Circadian Rhythm Test: This App Can Predict It

Whether you’re looking to get more energy or fall asleep faster come bedtime, your circadian rhythm (or body clock) plays a part. When you work with it, everything from your energy to your sleep, your productivity to your mental and physical health are boosted. 

But knowing the timing of your circadian rhythm isn’t exactly intuitive. Luckily, there are some tests you can do to find the timing of your circadian rhythm, so you can get the most out of it. 

Below, we’ll dive into what your circadian rhythm is and how you can use the RISE app to test for it and improve your health, well-being, sleep, and energy. 

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Advice From a Sleep Doctor

“My key piece of advice for keeping your circadian rhythm in check is to think about light," says Dr. Chester Wu. "Try to get out in natural sunlight each morning and make your nights as dark as possible. This will signal to your circadian rhythm when it’s time to be awake, and when it’s time to sleep.”

Dr. Chester Wu is double board certified in Psychiatry and Sleep Medicine, and provides sleep medicine services, medication management, and psychotherapy to adults at his private sleep medicine and psychiatry practice.

While you’re sleeping, working, and living your life, there’s a biological clock ticking away inside of you. This is your circadian rhythm. 

This internal clock runs on a roughly 24-hour cycle and dictates your sleep-wake cycle, the production of certain hormones, and body temperature and blood pressure fluctuations, amongst many other things. 

But there’s more than one circadian clock to think about. We all have one master clock in our brains. This is called the suprachiasmatic nucleus (SCN). It’s found in a part of the brain called the hypothalamus and it runs the show as the central pacemaker. 

Beyond the SCN, there are clocks in almost every tissue and organ system in your body — including in your gut, immune system, and liver. These are called peripheral clocks.

The SCN is attuned to the light-dark cycle of the outside world, and it communicates with peripheral clocks around your body. All of these circadian rhythms work together to tell your body the best time to eat, sleep, be alert, and so on. 

Your circadian rhythm isn’t set in stone, though. It receives signals from the outside world — also known as zeitgebers (German for time givers) — which act as a cue telling your clock what time it is. 

Zeitgebers include: 

• Light (the most powerful cue)
• Eating
• Exercising

When you get light exposure, eat, or exercise, you can either reinforce your circadian rhythm (i.e. confirm it’s running at the right time) or you can make it shift earlier or later. 

This process is called entrainment, which simply means the setting or resetting of your circadian rhythm. 

Another key term to be aware of is the phase-response curve (PRC). This is the relationship between a zeitgeber and the response it causes. In simple terms, there’s a time of day when a zeitgeber switches from shifting your circadian rhythm earlier to pushing it back. 

For example, when you get morning sunlight, you’re telling your circadian rhythm it’s daytime and time to be awake and alert. When you get bright light in the evening, however, you can push back your circadian rhythm, making it harder to fall asleep. 

Your circadian rhythms can run out of sync with your day-to-day activities, too. When you’re living out of sync — perhaps by sleeping at irregular times or working night shifts — you can experience poor sleep, low energy, and an increased risk of everything from obesity to depression, heart disease to cancer.

Chronotypes and Your Circadian Rhythm 

You could probably make a good guess at whether you’re more of an early bird or night owl. These are chronotypes, or a natural tendency to go to sleep, wake up, and be alert earlier or later in the day. 

If you’re an early chronotype (also known as morning type, early bird, or lark), your circadian rhythm will skew earlier. Everything — including your sleep-wake cycle — will happen earlier in the 24-hour cycle. 

If you’re an evening chronotype (also known as evening type or night owl) it’s the opposite. Your circadian rhythm will skew later, and your sleep-wake cycle will be later in the 24-hour cycle. 

While your chronotype is determined by factors like age and genetics, you can still shift the timing of your circadian rhythm. For example, one study found when night owls were exposed to natural light only for a full week — no artificial light or screens — their circadian rhythms shifted earlier in the day to look more like those of early birds. 

Research suggests about 40% of us are either morning or evening chronotypes, while the rest of the population sits somewhere in between. Not sure where you sit? We’ve covered how to find out your chronotype here. 

What Other Rhythms Are There? 

It may sound complicated, but there are natural rhythms in other areas of life: 

• Circadian rhythms: These are roughly 24-hour rhythms like the sleep-wake cycle or body temperature fluctuations. 
• Diurnal rhythms: These are rhythms that are synced with the day-night cycle. 
• Ultradian rhythms: These are shorter rhythms, like the cycle of sleep stages between rapid-eye-movement (REM) and non-rapid-eye-movement (NREM), or the rise and fall in energy and productivity you get over about 90 minutes. 
• Infradian rhythms: These are cycles that are longer than 24 hours like the monthly menstrual cycle

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Why Should I Do a Circadian Rhythm Test?

Apart from being a fun experiment, there are many benefits to doing a circadian rhythm test. 

Here’s what you can do when you know your circadian timing: 

• You can find out when your body naturally wants to go to sleep and wake up: When you know this, you can sync up your sleep-wake cycle and have an easier time falling asleep and getting enough sleep at night. By meeting your sleep need (the genetically determined amount of sleep you need) you’ll have more energy (not to mention better health, focus, and mood) each day. 
• You can find when you’ll naturally have more energy in the day: Then, you can schedule your most important work and demanding tasks during this time, making you more productive. You can learn how to use RISE as a personal energy tracker here.
• You can sync up with your circadian rhythm overall: By sleeping and eating when your body wants you to, you can reduce your risk of health issues like weight gain, digestive issues including IBS, diabetes, depression, and even ADHD. New research is coming out on the health risks of circadian misalignment all the time. For example, research from 2023 states disrupted circadian rhythms from ill-timed food and light exposure can mess up your hormones and metabolism. 
• It’s useful for chronotherapy: Chronotherapy looks at delivering medication at the right time for your circadian rhythm to make it more effective and have fewer side effects. For example, we’ve covered the best time to get a flu shot and COVID shot here. Spoiler: Morning vaccinations are better for flu shots, while 10 a.m. to 2 p.m. may be the best time to get a COVID vaccine.  

Beyond your circadian rhythm, RISE can work out your unique sleep need, so you know what you should be aiming for each night. 

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Want to find out the timing of your circadian rhythm? There are a few ways you can test for it. 

Keep a Sleep Log 

One way to test for your circadian rhythm is to keep a sleep and energy log for a minimum of seven days, ideally 14 days. 

Clinicians often use sleep logs to diagnose circadian rhythm sleep-wake disorders (CRSWD). But you can use this method yourself at home. 

Try going a week or two without an alarm and make a note of your natural sleep and wake times. Then, during the day, make a note of when you feel most alert and focused, and when you feel your energy is lower. 

This method can give you an idea of your chronotype and the rough timings of your circadian rhythm. 

But there are a few problems with this method, including: 

• It’s hard to go a whole week — let alone two — without an alarm.
• It’s hard to know if you’re going to bed later because you’re a night owl with a later-running circadian rhythm, or if something like pre-bed screen time or too much coffee is keeping you awake.  
• It can be inaccurate — it’s hard to tell when exactly you fall asleep each night. 
• It doesn’t give you much information — you might find out your rough natural sleep times and energy highs, but that’s about it. 
• Your circadian rhythm can change — so finding it out just once isn’t that useful. To really make the most of it, you want to know your circadian rhythm each day, and be one step ahead of it, so you can plan your days and nights to match.

Take an Online Quiz or Survey 

There are plenty of online quizzes and surveys out there promising to tell you the timing of your circadian rhythm in just a few clicks.  

This method is similar to keeping your own sleep log. You’ll probably be asked about your sleep times, when you feel most alert, and the times you do certain activities on your days off. 

There are also more official surveys that are often used in scientific research. These include: 

• The Munich Chronotype Questionnaire: This survey uses your sleep midpoint to work out your chronotype. Your sleep midpoint is the middle of your sleep times. So, if you sleep from midnight to 8 a.m., your sleep midpoint would be 4 a.m. 
• The Morningness-Eveningness Questionnaire: This survey asks you questions about when you prefer to sleep, exercise, and eat your meals. You’ll then get a score for where you sit on the scale of morning type to evening type. 

These questionnaires and online quizzes don’t measure circadian rhythms exactly, but they can give you an indication of whether yours naturally skews earlier or later.

These methods have many of the same problems that keeping your own sleep log does, including: 

• It relies on self-reported data, which can be inaccurate.
• Again, it’s hard to tell if things like coffee or screen time are keeping you awake, or if you’re a night owl. 
• You don’t get much practical information to work with, just whether you’re more of a morning or evening person. 

Get Tested in a Lab

You can check into a lab and get scientific measurements of your circadian rhythm. This method involves checking for markers of your circadian rhythm such as your: 

• Core body temperature
• Melatonin levels
• Cortisol levels
• Sleep times via a polysomnographic recording, which records brain waves, heart rate, and breathing 
• Activity levels via a wearable device 
• Dim light melatonin onset (DLMO) — which is the moment melatonin starts to be produced, usually about two hours or so before your biological bedtime. 

There’s also a blood test that can measure your circadian rhythm from biomarkers from a blood draw, but this isn’t widely available yet.

There are a few problems with getting a circadian rhythm test in a lab, too. 

• It’s expensive and lab visits aren’t often covered by insurance.
• It can be time-consuming. 
• It can be unreliable as self-reported data is sometimes used, like sleep logs or activity diaries.
• To measure melatonin in your blood, several blood samples may be needed, which isn’t ideal or always done.
• It’s not practical — who can realistically visit a lab every time they want to check in on their circadian rhythm? 

Use the RISE App 

Most of us can’t (or simply don’t want to) check into a lab, and surveys and online quizzes aren’t a reliable way of testing your circadian rhythm. This is where the RISE app comes in as a test for your circadian rhythm. 

It’s quick, easy, reliable, and you’ll get practical information you can use to improve your sleep, energy levels, and overall wellness. No blood draws needed, just a smartphone. 

Another plus? You’ll also be one step ahead of your circadian rhythm as you’ll see a prediction of what it’ll look like each day. This will help you plan your day effectively and stay in sync to boost your energy levels, sleep, and productivity (more on how to do all that soon). 

How Does RISE Work? 

RISE uses your inferred light exposure, recent sleep times, and science-backed algorithms to predict the timing of your circadian rhythm. 

Our prediction model is built on the SAFTE model (which stands for sleep activity, fatigue, and task effectiveness). This model was developed by the US Department of Transportation and the Department of Defense, and it predicts changes in cognitive performance based on your circadian rhythm.   

RISE does all the complicated science in the background, but you’ll get a simple visual of your circadian rhythm. You’ll see how your energy fluctuates over the day, including when your body wants to wake up, wind down for bed, and sleep.

Speaking of sleep, RISE also shows you your Melatonin Window. This is what we call the roughly one-hour window of time when your body’s rate of melatonin is at its highest. Melatonin is the hormone that primes your body for sleep, so your Melatonin Window is essentially your ideal biological bedtime. If you go to bed during this one-hour window, you should find it easier to fall and stay asleep. 

How do we work out this window? We use the St Hilaire mathematical model of core body temperature, inferred light exposure, and sleep times to calculate your DLMO. Then, we add 1.55 hours to this — as research suggests the ideal bedtime is about two hours after your DLMO — and add and subtract 30 minutes from this time to get your ideal one-hour bedtime window. 

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Your circadian rhythm is constantly running in the background of your life, but you can get out of sync with it (also known as circadian misalignment). 

You might be out of sync with your circadian rhythm if: 

• You work night shifts or rotating shifts. 
• You have social jetlag, or you go to sleep later on your days off compared to work days. 
• You’re living at odds with your chronotype — perhaps you’re a night owl who has an early work schedule.

When your circadian rhythm is disrupted, you may find it harder to fall asleep at night, struggle with daytime sleepiness, have lower focus during the day, and you’ll be damaging your health, too. 

You can reset your circadian rhythm, though, shifting it to suit the timings of your daily life. Here’s how:

• Shift your wake and bedtimes gradually: Try moving your sleep times 15 to 30 minutes earlier or later, depending on which way you want to shift your circadian rhythm. 
• Shift your meal and exercise times: Do this by the same amount in the same direction as your sleep cycle. 
• Get bright light first thing: This tells your circadian rhythm what time it is, setting it to the outside world. 
• Avoid bright light before bed: This will give you a better chance of falling asleep at your desired bedtime. Light in the evenings can push back your circadian rhythm and keep you awake. 
• Take a melatonin supplement: As a last resort, you can take melatonin supplements to shift your sleep schedule.

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Your circadian rhythm can get thrown off by your sleep or work times, but a disorder may also be to blame. Some of these disorders are caused by your sleep and work, too. 

Circadian rhythm disorders include: 

• Delayed sleep-wake phase disorder: When your sleep is abnormally delayed compared to the light-dark cycle of the outside world and it’s causing chronic and severe sleep loss. 
• Advanced sleep-wake phase disorder: When your sleep is abnormally advanced compared to the light-dark cycle and it’s causing chronic and severe sleep loss. 
• Shift work sleep disorder: When shift work has disrupted your circadian rhythm, leaving you sleepy at work and alert when you need to sleep. 
• Jet lag disorder: When you travel across time zones and your body clocks take a while to adjust.
• Non-24-hour sleep-wake disorder: This disorder primarily affects blind people who can’t signal to their SCN with light. Their sleep cycle may gradually shift later over time as they can’t reset it. 
• Irregular sleep-wake rhythm disorder: This disorder causes you to have no pattern in your sleep schedule. Instead, you may take several naps over a 24-hour period. This disorder is often seen in those with Alzheimer’s or a brain injury. 

Speak to a doctor if you think you have a circadian rhythm disorder. They may be able to recommend behavioral changes and treatment options, like melatonin supplements and light therapy.

How to Maintain a Healthy Circadian Rhythm

Once you know your circadian rhythm, and have perhaps reset it to suit your lifestyle, it’s time to keep it on track. This will ensure you’re taking the best care of your health, and it’ll help you enjoy better sleep and more energy. 

Here’s what to do: 

• Keep a consistent sleep pattern: Find a sleep schedule that works for you and stick to it, even on your days off. 
• Get light in the morning: This will signal to your circadian rhythm what time it is, keeping it running on schedule. Aim for at least 10 minutes of light as soon as possible after waking up and if it's overcast or you’re getting light through a window, make it 15 to 20 minutes. 
• Get light during the day: The more light exposure you get during the day, the less sensitive you’ll be to evening light. Try working by a window, going for a walk on your lunch break, and taking your workout outside. 
• Avoid light in the evenings: About 90 minutes before bed, dim the lights and put on blue-light blocking glasses (we recommend these).
• Eat meals at roughly the same times and during the day: Eating may not be as powerful as light, but it can still change the timing of your circadian rhythm, and eating too close to bedtime can keep you up. 
• Go to bed during your Melatonin Window: Check your Melatonin Window each day, or get a reminder when it’s coming up, and aim to head to bed within this one-hour window. 
• Maintain good sleep hygiene: These are the behaviors you can do to help you fall and stay asleep at night, and therefore stay in sync with your ideal sleep-wake schedule. Good sleep hygiene includes getting light exposure first thing and avoiding light, caffeine, and large meals too late in the day. RISE can guide you through 20+ healthy sleep hygiene habits each day and tell you when to do them based on your circadian rhythm to make them more effective. 
• Make the most of your energy peaks and dips: This tip will help you make the most of your circadian rhythm. Schedule hard tasks for when you feel your most alert (usually the morning and early evening) and easier tasks or breaks for when your energy naturally dips in the afternoon.  

For a final piece of advice, we turned to Dr. Chester Wu, who is double board certified in Psychiatry and Sleep Medicine. Here’s what he had to say about how best to keep your circadian rhythm in check. 

“My key piece of advice for keeping your circadian rhythm in check is to think about light. Try to get out in natural sunlight each morning and make your nights as dark as possible. This will signal to your circadian rhythm when it’s time to be awake, and when it’s time to sleep.”