Skip to Content

How long after ovulation does BBT (Basal Body Temperature) rise?

This post contains affiliate links and is for general information purposes only. Please visit my disclosure policy for more information.

Wondering how long after ovulation does BBT rise? Here’s everything you need to know, especially if you’re looking to become pregnant (or hoping to avoid it)!

Whether you’re a first time mom looking to become pregnant or hoping to avoid it, tracking BBT (basal body temperature) can help you determine when you’re ovulating and your level of fertility.

This might sound complicated, but once you understand the ins and outs of your menstrual cycle, it’s actually quite simple. You can also utilize charts and apps to help streamline the process.

Below, you’ll find everything you need to know about BBT and ovulation.

Reasons to Track BBT for Ovulation

Pink heart represents an egg after ovulation with white faux sperm swimming towards it.

If you’re looking to become pregnant, it’s important to know when your fertile window starts and whether or not you’re ovulating. Basal body temperature changes can help to determine whether or not you’re ovulating, but can’t pinpoint the exact day of ovulation.

For the most accurate results, an ovulation predictor kit should be used. Predictor kits measure specific hormone levels in the urine. These elevated hormone levels are tied to unique phases of the menstrual cycle and changes in cervical mucus.

Still, BBT can provide valuable information regarding a woman’s fertility. Many women prefer to track BBT along with using a predictor kit to get more in-depth information about their cycles.

RELATED: How early can a pregnancy be detected?

Normal BBT Changes

In normal circumstances, BBT is slightly lower in the follicular phase (the first half of the menstrual cycle) and rises during the luteal phase (after the release of the egg). Most women experience an increase of about half a degree in temperature.

If there’s no pregnancy, this higher temperature should last until right before menstruation. With no fertilized egg, progesterone levels will drop, and your period will start.

Abnormal BBT Changes

However, if basal body temperature remains constant during a woman’s cycle, this may indicate a lack of ovulation. BBT tracking can reveal these absences and can also discover a condition called luteal phase defect. This is when insufficient levels of progesterone create higher temperatures at the start of ovulation, but then drop back off well before menstruation. This is typically a sign of poor fertility.

Most women with a regular menstrual cycle release eggs around 14 days before their period. But as mentioned, you’re not guaranteed to ovulate with every menstrual cycle. And if there are less than 13 days between ovulation and the first day of your period, you may experience reduced fertility.

If you notice any of these conditions, it may be time to speak with your doctor to discuss fertility and possible treatments.

NOTE: BBT can also help you avoid fertile days if you’re trying to prevent pregnancy.

How long after ovulation does BBT rise?

Color coded charts with recorded basal temperature readings and fertility markers for ovulation.

It can take as many as 3 days after ovulation to experience a temperature shift, but, this usually occurs within 12 to 14 hours. This is why BBT should not be solely relied upon to determine the start of ovulation. You might just miss your fertility window if your egg has already been released.

NOTE: Fertility is highest the 2 days prior to and on the day of ovulation. Keep in mind, eggs only survive for 24 hours, but sperm can live for 5 days. Experts recommend intercourse every other day starting 2-4 days prior to the anticipated day of ovulation.

How to Track BBT

The temperature spike after ovulation is very small and can’t register on a regular thermometer. You’ll need to purchase a special basal thermometer from the drugstore. These thermometers measure temperature changes in 1-tenth of a degree increments instead of the normal 2-tenths.

Here’s how to get the most accurate readings:

  • Keep your basal thermometer on your nightstand or close to your bed.
  • Take your temperature first thing in the morning while still lying in bed. You’ll need to measure your temperature around the same time every morning (within about 30 minutes).
  • If you’re using a mercury thermometer, be sure to shake them down at night or briefly dip them in cool water. Doing the motions in the morning can cause a rise in temperature. 
  • Don’t eat or drink anything (not even water) before you check our temperature.
  • You’ll need at least 3 solid hours of sleep to produce an accurate result, so no staying up all night!
  • Note other factors that can increase BBT, including: alcohol consumption, using a heated blanket, a cold or infection, heightened emotions and even jet lag.

When deciding on a basal thermometer, keep in mind, electric thermometers are easier to use, typically signal when peak temperature is reached, and can store information for future reference.

One of the easiest ways to track your cycle, predict ovulation days, and record your BBT is with an Ava bracelet.

RELATED: What week do pregnancy symptoms start?

BBT Ovulation Charting

Red, white and blue fertility chart and white and pink ovulation test stick.

To fully utilize BBT temperature readings, you’ll need to track your cycles for at least a few months. This will allow you to identify patterns that point to the time of ovulation. It’s best to use online charts and calendars or free phone apps to reduce error. These programs can also provide automatic alerts, indicating when ovulation likely occurred.

For best results, you should start charting on the first day of your period. Continue every morning throughout the entire cycle. Temperature levels may fluctuate here and there, but an overall picture should begin to emerge. Before ovulation, your average temperature should be lower than the readings afterward.

When you note at least three above average temperatures in a row, ovulation likely occurred on the day before the first high temperature.

NOTE: Some women may see a gradual rise in temperature vs a quick spike. This doesn’t necessarily affect your chances of getting pregnant. But, take note if temperatures are low through the entire luteal phase, or if the luteal phase is less than 10 days. This could signal signs of low progesterone and may indicate a fertility problem.

Does a prolonged rise in BBT indicate pregnancy?

If you become pregnant, BBT and progesterone levels will remain elevated throughout pregnancy.

You may also see a slight dip in temperature around a week after ovulation if you become pregnant. This is referred to as an implantation dip. Though, small dips in temperature are generally no more than a mid-cycle fluctuation.

RELATED: How long after sex does implantation happen?


What happens if BBT doesn’t rise after ovulation?

If you’re charting BBT and you don’t see a temperature spike in your cycle, it may mean you aren’t ovulating.

First, check to make sure your chart is correct and that you’re registering proper readings. Remember that you must check your temperature within 30 minutes of the same time each morning BEFORE you get out of bed and you need at least 3 solid hours of sleep.

Here are some other factors that can affect the accuracy of your readings:
– Alcohol consumption
– Using a heated blanket
– A cold or infection
– Heightened emotions
– Jet lag

If you still see no changes in temperature after insuring proper readings, you could be one of the small percentage of women who don’t experience a BBT rise after ovulation.

To be sure, you can check with your doctor. They can perform tests to confirm whether or not you’re regularly ovulating.

What will BBT be if I’m pregnant?

On average, pregnancy BBT is between 97.6°F (36.4°C) and 98.6°F (37°C).

Why is BBT high after ovulation?

Most women experience a slight increase in BBT post ovulation. This process signals the release of progesterone, which causes elevated temperatures and prepares the uterus to be implanted with a fertilized egg.

The Bottom Line

Woman holds purple basal thermometer and app to record a rise in BBT after ovulation.

How long after ovulation does BBT rise?

The bottom line:

  • Basal body temperature typically elevates 12-14 hours post ovulation, but can take up to 3 days.
  • In normal circumstances (and without a pregnancy) BBT will stay elevated 10-14 days post ovulation, up until the start of your period.
  • Basal body temperature is a great way to help track ovulation to both plan and avoid pregnancy.
  • It can also help determine certain fertility problems that reduce the chances of becoming pregnant.

Plan to use a BBT chart along with a ovulation predictor kit for the most accurate results. And be sure to track your temperatures for a least a few cycles to get an accurate view.

If you want a device that will track everything for you, consider investing in an Ava bracelet. They even have an option with a 6- and 12-month money-back guarantee if you’re not pregnant within that timeframe.

If you’re having trouble conceiving, talk to your doctor for more guidance.

Want More?

If this post was helpful, be sure to check out:

Your Turn

If you have more questions about how long after ovulation does BBT rise, let me know in the comments!

Pinterest graphic with text and woman holding basal thermometer and app to record BBT.