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Body Basal Temperature: Most Asked Questions

You may have heard about the concept of fertility awareness. It refers to tracking what's happening inside your body and what that means for your fertility. There are many different methods of tracking fertility, and some of the common methods are basal body temperature (BBT), ovulation predictor kits, cervical mucus changes, and checking the position of your cervix.

One that we like to have patients track in our clinic is their BBT, which shows trends through all 2 different phases (follicular and luteal) of a woman's cycle and reveal what part of her cycle needs to be addressed.

What is BBT?

The basal body temperature indicates your core body temperature when resting.

Why should I take my BBT?

Your goal is to find out the health of your menstrual cycle and track when or if you're ovulating, which will help you time intercourse if you are trying (or not) to get pregnant. You will also learn the patterns of your cycle. If you are working with a health professional, tracking your BBT can also help you understand your hormonal health.

In my clinic, having patients track their BBT serves many purposes. Besides giving indication to if their ovulation status, it also allows me to see the imbalances in their cycle relating to Chinese medicine diagnosis. Another great tool that it serves is to confirm pregnancy or indicate when the next menstrual cycle will begin.

What are the factors that affect BBT readings?

Your BBT is influenced by many factors, including hormonal fluctuations during the menstrual cycle.

Your BBT can increase slightly around the time of ovulation, and it may remain elevated for the duration of your cycle after ovulation.

Other factors can influence your body temperature aside from your menstrual cycle;

  • Fever, fever caused by an infection

  • Illness

  • Hormonal contraception use

  • Drinking alcohol the night before

  • Hypothyroidism (decreases BBT)

  • Hyperthyroidism (increases BBT)

  • Physical or emotional stress

  • Drug use

  • irregular sleep pattern or poor sleep quality

  • Changes in your waking schedule

  • Room temperature changes

  • Medications that affect body temperature, such as fever medications

  • Change of weather

  • Travel, jet lag

  • Certain medical disorders

When is the best time to take my BBT?

To ensure accuracy in your body temperature readings, take your temperature immediately upon waking up each morning.

And to accurately read your basal body temperature, you should get at least three to four hours of uninterrupted sleep.

You should do this at the same time each morning. If you delay taking your temperature, it could result in an abnormal body-temperature reading on your BBT chart.

What is the average BBT?

The average range of BBTs is between 97.0-97.7 before ovulation and a temperature of 97.7-99.0 after ovulation. A woman's temperature should not bounce around more than .5 degrees in the follicular phase, nor should it drop below the cover line during the luteal phase (after ovulation).

How can I tell if I ovulated?

On the day after you ovulate, you should see a shift of 0.5 to 1.0 degrees in your BBT, which should last until your next period. Ovulation most likely happens when a slightly higher temperature remains steady for three days or more.

How long should my temperature stay up after ovulation?

Ideally, your temperature should stay up to 14 days after ovulation; some doctors say anything over 10 days is acceptable.

What should my BBT be if I'm pregnant?

After ovulation, your body's basal body temperature (BBT) will generally rise to 98s degree. Your BBT will remain elevated until the beginning of your period. When your period begins, the temperatures return to their average pre-ovulatory level, which ideally should be in the mid 97s degree.

If you're pregnant, your BBT will remain high during the luteal phase. This can last up to 16 days after ovulation; if it's been longer than 2.5 weeks since ovulation and you're still seeing elevated temperatures, this may indicate that you are pregnant.

Can BBT predict miscarriage?

A slow decrease in your temperature may signify an impending or completed miscarriage or an otherwise nonviable early pregnancy. If you are about to have a miscarriage, or if you are in the process of one, an increase in your BBT above 99 degrees Fahrenheit could indicate an infection in your uterus. If you are suspecting a possible miscarriage, please seek professional help and run the necessary tests (do not rely on the internet for answers. The info here is for educational purposes only and should not be used to medically diagnose anyone).

What is the best basal body thermometer?

You can use any digital oral thermometer or a thermometer specifically designed to measure BBT.

A regular digital thermometer will work just fine if it tracks your temperature in the 10th digit.

What does the temperature dip in luteal phase mean?

If you drop a few tenths of a degree—for example, from 97.9 to 97.6°F (36.6°C to 36.4°C)—in your basal body temperature for one day, you may be experiencing an implantation dip.

While a one-day temperature drop is more likely to occur during pregnancy, it's not a definitive sign that you are pregnant.

You may see a slight dip on your BBT chart almost every month on the seventh or eighth day after you ovulate. Even if you are not pregnant, one reason your temperature dips during your luteal phase is a slight estrogen surge.

What is cervical mucus?

Cervical mucus is a vaginal discharge produced by the cervix—your cervical mucus changes throughout your menstrual cycle in response to fluctuating hormone levels. Checking your cervical mucus and keeping track of these changes can help you tell when you're most fertile.

BBT Charting and Cervical Mucous

Cervical mucous is a helpful indicator of fertility, offering the information you can use in conjunction with temperature charting to indicate ovulation. The mucous produced by the cervix is slippery and looks like egg whites before ovulation. This mucous is helpful for sperm to survive and reach the egg for fertilization. High levels of progesterone cause cervical mucous to be more opaque, dry, or have a paste-like consistency that happens right before and after menses.

How to test your Cervical Mucous:

  • Start testing your cervical mucous from day 6 in your cycle.

  • First, insert your finger at the entrance to your vagina and collect any mucous. If you did not get any, carefully insert your finger into the opening of your cervix.

  • On your BBT chart, label your mucus if it is Watery, Sticky, Creamy, or Egg White-like consistency.

  • The volume of your cervical mucus should be rated as either Light, Medium, or Heavy. Rating changes in your mucous becomes easier during your cycle, do not worry if you are unsure.

BBT Charting and Menstruation

During menstruation, label the color of your blood each day as either Light, Normal or Dark.

Light for light-colored watery blood. Normal for normal blood red colored blood. Dark for dark or brown or even purple-colored blood.

It will also help if you rate the volume of your menstrual blood as Light, Medium, or Heavy.

Fertility can be affected by various factors, including daily activities and environmental conditions. With BBT data collected from each patient, acupuncture or herbal treatments can be more effective in treating patients with fertility issues.

I hope I have answered your questions and taken some unknown factors out of the equation.

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