The basal body temperature fluctuates daily, some days more than others. Changes in behavior can cause fluctuations as well – for example, change in sleep, travel, and sickness can cause the basal body temperature to fluctuate. This can cause Natural Cycles' algorithm to take longer to understand where you are in your cycle.
The app will indicate that you have "fluctuating temperatures" if it has a hard time finding your ovulation day, due to a large spread among your temperatures. The app may warn you about a very high or low value every now and then as well, remember to take these messages seriously – it's the app trying to help you.
Under My Cycle (statistics) in your app, the app may show you that your temperature variation 'unstable' under My temperatures. Your temperature variation is the number of degrees that your temperature is likely to change within each cycle. If it shows 'unstable,' a good thing to do is to check out our guidelines on how and when to measure your temperature. Most often, it may just be a small, simple, adjustment you may need to do to improve your measurements.
If you’re working shifts
If you're working odd hour jobs, for example, if you usually work two nights per week, we recommend you to measure five days within the same time frame. Then, measure the first day after switching to daytime. Try to measure within the same time frame (+-2 hours timeframe), as soon as you wake up. Read more.
If you’re taking care of a baby
If you have a baby and need to wake up during the night often, we do recommend you to measure after your longest stretch of sleep or at least three hours of sleep. Read more.
If you travel within different time zones and/or to a different climate, add the temperature as deviating the first 1-2 days so that your body gets used to the temperature change and then measure as usual. Read more.
Do you have very few data points?
If you have a few data points (such as when you've just started with Natural Cycles) and believe that your temperature fluctuates, keep measuring until you complete one cycle of measuring and adding data. A cycle begins on the first day of menstruation and ends when your next menstruation begins, and the app will show you each cycle individually on the graph. The graph is the best place to spot a fluctuation on. You will clearly see what is a fluctuation and what is not.
Are you measuring in the right way?
Always measure before you get out of bed, as soon as you wake up. Read more.