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What Is Basal Body Temperature and Should I Use It to Track My Fertile Window?

Clara Siegmund
Clara Siegmund

Tracking your basal body temperature may help you know if you’ve ovulated, but using this measurement in combination with other fertility tracking methods provides a better picture of your fertile window.

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Apr 25, 2023
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Tracking your basal body temperature may help you know if you’ve ovulated, but using this measurement in combination with other fertility tracking methods provides a better picture of your fertile window.

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Tracking your basal body temperature may help you know if you’ve ovulated, but using this measurement in combination with other fertility tracking methods provides a better picture of your fertile window.

Basal body temperature (BBT) is your body temperature when you’re fully at rest. Many people record their BBT as a way to track their fertility. Essentially, you take your basal body temperature every day to monitor increases that may indicate ovulation. Knowing when you’ve ovulating can help you determine when you’re most fertile, and most likely to get pregnant.

>>MORE: How Can I Tell If I'm Ovulating? How to Find and Test Your Fertile Window

But does BBT tracking really work to help you get pregnant? The short answer is: yes and no.

What is basal body temperature?

You may have already heard of fertility awareness-based methods of family planning. These methods, also called natural family planning methods, can be both a form of contraception or a way to achieve pregnancy. Basal body temperature is one of these methods that aims to help you determine when you’re most fertile. A person using fertility awareness-based methods tracks different signs of fertility throughout their menstrual cycle. Factors to monitor include:

  • Your cervical mucus
  • Your basal body temperature
  • The length of your menstrual cycle

For factors like your cervical mucus and your basal body temperature, hormonal changes throughout your cycle cause detectable physical changes that occur before and after ovulation.  

Take your cervical mucus, for example. Before a developing follicle is released during ovulation, it produces a type of estrogen called estradiol. This hormone facilitates the production of a clear, stretchy cervical mucus that helps sperm travel through the cervix. This cervical mucus is often called “egg white mucus” and generally appears about 3 to 4 days prior to ovulation.

Your BBT is your body temperature when you’re fully at rest. Like with cervical mucus, your basal body temperature is also influenced by hormones. Following ovulation, progesterone is released to prepare the body for a potential pregnancy. This hormone then tells your hypothalamus to increase your body temperature.

What should my basal body temperature be?

For most people, body temperature prior to ovulation varies between 96°F and 98°F. If you record a BBT higher than the previous six days for three days in a row, it can be an indication that you’ve ovulated. The rise in temperature is small: for many people, BBT increases around 0.5°F after ovulation. In some people, however, a distinct temperature change may not occur.

How do you track your basal body temperature?

Some people track their BBT to help them determine their fertile window. Your fertile window is the time in your cycle when you’re most likely to get pregnant.

Using the BBT tracking method is relatively simple on paper. Here’s what you need to do:

  1. Get a digital thermometer and make sure it measures temperature to at least one-tenth of a degree (two decimal places). You can’t go wrong if the packaging indicates that the thermometer is intended for measuring basal body temperature.
  2. Take your BBT every morning as soon as you wake up. Taking your basal body temperature at the same time, from the same place in your body, before you do anything else will give you the most accurate results.
  3. Record your temperature readings every day. You can do this on paper or using fertility tracking apps.
  4. Establish a baseline over time and track patterns so that you can understand when in your cycle you’re most fertile.

You first need to know what your body temperature usually is in order to recognize when it increases, and determining this baseline takes time. Generally, you will need to track your BBT over the course of multiple menstrual cycles to get a sense of your body’s patterns and find your fertile window.

The BBT tracking method requires vigilance and organization, and it’s easy to get some of the details wrong.

Should you use basal body temperature tracking to find your fertile window?

So, can tracking your BBT truly help you understand when you’re most fertile? The answer isn’t that straightforward, and there are both upsides and downsides to using BBT tracking as a fertility tracking method.

The pros

Accessible

There’s a lot to like about basal body temperature tracking. First off, it’s inexpensive. You don’t need special equipment other than your BBT thermometer, a relatively easy to find tool that generally costs under $20. And you don’t need to make or go to a doctor’s appointment: you can track your basal body temperature from the comfort of your own bed.

Non-invasive

Additionally, it’s a non-invasive method of fertility tracking. There are no surgical procedures required, no medication, no blood tests—it’s as simple as sticking a thermometer in your mouth (or rectum, or vaginal canal) and recording your temperature.

The cons

Basal body temperature tracking also has quite a few drawbacks as a method for understanding your fertility.

Difficult to get consistent readings

For example, your BBT can be a bit finicky. For accurate BBT readings, you have to take your temperature first thing in the morning. Little things like getting out of bed, using the bathroom, eating, drinking, or even talking can affect your BBT. If you take your temperature at 8 a.m. one day and 10 a.m. the next, this difference in time can also alter your results. The way to get the most exact readings is to take your temperature right when you wake up, at the same time every day, and this is sometimes easier said than done.

Hard-to-read results

Even if you follow BBT measurement instructions exactly, the results may not tell you much. In some people, a rise in temperature may not occur until 3 days after ovulation. Other people may not experience a change in temperature at all. This makes it harder to determine your fertile window based on your basal body temperature.

Easily affected by outside factors

Factors other than ovulation can also cause your BBT to fluctuate, which can make the method unreliable. If you’re monitoring your fertility with BBT tracking alone, it can be difficult to know if the changes in temperature that you record are caused by ovulation, or by something else.

Other factors than can affect your BBT include:

  • Health changes such as illness or fever
  • Gynecological disorders
  • Emotional or physical stress
  • Alcohol consumption
  • Sleeping too little or too much
  • Seasonal changes or changes in climate
  • Changes in room temperature
  • Shift work
  • Travel
  • Changes in time zones
  • Certain medications

>>RELATED: Learn how alcohol can affect your fertility.

Basal body temperature can also be tough to track for people with irregular menstrual cycles. It’s hard to find patterns in your body temperature when your month-to-month changes frequently, and this can make your BBT an inconsistent measurement.

It’s also important to note that because the rise in BBT occurs after ovulation, it’s likely that you’re no longer fertile by the time you note a change in your temperature. In fact, it’s more accurate to say that an increase in your BBT is the sign that your fertile window has ended.

Even under the most reliable circumstances, tracking your BBT to understand your fertility involves a bit of guesswork. In most cases, BBT tracking alone is an insufficient method for determining when you’re most likely to get pregnant.

Combining basal body temperature tracking with other ovulation tracking methods

Many doctors still recommend using your basal body temperature to track your fertility, particularly for its low-cost and non-invasive nature. To truly understand when you’re most fertile, however, it may be useful to combine this method with other forms of fertility tracking.

At-home fertility testing kits are a great option for getting a more in-depth look at your fertility. Oova offers at-home urine test kits that analyze your body’s levels of luteinizing hormone (LH), PdG (a metabolite of progesterone) and E3G (a metabolite of estrogen), three hormones that are essential to ovulation and pregnancy. With Oova test strips and the Oova app, you can get detailed information about your fertility window and whether or not you’ve ovulated.

Instead of thinking of basal body temperature tracking as the way to track your fertility, think of it as one tool in your toolbox. You’re most prepared when you use a combination of the tools available to you. Combining BBT tracking with other fertility tracking methods, like at-home fertility testing kits, can give you a fuller picture of your fertility and help set you up to get pregnant.

About the author

Clara Siegmund
Clara Siegmund is a writer, editor, and translator (French to English) from Brooklyn, New York. She has a BA in English and French Studies from Wesleyan University and an MA in Translation from the Sorbonne. She is passionate about literature, reproductive justice, and using language to make information accessible.‍

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https://www.oova.life/blog/progesterone-supplementation-guide
Can I take progesterone if I'm breastfeeding?
Yes, progesterone is generally safe while breastfeeding and doesn't significantly affect milk supply. However, always discuss with your healthcare provider before starting any hormone supplementation while nursing.
https://www.oova.life/blog/progesterone-supplementation-guide
Is it safe to take progesterone throughout pregnancy?
Yes, when prescribed by your healthcare provider. Progesterone supplementation in early pregnancy is safe and can reduce miscarriage risk in women with low progesterone or a history of pregnancy loss. Most providers continue supplementation through the first trimester (weeks 10-12) when the placenta takes over.
https://www.oova.life/blog/progesterone-supplementation-guide
Can progesterone supplementation cause weight gain?
Progesterone can cause temporary water retention and bloating, which may show up as a few pounds on the scale, but it doesn't cause true fat weight gain. Most women don't experience significant weight changes from progesterone supplementation.
https://www.oova.life/blog/progesterone-supplementation-guide
Can I switch from pills to suppositories or vice versa?
Yes, but only under your doctor's guidance. The dosing and timing may need adjustment when switching between forms since they're absorbed differently. Never switch on your own, especially if you're pregnant or undergoing fertility treatment.
https://www.oova.life/blog/progesterone-supplementation-guide
Will progesterone supplementation delay my period?
Yes, progesterone keeps the uterine lining intact, so if you're not pregnant and continue taking progesterone, your period will be delayed. Once you stop taking it, your period should start within 2-10 days. If you are pregnant, progesterone helps maintain the pregnancy and you won't get a period.
https://www.oova.life/blog/progesterone-supplementation-guide
Should I take progesterone pills orally or vaginally?
For fertility and pregnancy support, vaginal progesterone is usually preferred because it delivers higher concentrations directly to the uterus. For perimenopause or general hormone balance, oral progesterone often works well and is more convenient. Your doctor will recommend the best route based on your specific needs.
https://www.oova.life/blog/progesterone-supplementation-guide
When should I start taking progesterone after ovulation?
Typically, progesterone supplementation for luteal phase support starts 2-3 days after ovulation (confirmed by LH surge or temperature rise). Your doctor will give you specific timing based on your protocol. Some women start immediately after a positive ovulation test.
https://www.oova.life/blog/progesterone-supplementation-guide
What's better: progesterone cream or pills?
Pills (oral micronized progesterone) are generally more effective and reliable than creams because absorption from creams is inconsistent. For medical conditions like fertility issues, low progesterone, or HRT, prescription pills or suppositories are strongly recommended over over-the-counter creams.
https://www.oova.life/blog/low-vs-high-progesterone-symptoms
How can I tell if I have low or high progesterone?
The only definitive way to know is through hormone testing via blood tests or at-home urine tests that measure progesterone metabolites. However, symptom patterns can provide clues: anxiety and irregular periods suggest low progesterone, while bloating and extreme fatigue suggest high progesterone.
https://www.oova.life/blog/low-vs-high-progesterone-symptoms
When during my cycle should I test progesterone levels?
Test progesterone levels during the luteal phase, typically 7 days after ovulation or around day 21 of a 28-day cycle. This is when progesterone should be at its peak, making it easier to identify if levels are too low or too high.
https://www.oova.life/blog/low-vs-high-progesterone-symptoms
What are the main differences between low and high progesterone symptoms?
Low progesterone typically causes irregular or heavy periods, anxiety, hot flashes, and sleep issues. High progesterone causes bloating, fatigue, intense breast tenderness, and depression-like mood changes. Low progesterone symptoms persist throughout your cycle, while high progesterone symptoms are most intense during the luteal phase.
https://www.oova.life/blog/low-vs-high-progesterone-symptoms
Can you have symptoms of both low and high progesterone?
Some symptoms like breast tenderness and mood changes can occur with both low and high progesterone, making it confusing. However, the timing, intensity, and accompanying symptoms differ. Hormone testing is the best way to determine which imbalance you're experiencing.
https://www.oova.life/blog/10-dpo
Can stress affect 10 DPO symptoms?
Yes, stress can worsen or mimic 10 DPO symptoms. Stress increases cortisol, which can cause cramping, fatigue, and mood changes similar to both PMS and early pregnancy. During the two-week wait, try stress-reduction techniques like gentle exercise, meditation, or spending time with loved ones.
https://www.oova.life/blog/10-dpo
Is it better to test at 10 DPO or wait?
It's better to wait until 12–14 DPO for more accurate results. Testing at 10 DPO often leads to false negatives because hCG levels may still be too low. If you absolutely can't wait, use a sensitive early detection test with first morning urine, and be prepared to retest in 2–3 days if negative.
https://www.oova.life/blog/10-dpo
What does implantation bleeding look like at 10 DPO?
Implantation bleeding at 10 DPO is typically light pink or brown, much lighter than a period, and lasts 1–2 days. It's often just spotting when you wipe or a few drops on a panty liner. However, only 15–20% of pregnant women experience implantation bleeding—most don't have any bleeding at all.
https://www.oova.life/blog/10-dpo
Why am I cramping at 10 DPO?
Cramping at 10 DPO can be caused by elevated progesterone (whether you're pregnant or not), implantation (if you're pregnant), or premenstrual cramping. Unfortunately, cramping alone can't tell you if you're pregnant since progesterone causes similar symptoms in both scenarios.
https://www.oova.life/blog/10-dpo
What are the chances of a BFP at 10 DPO?
If you're pregnant, you have about a 50–60% chance of getting a positive test at 10 DPO. This means there's a 40–50% chance of a false negative even if you conceived. Chances improve significantly by 12–14 DPO.
https://www.oova.life/blog/10-dpo
What DPO is most accurate for pregnancy testing?
14 DPO (the day of your missed period) is the most accurate time to test, with 99% accuracy. 12 DPO offers 80–90% accuracy. 10 DPO has only 50–60% accuracy. For best results, wait as long as you can—ideally until 12–14 DPO.
https://www.oova.life/blog/10-dpo
Is 10 DPO too early to test?
10 DPO is considered early for pregnancy testing. While some women get positives at 10 DPO, accuracy is only 50–60% if you're pregnant. For best results, wait until 12 DPO (80–90% accuracy) or 14 DPO/missed period (99% accuracy).
https://www.oova.life/blog/10-dpo
Can you have implantation at 10 DPO?
Yes, implantation can still occur at 10 DPO, though 84% of women have already implanted by this point. Late implantation at 10–12 DPO is normal. If implantation happens at 10 DPO, you won't get a positive pregnancy test for another 2–3 days.
https://www.oova.life/blog/10-dpo
What does a negative test at 10 DPO mean?
A negative test at 10 DPO does not mean you're not pregnant. It's very common to get negatives at 10 DPO even if you conceived. Your hCG levels may still be too low, or implantation may have occurred later. Wait until 12–14 DPO to retest for more accurate results.
https://www.oova.life/blog/10-dpo
Can you get a positive pregnancy test at 10 DPO?
Yes, but only about 50–60% of pregnant women will get a positive at 10 DPO. The other 40–50% have hCG levels that are still too low to detect. If you test negative at 10 DPO, wait 2–3 days and test again.
https://www.oova.life/blog/high-progesterone-symptoms
Can high progesterone cause weight gain?
Yes, elevated progesterone can cause temporary weight gain through water retention and bloating. This is a normal part of the luteal phase and early pregnancy.
https://www.oova.life/blog/how-to-increase-estrogen
Does stress affect estrogen levels?
Yes, chronic stress elevates cortisol, which can suppress estrogen production and disrupt hormonal balance. Stress reduction through meditation, yoga, adequate sleep, and self-care practices helps maintain optimal estrogen levels.
https://www.oova.life/blog/how-to-increase-estrogen
When should I consider medical treatment for low estrogen?
Consider medical intervention if natural methods don't improve symptoms after 3 months, if symptoms severely impact quality of life, if you're experiencing early menopause (before 40), or if you have fertility concerns. Hormone replacement therapy may be appropriate in these cases.
https://www.oova.life/blog/how-to-increase-estrogen
What are the signs that my estrogen is increasing?
Signs of rising estrogen include more regular menstrual cycles, reduced hot flashes, improved vaginal lubrication, better mood stability, increased energy, and improved skin elasticity. You may also notice reduced symptoms that originally indicated low estrogen.
https://www.oova.life/blog/how-to-increase-estrogen
Can exercise increase estrogen levels?
Yes, moderate exercise stimulates estrogen release and helps maintain hormonal balance. Aim for 150 minutes of moderate cardio weekly plus strength training twice per week. However, excessive exercise can actually lower estrogen, so balance is key.
https://www.oova.life/blog/how-to-increase-estrogen
How long does it take to increase estrogen naturally?
With consistent dietary and lifestyle changes, you may notice improvements in symptoms within 4-8 weeks. However, significant hormonal changes typically take 2-3 months. Tracking your cycle and symptoms can help you monitor progress.
https://www.oova.life/blog/how-to-increase-estrogen
What foods increase estrogen levels naturally?
Foods high in phytoestrogens can help increase estrogen naturally. The best options include flax seeds (high in lignans), soy products (tofu, tempeh, edamame), lentils, chickpeas, whole grains (oats, quinoa, brown rice), and garlic. These plant compounds mimic estrogen's effects in the body.
https://www.oova.life/blog/perimenopause
What helps relieve hot flashes quickly?
Cool environments, layered clothing, herbal teas, and medical treatments like gabapentin or HRT may help—depending on severity. Lifestyle changes like reducing caffeine and alcohol can also provide relief.
https://www.oova.life/blog/perimenopause
Are there tests to confirm perimenopause?
Yes. Tests measuring estradiol, LH, and FSH levels can indicate hormonal shifts—but diagnosis is often symptom-based since hormone levels fluctuate widely during perimenopause.
https://www.oova.life/blog/perimenopause
How do I know it's perimenopause and not something else?
A doctor may recommend hormone testing (like LH, E3G, and PdG) and track symptom timing. Diagnosis is often based on symptoms combined with age and menstrual pattern changes.
https://www.oova.life/blog/perimenopause
What's the earliest age perimenopause can start?
Some women begin experiencing symptoms as early as their mid-30s, though perimenopause typically starts between ages 38-45.
https://www.oova.life/blog/perimenopause
Does perimenopause affect mental clarity?
Yes. Brain fog and difficulty concentrating are common during hormone fluctuations in perimenopause.
https://www.oova.life/blog/TBD-10-symptoms-and-how-to-get-relief
What happens after the last sign of perimenopause?
After your final period, you enter postmenopause. You'll need 12 consecutive months without a period to confirm menopause. Many symptoms gradually improve, though some like vaginal dryness may persist without treatment.
https://www.oova.life/blog/TBD-10-symptoms-and-how-to-get-relief
When do perimenopause symptoms finally stop?
Some symptoms like brain fog improve after menopause, while others like hot flashes may continue for up to 10 years post-menopause. Vaginal symptoms often persist or worsen without treatment. Each person's timeline is different.
https://www.oova.life/blog/high-progesterone-symptoms
Is high progesterone a sign of pregnancy?
Yes, high progesterone is one of the earliest indicators of pregnancy. Progesterone levels rise significantly after conception to support the developing embryo and reach their peak during the third trimester.
https://www.oova.life/blog/TBD-10-symptoms-and-how-to-get-relief
Can you still get pregnant in late perimenopause?
Yes, you can still get pregnant during perimenopause as long as you're having periods, even if they're infrequent. Continue using birth control until you've gone 12 consecutive months without a period and have officially reached menopause.
https://www.oova.life/blog/TBD-10-symptoms-and-how-to-get-relief
Do symptoms get worse before perimenopause ends?
Yes, most perimenopause symptoms intensify in the final 1-2 years before menopause. Hot flashes peak around your final period, vaginal symptoms worsen, and mood changes increase. However, brain fog typically improves in late perimenopause.
https://www.oova.life/blog/TBD-10-symptoms-and-how-to-get-relief
How long does late perimenopause last?
Late perimenopause typically lasts 1-3 years before your final period. However, the exact duration varies significantly from person to person. You've reached menopause after 12 consecutive months without a period.
https://www.oova.life/blog/high-progesterone-symptoms
What are the symptoms of high progesterone?
High progesterone symptoms include fatigue, bloating, breast tenderness, weight gain, anxiety, depression, headaches, and food cravings. During pregnancy, you may also experience increased nipple sensitivity and muscle aches.
https://www.oova.life/blog/TBD-10-symptoms-and-how-to-get-relief
What are the first signs that perimenopause is ending?
The earliest signs include longer gaps between periods (60+ days), intensifying hot flashes that peak around your final period, and worsening vaginal dryness. These symptoms typically increase in late perimenopause before you reach official menopause.
https://www.oova.life/blog/high-progesterone-symptoms
When should I be concerned about high progesterone?
Consult a healthcare provider if you experience high progesterone symptoms outside your luteal phase when not pregnant, or if symptoms include severe pelvic pain, abnormal vaginal bleeding, or rapid weight gain while on hormone therapy.
https://www.oova.life/blog/high-progesterone-symptoms
How do you test progesterone levels?
Progesterone can be measured through blood tests at your doctor's office or at-home urine tests that measure PdG (a progesterone metabolite). Testing is typically done during the luteal phase, about 7 days after ovulation.

About the Oova Blog:
‍Our content is developed with a commitment to high editorial standards and reliability. We prioritize referencing reputable sources and sharing where our insights come from. The Oova Blog is intended for informational purposes only and is never a substitute for professional medical advice. Always consult a healthcare provider before making any health decisions.

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