Your basal body temperature (BBT) is your lowest temperature over the course of a 24-hour period, and it rises somewhat after you ovulate. You may track your basal body temperature over time using a specific thermometer to predict when you’ll ovulate and determine your most fertile days.
What is basal body temperature?
The lowest body temperature you have in a 24-hour period is your basal body temperature (BBT). When you’re at rest, it’s the temperature of your body. BBT usually rises somewhat shortly after you ovulate.
You can use your basal body temperature to predict when you’ll ovulate and the optimal days to have intercourse if you’re trying to get pregnant (or be inseminated). You can track your BBT while also keeping an eye on changes in your cervical mucus for better accuracy.
Keep in mind that the two to three days leading up to the increase in BBT are the most fertile. As a result, by the time you notice a temperature change, your best window for getting pregnant will have likely passed. This method, however, may help you forecast when you’ll be most fertile if you have regular menstrual cycles and track your BBT over time.
Keeping track of your BBT might also assist your doctor in determining the source of any reproductive issues.
How do I take my basal body temperature? Can I use a regular thermometer?
A basal thermometer, which is sensitive enough to register minute changes in body temperature, is required to provide an accurate reading. Glass or digital BBT thermometers are available in pharmacies and online. Although some digital ones can measure to the hundredth of a degree, all you actually need is one that can measure to the tenth of a degree (thermometers that only give readings to two-tenths of a degree are not accurate enough).
Take your temperature first thing in the morning, before you eat, drink, have sex, or even sit up in bed or place a foot on the floor, to get your BBT. Take a reading each morning around the same time and record it on a BBT chart (see below). Your BBT chart will be inaccurate if you don’t take your temperature right after waking up.
What is the normal basal body temperature?
Your BBT may range from 97.2 to 97.7 degrees Fahrenheit before ovulation. However, you should notice a 0.5 to 1.0 degree increase in your BBT the day after you ovulate, which should remain until your next period.
You may notice a spike in your temperature on other days, but if it doesn’t stay up, you haven’t ovulated yet.
Be aware that, aside from ovulation, the following factors can influence your BBT:
Pregnancy: Your basal body temperature will remain raised throughout your pregnancy if you become pregnant.
Fever: If you are sick with the flu or another disease, your general body temperature will rise, making your BBT unreliable.
Medications: Antibiotics and blood pressure medications, for example, might produce a spike in BBT.
Disease: Thyroid issues can result in a rise in body temperature.
Heat or exercise: Both exercise and hot weather can raise your body temperature.
What is cervical mucus?
Cervical mucus is cervix-produced vaginal discharge. Due to varying hormone levels, the volume, colour, and texture of your cervical mucus fluctuates throughout your menstrual cycle.
You can detect when you’re most fertile by checking your cervical mucus and keeping note of these changes. Here are some things to keep an eye out for:
- It’s possible that you won’t have any discharge for a few days after your period ends.
- After that, you may notice a hazy, sticky discharge for a few days.
- The amount of discharge increases in the days leading up to ovulation, becoming thin, slick, and stretchy (like egg whites). The sperm can move more easily through the cervix to the egg because of this consistency. These are the days when you’re most fertile.
- Mucus production decreases and thickens shortly after ovulation.
- You may then go several days without a period before your next period.
When you go to the bathroom first thing in the morning, check your cervical mucus, but you can check it at any time of day. Cervical mucus can sometimes be seen on the toilet paper after you wipe. To get enough mucus to inspect, you may need to enter a clean finger into your vagina (towards your cervix).
Keep in mind that some drugs, intercourse, lubricant use, and douching might alter the look of cervical mucus.
Ovulation charts: Tools for tracking your BBT and cervical mucus
This blank chart can be used to keep track of your basal body temperature. It can also be used to keep track of cervical mucous. After a few months of recording your BBT, you’ll be able to observe if your cycle has a pattern. If there is, you might be able to predict when you’ll ovulate next.
You’re ready to start charting once you’ve printed a few copies of our blank chart and purchased a basal thermometer.
Take a peek at our filled-in sample chart if you want to see what a chart looks like when it’s finished.
When looking at the sample chart, keep in mind that each woman’s cycle is unique, so yours may not appear exactly like the example or even be the same month to month.
How to chart your basal body temperature and cervical mucus
Are you ready to get started with your chart? How to do it is as follows:
- Fill in the date and day of the week under cycle day 1 when you get your period for the first time. Until the first day of your next period, keep a record of the dates of your cycle.
- Take your temperature using a basal thermometer first thing in the morning, before drinking, eating, having sex, or even sitting up in bed. Place a dot next to the temperature that corresponds to your daily thermometer reading. (Make a note of when you took your temperature as well.) Take it at the same time every morning if possible.) See how your basal temperature changes from day to day by connecting the dots.
- If you like, you can check your cervical mucous every day. Using the key at the bottom of the chart, record the type of discharge you find each day: P stands for period, D for dry, S for sticky, and E for egg-white-like.
- Look for a day when your BBT climbed 0.5 to 1 degree F and stayed high at the conclusion of your cycle. It’s likely that you ovulated on that day. It should be the day you first noticed egg-white-like cervical mucous. Your most fertile days are when you observe egg-white-like mucous.
- Keep track of these symptoms for a few months to observe if BBT and egg-white-like mucus increase at the same time each cycle. If you wish to get pregnant, you’ll be able to schedule which days to have intercourse.
- Have intercourse at least every other day during your most fertile time to increase your chances of conceiving.
What if charting doesn’t work for me?
There are other techniques to estimate when you’ll ovulate if charting sounds stressful or if you simply can’t make it work. You can use an ovulation predictor kit, for example, which checks your hormone levels and predicts when you’re going to ovulate.
If you have the time, you can have sex every other day throughout the middle two weeks of your cycle if you want a more low-key approach.
You can also use our ovulation calculator to determine when you’re most likely to become pregnant.
- How long after ovulation does BBT rise?
The temperature can take up to three days to rise following ovulation. However, most women’s temperatures rise on the same day or the next day after an ovulation predictor test goes positive, in our experience.
- What is the best basal temperature to get pregnant?
Before ovulation, most women’s basal body temperature ranges from 97 to 97.5 degrees Fahrenheit; following ovulation, it normally ranges from 97.6 to 98.6 degrees Fahrenheit.
- How long before ovulation does BBT drop?
BBT stays in the lower range during the follicular phase of the cycle, often between 97 and 98 degrees Fahrenheit (36.1 to 36.6 degrees Celsius), until one day before ovulation, when it hits its lowest value.
- Can you get pregnant on day of temperature rise?
Although sperm can live up to five days in your reproductive system, you’re most fertile two days before your basal body temperature increases. This is the time to have sex if you want to get pregnant.