An Introduction to Body Temperature
In this article, we cover all things related to your body temperature. If you’re curious about how Oura measures body temperature, why fluctuations are worth keeping track of, or how to interpret changes using the Daily and Trend views in your Oura app, you’ve come to the right place.
How Oura Measures Body Temperature
Temperature is one of your core vital signs and a key indicator of your body’s status. Oura measures your body temperature every minute, directly from the skin of your finger—in this way, Oura is able to capture a full picture of changes in your body. Most wearables don’t measure body temperature and when they do, many use outward-facing sensors to gauge your temperature based on the external environment or estimate it based on your heart rate. Additionally, wrist oriented wearables are heavier and more likely to move, thereby exposing them to surrounding temperature. The ring in comparison, has a minimal profile and can nimbly follow temperature changes as its NTC (negative temperature coefficient) temperature sensor is always in close contact with the skin.
Keep in mind: the Oura app leverages insights from your average nighttime temperature. This is because, at night, your body is in its most stable state. During the day, your body temperature is subject to constant changes in your environment and the choices you make (e.g. consuming food and beverages or going on a walk outdoors), which can confound your data with excess “noise”. Considering this, nighttime is the best opportunity to get an accurate representation of your body’s true current state and overall well-being.
In the Oura app, your daily body temperature appears on your Readiness tab and answers the question, “How much higher or lower is my body temperature today compared to previous days and weeks?”
This value represents how much your body temperature from your most recent night’s sleep changed, either in a positive or negative direction, from your long-term average (e.g., it’s +0.3° or -0.2° today compared to your normal body temperature).
Your body temperature can also be viewed by accessing Trends , which is located in the menu in the upper left-hand corner of your Home tab. Upon opening Trends, you'll see a 'Temperature' quadrant displayed in the mid-left of the screen. Here, you'll see your nightly body temperature deviation from your long-term average, displayed in large font. You'll see a small Trend arrow to the right of this value, which indicates if your body temperature has increased or decreased from the previous day. You'll also be given a rating (pay attention, good or optimal), which matches the body temperature contributor score found in your Readiness tab.
Tap on the arrow in the upper right-hand corner of the Temperature quadrant to get a visualized and more detailed view into your daily body temperature fluctuations over time. More information on how to interpret and understand these changes can be found below.
Interpret Your Body Temperature
We advise Oura users to keep an eye out for any fluctuation greater than 0.5°C / 0.90 °F, in either a positive or negative direction. Any change greater than this may be an indication that something is challenging your system—which is why we recommend paying attention to these circumstances. Tune into your body if you notice anything outside of your personal norm and take the time for additional rest and self-care if you feel it necessary.
More specifically, temperature can be used to identify strain and recovery, emerging illness, and phases of the menstrual cycle. You'll discover more on each of these elements below.
1. If you’re training, body temperature can help you spot signs of strain and recovery. If you’re pushing your body, you’re likely to see slightly elevated temperatures as your body works harder than usual to repair through its natural recovery process. Once your temperature returns to your baseline, it’s a sign of recovery.
2. If you’re feeling under the weather, body temperature can help you monitor yourself for illness. Elevations in your body temperature, alongside other symptoms of illness such as headache, fatigue, congestion, or sore throat are likely a sign that your body has turned on regulatory processes, such as fever, that are related to the stimulation of your body’s immune response.
Keep in mind that increases in your body temperature due to illness may also cause changes in other metrics visible in your Oura data, such as:
• Increases in respiratory rate that are ~2 breaths per minute above your normal average.
• Increases in your resting heart rate and, or decreases in your heart rate variability as your body engages your sympathetic (“fight-or-flight”) nervous system while trying to ward off various elements of sickness such as bacteria, viruses, etc.
• An extension of the amount of time spent in deep sleep, the most physically restorative sleep stage—which tends to occur alongside a time of needed recovery.
Be sure to stay attentive to these relational changes if you notice a spike in body temperature and are looking to gauge other, emerging signs of illness.
3. If you’re tracking menstrual cycle patterns, you can also use variations in body temperature to understand which phase of the menstrual cycle you’re in. Specifics will be covered in more detail in the section at the bottom of this article, but the primary benefit here is rooted in awareness.
Oura is not meant for fertility tracking, but understanding where you are in your cycle can have major lifestyle benefits, as each phase is associated with different hormonal changes. Knowing how one’s body may feel or respond at certain times of the month is an empowerment tool for all individuals who currently undergo menstruation, so they can act accordingly based on their personal needs.
Keep in mind:
• Your body temperature metric is slightly different from other metrics found in your Oura app because it only contributes to your Scores when body temperature is abnormal. This means body temperature can only lower your Readiness Score, not boost it. If you notice significant spikes clearly outside of your normal range (e.g. due to illness), you'll see a lowered Readiness Score.
• If you notice changes in skin temperature that are lower than your average, this is likely due to changes in your internal regulatory system, which can be due to circumstances such as low peripheral blood flow (blood flow that occurs in your arms, hands, legs, and feet), being exposed to cool environmental temperatures, or being in the follicular phase of one’s menstrual cycle.
• Oura takes into account temperature changes that occur as a result of one's natural menstrual cycle. You'll be kindly notified, instead of traditionally cautioned, of any temperature elevations relative to phases of the menstrual cycle.
Use Body Temperature Trends
You can view your body temperature trends using two different views.
To access these, simply tap on the Readiness tab and select Body Temperature in the quadrant above your Readiness Score.
The Daily view focuses on short-term temperature changes and is optimal for tracking acute reactions in the body. It displays the same value you see in your Readiness tab for each night. The Daily view is ideal for spotting when something is starting to tax your body so you can prioritize rest and recovery. This would apply in the case of monitoring for emerging illness and any type of strain on the body—may that be physical, mental, or emotional.
The Trend view is designed to help you spot trends in your temperature over time. Using the Trend view allows you to answer questions such as “What are my monthly body temperature changes like?” and, more specifically for those who menstruate, “When do I start ovulating and menstruating each month?” Each date displays a weighted average of how your body temperature varies from your baseline based on a three-day window. This means that days closer to the current date will have more of an impact on your readings.
Skin vs. Core Body Temperature
It’s important to note that Oura measures body temperature from the skin, which is not the same as basal, or core body temperature (typically estimated with an oral thermometer). While you may already be familiar with the idea that core body temperature will noticeably rise outside of its typical range when your body is under stress (e.g. due to sickness), the same is true for skin temperature. In other words, increases in core body temperature almost always coincide with increases in skin temperature, making skin temperature a reliable measurement tool for understanding how your body adapts to different circumstances. Since orally taking your temperature at regular intervals throughout the day may be inconvenient, Oura offers a non-intrusive, dependable solution for staying in-tune with your bodily changes and identifying your current state of health.
Check out The Pulse article on How Oura Measures Temperature for more insight on how your skin body temperature is a meaningful reflection of what’s happening inside your core.
Tracking Menstrual Cycles
As mentioned in the sections above, if applicable, you can use the Trend view to manage your menstrual cycle. This can be practiced by looking for body temperature changes below your baseline (the horizontal, grey-dotted line directly beneath +0.0 on your trend graph) to signal when you’re in the follicular phase (the ~14 days leading up to ovulation). In contrast, by looking for temperature changes above your baseline, you can identify when you’re in the luteal phase (the ~14 days following ovulation). Please note that if you’re currently taking hormonal birth control, these patterns may not necessarily apply to you.
• You’re likely to observe your lowest body temperature approximately one day prior to the onset of ovulation.
• During and following ovulation, body temperatures will continue to rise during the first half of the luteal phase as progesterone is released. As progesterone levels begin to decline at the halfway mark of the luteal phase, body temperature will begin to level out toward your baseline once more.
• Keep in mind that the initial spike in body temperature you observe likely represents the onset of ovulation. Although Oura is not a fertility tracking device, this may be something you want to stay attuned to, depending on what your priorities are.
Knowing when you’re approaching or currently in the luteal phase of your cycle can be relevant for those who experience premenstrual syndrome (PMS) symptoms, as they tend to occur during this phase.
Visit The Pulse to learn more about the many differences that exist between menstrual cycles, why this makes it especially necessary to tune into yours personally, and how to gain an in-depth understanding of your patterns using Oura.
The Accuracy of Oura's Temperature Data
In a study conducted by Oura's Science team, the results revealed that Oura's temperature sensor matches research-grade performance under lab conditions, remains precise in real-world conditions and reflects changes in your physiology, not your environment. Each of these findings are further broken below.
• The Oura Ring's temperature measurements matched the performance of research-standard iButtons as precisely as 0.13°C, every minute.
• 16 individuals who wore both iButtons and Oura Rings for a week were able to show that Oura continued to match the performance of iButtons (r² > 0.92) throughout their full spectrum of life events including exercising, showering, cooking, working, etc.
• In an analysis that included iButton sensors worn on the finger, as well as an 'environmental sensor' that traveled with these same 16 participants, the results revealed that while the Oura Ring and finger iButton match at 92% (r² > 0.92), temperature information from the finger is uncorrelated to the environmental temperature; 0.1% (r²=0.001).
Please check out our blog post for even more details on the study and future implications.
To learn even more about body temperature in Oura, check out this video.