Basal body temperature charting is actually amazing. I think it’s the coolest thing ever. I mean, how many people do you know who can tell you exactly when they ovulated? Or can tell you to the day when their period is coming if they’re not on the pill?
What is basal body temperature? And why does it matter?
Basal body temperature is a measure of your resting metabolism. For women, our metabolism changes after we ovulate. Our resting body temperature actually increases after ovulation as our bodies prepare for pregnancy. If you take your temperature each morning before you get out of bed and record it, you’ll notice an obvious shift in your temperatures after your ovulate.
This happens because of hormonal changes. After you ovulate, your ovaries produce progesterone, and progesterone causes your body temperature to rise in your post-ovulatory phase.
In order to get an accurate basal body temperature reading you’ll need a thermometer that measures your temperature to a 10th of a degree (i.e. 97.3 F or 37.4 C). You don’t need a fancy thermometer to do this, so don’t overthink it!
Myth Busting
Unfortunately many people still believe that basal body temperature changes will help a woman to predict when she’ll ovulate. The temperature shift can only happen after a woman ovulates so it doesn’t predict anything. But a woman can use her temperature shift to confirm that she ovulated, to accurately identify her due date, and to pinpoint when her period will come.
How to Check Your Basal Body Temperature
There are 3 simple steps to getting an accurate basal body temperature reading each day, so here goes…
1. Take your temperature first thing in the morning before you get out of bed each day
You’ll need at least 5 hours of consecutive sleep so that your body can “reset” itself back to it’s resting metabolic rate. If you jump out of bed and go to the bathroom before you take your temperature that could change the reading.
2. Leave your thermometer in place for 10 minutes before pushing the button
This is one that most people don’t know. Those cool digital thermometers beep so quickly. They’ll give you a temperature reading within 15 seconds, but if you take your temperature 3 times in a row you’ll probably get 3 different temperatures. This is because your thermometer has to be in place long enough to give an accurate reading of your temperature.
3. Take your temperature around the same time every morning
Many people take this to the extreme. I don’t think you have to go overboard here. It does matter when you take your temperatures. Your temperatures rises about a half a degree for every additional hour of sleep that you get, so it does matter when you take your temperature. However if you take your temperatures around the same time each day within about an hour or so, that’s good enough. If you get up much later or earlier one morning, still take your temperature and make a note of what time you got up. This will help you interpret your temperature chart later on.
How do I know if I ovulated?
A general guideline is that if you have 3 temperatures that are higher than your previous 6 temperatures that means you’ve ovulated. Your temperature shift will be obvious. You’ll be able to see two sets of temperatures, your low pre-ovulatory temperatures and your high post-ovulatory temperatures. If your temperatures are all over the place and you don’t see a clear shift you probably didn’t ovulate. So hang in there and keep tracking your temperatures until you see a clear temperature shift!
Now I want to hear from you! Have you ever taken your basal body temperature in the morning? What are your tips for getting an accurate BBT reading? What is your favorite thermometer? Join the conversation in the comments below!
I work two night shifts a week. How can this affect my charting?
Hi Lauren, if you work night shifts, you can still take your temperature after 5 consecutive hours of sleep. You may notice that your temperatures are more erratic, so even more reason to follow the steps outlined above to get an accurate temperature!
I used to oral temp and at first stressed so much about getting it right I kept waking all night thinking it was time to temp. Eventually I settled into a routine and it worked OK for me as I generally had a regular sleeping pattern. But then Tempdrop came along and I just had to try it. It makes temping a breeze. No more having to wake at the same time. No more stressing about not getting enough sleep before temping (you can have irregular sleep patterns and it will still work). It takes all the pressure away. I love it. Worth the money.
If we don’t have ten minutes to lay in bed with a thermometer in our mouth (active mornings with a toddler), what other methods can we use? Is the armpit an option?
You can leave it for as long as you have. Many women are turning to devices that measure average sleep temperature (temp drop, ava) for that reason. You may also have to rely on your cervical mucus when your temperatures aren’t readable.
Is it okay to drink water throughout the night? Will that mess with my temperature?
I’ve been getting multiple readings, I couldn’t figure out why…I’m hoping the 10 minutes will help! How do I know if it’s my thermometer that’s off? And why not 5 minutes? Just curious 🙂
Hi Mary! This suggestion comes from years of experience working with hundreds of women! It works 🙂 L.
What happens if you see a spike for 3 days and then the 4th day is about 0.3 degrees lower? I do have varying days of waking because of working at the hospital 3 days a week so I have to get up at 5am and I normally wake up between 7 and 7:30. I haven’t tried warming the thermometer before taking my temp but I’m going to tomorrow!
Have a listen to this podcast episode! http://fertilityfriday.com/258
Can I use just temperature to confirm Ovulation or do I need to use cm too? TTA
That depends on which method of fertility awareness charting you follow. Some are mucus only, some are BBT only, and others are sympto-thermal (both CM and BBT). It’s up to you. I’ve found doing a cross-check with the sympto-thermal method to be most effective.
Where can I find a thermometer that isnt automatically going to go off on it’s own programmed timing? They all seem to be around the 1-3 min timing. I would really like to find one that I can leave in for the full 10 minutes and then have it give me a reading when I tell it too:)
Thank you so much Lisa for the work you do!
Hi Victoria, you don’t need a special thermometer. You can place the thermometer in your mouth for 10 minutes, and then click the button to turn it on so it can give an accurate reading after you’ve warmed it up.
I realized my question was a little silly after the fact:) I had purchased the femometer vinca which automatically turns on as soon as you take it out of its case, and for that reason trying to get a 10 minute reading was tricky…it was a much more fancy of a gadget than I needed, I picked up a more simple straight forward one that I’m loving! Thank you so much for your response and pointing me on the right direction:)
Hello! I just want to make sure I’m reading correctly.. I typically get up at 4:45am.. If I wake up to use the bathroom anytime after midnight, my temp could be wrong when I take it? I’m trying to drink more water to help with my CM, but it seems it could be making me misread my temps ?? Thank you!
I get up to nurse my baby in the morning when he wakes up and then go back to sleep for a bit while my husband watches him. The time he gets up varies within 1.5 hours. I’ve been trying to take it when I hear him wake up but it doesn’t give me enough time to warm it up first.