By Kirsten Karchmer

Friday Questions & Answers: You down with BBT?

Happy Friday! When we first opened up our Friday Question and Answer blog, we got tons of great questions. One of the topics that we received the most questions about was basal body temperature (BBT). Today, Conceivable Founder Kirsten Karchmer, answers some of the most frequently asked questions about BBT. 

What is BBT?

BBT stands for basal body temperature. Basal body temperature is the body’s resting temperature and an important indicator of your fertile potential.


How do I track my BBT?

The easiest way to track your BBT is to take take your temperature by mouth each morning just after you wake up, but before you get out of bed or move around too much. The less you move before taking your temperature, and the more consistent you are about taking it at the same time everyday, the more accurate these readings will be.


Do I need a fancy thermometer to track my BBT?

Nope - any BBT thermometer from the corner drug store will work. While there are a lot of nifty thermometers out there, a fancier thermometer isn't going to make you any more fertile. Only understanding what your BBT patterns mean, and taking action to improve them, can actually change your chances of getting pregnant. You could take your BBT with a unicorn horn, but it's not going to magically change your fertility.


I don't like tracking BBT, so seriously, why is BBT so important?

Your BBT is important because it gives you a snapshot of hormonal activity across your menstrual cycle. During each phase of the cycle, different hormones become dominant, each with its own effect on body temperature. By tracking your temperature, you can see which hormones are active and if the interactions between hormones are working smoothly. This can give you really important insight into what's going on with your cycle. Tracking BBT doesn't have to be difficult or annoying, and it gives you really important data!


Wait, I thought my body temperature was always supposed to be 98.6º F.

98.6º F is your active body temperature. When you’re up and moving around, your body is expending energy, which is released in the form of heat that drives body temperature up. Your basal body temperature should generally run a little lower, from about 97.2º F before ovulation to above 98º F afterwards.


Why does my BBT change throughout the month?

Different hormones produce different thermal effects throughout the menstrual cycle. In the beginning of your cycle, a balance between estrogen and follicle stimulating hormone (FSH) should result in a relatively low temperature (97.2-4º F). After ovulation, progesterone causes temperatures to surge upwards of 98º F. These changes are completely normal and indicate healthy hormone function.


What can changes in BBT tell me?

Some changes in BBT are totally normal and healthy, like the rise in temperature that most women see after ovulation. Other changes, like a lot of variation from day to day, or temperatures outside of the healthy range above, may indicate that hormone function isn’t optimal. Conceivable can help changes and provides valuable feedback to help you address them.


Can my BBT tell me when I’m fertile?

It can certainly help! Tracking BBT over time helps establish a pattern of ovulation. For most women, ovulation will occur about 14 days before your period starts. This should coincide with a big rise in BBT. Some women will also see a temperature “dip” just before ovulation occurs and experience a change in the quality or quantity of their cervical fluid.

I don't recommend using BBT as your only predictor of ovulation though. You're most fertile right before you ovulate, so if you wait for those BBT temperatures to rise, you're missing out on your most fertile days.


Friday Q&A: Your Questions Answered.

Every Friday, we answer your great questions about fertility, the Conceivable Program, or whatever else you're wondering about. Don't be afraid - fertility is really complicated and can be super confusing - there are no silly questions! Ask away!

You can email us your questions at and be sure to check back next week to see the answers! We'll see you next Friday with a new Q&A. 

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