of the uterus.
Some people see a dip in BBT during implantation, about 5-7 days after ovulation. This is a one-day dip that may or may not fall below temperatures in the follicular phase. You will see your temperatures jump right back up the next day.
The reason for this dip is unknown and is not an accurate predictor of pregnancy. Many women who were not pregnant also experienced a dip in BBT in their luteal phase.
One possible theory is the production of estrogen during your cycle. Estrogen lowers the body’s temperature and progesterone raises it. Right before ovulation estrogen is at its highest, and usually BBT is at its lowest temperature. After ovulation progesterone rises, raising the temperature. During the luteal phase, there is a second rise in estrogen which could account for the dip. Pregnancy also causes a rise in estrogen.
Because both pregnant and non-pregnant women experience dips in BBT after ovulation, it isn’t a reliable way to tell whether you are pregnant. If you’re interested in what is going on in your body after ovulation with other signs that you might be pregnant, check out this article.
Using BBT for Pregnancy Planning
In conjunction with OPKs and cervical mucus, BBT charting can be a helpful tool in determining when your body ovulates during a regular cycle. Once you know your ovulation date, you can determine your fertile window: the 5 days before ovulation and ovulation day.
If you are TTC you want to use BBT to time sexual intercourse during the most fertile days. You can also use ovulation predictor kits to detect your LH (luteinizing hormone) surge that happens before ovulation.
You can continue tracking BBT after ovulation until you get your next period. Your body heat will go back down until your next cycle when the next egg is released.
It can be exciting to see a dip in temperature around days 5-7 after ovulation, but don’t get too excited, as it doesn’t always indicate a potential pregnancy. You can take a pregnancy test around 9 DPO (days past ovulation) and continue testing until you get your period or a positive test. If you need to test for pregnancy sooner, your healthcare provider can do a blood test.
In conclusion, basal body temperature (BBT) is a method used to track changes in body temperature throughout the menstrual cycle. BBT usually ranges between 96 and 98 degrees Fahrenheit before ovulation, and it rises by 0.5 to 1 degree after ovulation, known as the thermal shift. BBT rises approximately 24 hours after ovulation. However, BBT alone cannot predict or determine the exact timing of ovulation. It can only confirm ovulation after a sustained rise in temperature for at least three consecutive days. Therefore, relying solely on BBT as a fertility awareness method or a form of birth control may be unreliable. It is recommended to track BBT along with other methods such as monitoring cervical mucus and using ovulation predictor kits for more accurate prediction of fertile days. As with any family planning, make sure you are following the advice of a doctor.