Your Basal Body Temperature

When your basal temperature goes up it means you've ovulated…and when it stays up, it often means you're pregnant! Here's how to use it to track your fertility:

One of the three things you watch for while charting your fertility is your daily temperature. You don't take this temp any old time, however.

(NOTE: Want the Top Easy Steps to Boosting Your Fertility? Use these 5 simple, evidence-based steps to get pregnant and carry your healthy baby to term. Get them here.)

Top Fertility Tips

Take it first thing in the morning, before you do anything else.

Basically you need to wake up, reach over to your bedside, grab your thermometer, and pop it in your mouth.

Get up and go about your day after the beep!

I highly recommend you use a digital thermometer because it won't break, it's easy to use, and it will store your temperature. This is handy – you take your temp then put your thermometer down while you get up, get dressed, and wake up a little. Then you come back and check what your temp was.

You plot these early morning temperatures out on a graph – included as part of your fertility chart. You “connect the dots” you plot out each morning and watch what your temperature does over the course of your cycle.

Starting Off

Your basal body temperature isn't obviously useful at the beginning of your cycle. It will be “low” in relation to what the temperature is later in your cycle. Exactly what “low” is, however, varies from woman to woman.

basal body temperature chart

It's good to note where your temperature is at because if you're having problems getting pregnant your temperature can give you a clue about what's going on(it can hint at thyroid and endocrine problems, for example.)

But generally your lower temperature just sets the benchmark for your post-ovulation basal body temperatures. You use these temperatures to set the “coverline.” After ovulation your temps will jump above the coverline until your next cycle. If you get pregnant, they'll usually stay above the coverline!

Setting the coverline can sometimes be confusing. It's one of the reasons I prefer to let the computer figure things out – I use charting software to keep track of my cycles.

Drawing the Coverline*

  1. Pay attention to the previous six days at any point in your cycle – notice the highest temp of the six.
  2. Identify the first day your basal body temperature rises at least two-tenths of a degree higher than that previous highest temp.
  3. Go back and highlight the six temps before the rise
  4. Draw the coverline one-tenth of a degree above the highest of those six previous high temperatures

I have a free, printable fertility chart for you. To see the coverline click for a full sample chart.

Ovulation and Beyond

When your temperature jumps above the coverline for three days you can feel confident ovulation has occurred.

Because your temperature does not jump until ovulation has occurred, basal body temperature is usually not used to predict ovulation – it confirms ovulation.

Some women, however, find that their temp takes a slight “dip” the day before ovulation. Watch your charts and see if this pattern is true for you.

After you've ovulated your temperature remains high due to high progesterone levels in your body.

As noted above, if you've successfully conceived your chart will tell you. Eighteen (18) days of high temperatures almost always indicate pregnancy. My charting software, Ovusoft, marks the 18th high temperature with a little duck. I think it's incredibly cute 😉

If you haven't conceived this cycle your temperature will often drop at the end of the cycle, letting you know your period is on the way. Sometimes it will stay high through the first couple of days of your next cycle due to progesterone.

Your temperatures after ovulation are very helpful. If you have high temperatures for eighteen (18) days you're most likely pregnant. If you start a period after having 18 days of high temperatures you have most likely had an early miscarriage.

If you have light spotting but your temperature continues to remain high you could in fact be pregnant.

All of this information is very useful if you're trying to conceive or trying to determine causes of infertility.

Other Benefits

Your basal body temperature, as noted above, can help you “troubleshoot” your cycle (and your body). If you're having issues conceiving, or you feel you often have low energy levels, pay close attention to your temperatures.

Low or erratic temperatures could indicate thyroid or endocrine issues – issues that can often be corrected nutritionally or nutritionally in combination with light hormone support.

If you decide to visit a practitioner about infertility your finished temperature graphs can greatly help the two of you to hone in on your issues and determine and appropriate plan of action for you.

(NOTE: Want the Top Easy Steps to Boosting Your Fertility? Use these 5 simple, evidence-based steps to get pregnant and carry your healthy baby to term. Get them here.)

Top Fertility Tips

Charting your temperature is a simple and important part of starting to understand your body and your cycle. It lets you know ovulation has occurred and indicates pregnancy (or confirms pregnancy – I know you're going to want to test before 18 days post ovulation!!)

  • These coverline rules are taken from Toni Weschler's amazing book Taking Charge of Your Fertility. I highly recommend you get a copy of the book and keep it on your bookshelf indefinitely!