Understanding Your Basal Body Temperature (BBT) - Progyny

Updated by the Progyny Clinical Team — June 2025.

When you’re trying to get pregnant, the more tools and information you have, the better equipped you’ll be to make a conception plan. One helpful indicator to be aware of and to chart over menstrual cycles is basal body temperature (BBT).

Why should I track my BBT?

Taken first thing in the morning, before even getting out of bed, your BBT is the lowest temperature your body reaches during rest. During the first half of your menstrual cycle, the follicular phase, your BBT will be lower. At the same time, your ovaries are preparing for ovulation by developing an egg-containing follicle. Right before the egg is released from the ovary (also called ovulation), some people experience a very slight drop in temperature. If this is the case for you, you’re going to want to have intercourse as soon as you notice this drop.

Immediately after the egg has been released from the ovary, there will be a sharp rise in temperature. This signals that you are entering the luteal phase of your cycle, or the time after ovulation has occurred. By the time you notice this temperature increase, you have already ovulated. You can increase your chances of getting pregnant by having sex during the two to three days before your temperature rises. This is usually right before you ovulate. If you’re not trying to get pregnant, avoid sex during this time or use a backup method like condoms to help prevent pregnancy.

It’s helpful to chart your BBT for several months because you’ll notice trends and get to know how your body works. That way, you know when to time intercourse for the best chance at conceiving or preventing unwanted pregnancy.

How will I know if my BBT has risen?

What you are looking for is a rise in temperature of 0.4 degrees Fahrenheit or more. If ovulation occurs, your temperature will remain higher. If your temperature remains high for more than three days, you can assume you’ve ovulated.

What if I don’t see my BBT increase?

Some people don’t experience a temperature shift during ovulation. If you don’t see a shift after a couple of months of charting, talk with your healthcare provider. Most likely, they’ll run some blood tests during your cycle or discuss other ways to determine if you’re ovulating.

What if I still don’t get pregnant?

Tracking BBT alone may not get you pregnant. Tracking your cycle over several months can help you spot patterns and figure out when you ovulate each month.

If you have irregular menstrual cycles that vary in length month-to-month, BBT charting will not be as effective. People with irregular cycles should consult with a provider to figure out why their cycles are irregular.

If you have charted your BBT for several cycles and have not achieved pregnancy or are concerned, talk to your provider. Bring your charts with you, as they will be helpful in showing ovulation trends and identifying possible problems.

If you have questions or concerns, Progyny is here for you. Please contact your Progyny Care Advocate for support.

Disclaimer: The information provided by Progyny is for educational purposes only and is not medical advice. Always consult a qualified healthcare provider for medical guidance.