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Can you have a biphasic temperature chart and not ovulate?

Can you have a biphasic temperature chart and not ovulate?

Catherine Poslusny | August 5, 2020 | Fertility Awareness

Learning how to chart your menstrual cycles is one of the best ways to demystify your body’s complex reproductive processes and take charge of your fertility. The more you know about tracking your fertility signs, such as basal body temperature (BBT) and cervical mucus, the better you can predict when you’re fertile. This knowledge can be incredibly empowering, but it can also be difficult to come by. (That’s why this blog is so important!) 

Charting your BBT can be especially tricky because you need to follow fairly strict guidelines to get accurate measurements. Even then, interpreting your BBT chart can be a challenge. In this post, we’ll break down exactly what people mean when they refer to a “biphasic chart” and whether that’s a reliable indicator that you’re ovulating regularly.

Why does BBT spike after ovulation?

Your basal body temperature is your temperature when your body is at rest, and tracking it throughout your menstrual cycles can be an inexpensive way to gauge when your fertile days are over for the cycle and to confirm that you have ovulated. But before we get into charting your BBT, let’s first touch on how it relates to ovulation. When you ovulate, an egg is released from a mature follicle in your ovary. Once empty, the follicle (now called a corpus luteum) starts secreting progesterone. This usually causes your temperature to rise by about 0.5-1 degree Fahrenheit and remain raised until the end of your menstrual cycle (1, 2).

A sustained (3 days or more) rise in your BBT is a pretty good indicator that you’ve ovulated. It’s important to note that BBT tracking requires a commitment to taking your temperature at the same time every morning, before you do anything, and after you’ve gotten at least 3 consecutive hours of sleep. If you don’t stick to the routine, your results won’t be as reliable (1, 3). 

Another important note about BBT: It only tells you that you’ve ovulated after it happens. If you’re looking for a way to predict ovulation before it happens, check out our post on continuous core body temperature, circadian rhythms, and fertility

What is a biphasic chart?

Once you’ve been recording your daily BBT for two or more complete cycles, you may start to see a pattern emerge. If you’re ovulating regularly each cycle, you should notice that your temperature falls into two ranges — a lower range that occurs during the first part of your cycle, before you ovulate, and a higher range that lasts from the day after you ovulate until you start your period. If you see these two distinct phases in your BBT measurements, it means you have a biphasic chart (1).

Pro tip: It’s easier to see your BBT patterns when you plot your daily temperatures for each cycle on a graph (either using plain graph paper, a specific BBT-tracking chart, or a fertility app) with the days on the horizontal axis and your temperature on the vertical axis. You can find more information about BBT in our blog post, Basal Body Temperature 101.

Can you have a biphasic chart and not ovulate?

Probably not. When BBT readings consistently stay within one range during the first part of your cycle, and they move to a different, slightly higher range for the rest of your cycle, that’s a sign of regular ovulation. It’s normal for your temperature to fluctuate from day to day, but it’s highly unlikely that you’ll have a true biphasic chart cycle after cycle if you’re anovulatory. Of course, this is assuming that you’re recording your BBT at the same time every morning and there aren’t any outside factors affecting your measurements (4). 

These environmental factors that influence temperature are exactly why we included a way to mark questionable temps in our Kindara App. 

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Can you ovulate without a biphasic chart?

It is possible to ovulate without a biphasic BBT chart. Sometimes temperature shifts after ovulation may be too small to recognize on your chart, or your temperatures may not fit into a strictly biphasic or monophasic pattern. So if you’re not seeing a biphasic pattern in your charts, that doesn’t necessarily mean you aren’t ovulating, but it’s a good reason to check in with your doctor (3). Fortunately, BBT is only one of a few signs of ovulation that can help you figure out when you’re fertile (4).

Other factors that can influence your BBT 

Though it’s highly unlikely to have a biphasic chart during anovulatory cycles, that doesn’t mean that ovulation is the only thing that can impact your BBT. First of all, how you take your basal body temperature can affect your readings. For example, if you don’t take your temperature at the same time every morning, or if you don’t get a good night’s sleep the night before, that can skew your BBT readings (4, 5).

Even if you have a consistent sleep schedule and never have trouble sleeping through the night, there are still other factors that can influence your BBT measurements. For example, getting sick, drinking alcohol, traveling, holidays, shift work, and even stress can all potentially alter your morning BBT (6, 7).

What should you look for in a biphasic chart?

If your BBT can rise for reasons that have nothing to do with ovulation, how can you be sure that your chart is biphasic? The first step is to look for patterns in your measured temperatures that are consistent from cycle to cycle. These changes are less likely to be caused by one-off events, like that time you had to get up to pee an hour before your alarm went off or that weekend that you had a cold. Next, look at your temperature in the days following the initial rise. If your BBT stays in the higher range for at least three days, it’s a good sign that you’ve ovulated (3).

If you have a consistently biphasic chart, it’s highly unlikely that you’re not ovulating. However, ovulation isn’t the only factor that can cause changes in your BBT, and it’s not always easy to tell whether you’re actually seeing two distinct phases in your chart. Tracking other fertility signs can sometimes help clear things up. You can also talk to your doctor about testing to confirm ovulation. If, on the other hand, you’re confident that your chart is biphasic, you can use it as a reliable tool to confirm that you’ve ovulated.