Circadian rhythms and shift work – the ultimate guide

Circadian rhythms and shift work is such an important topic, but sadly very few quality resources exist on how to manage shift work best. Hence it is time to present a comprehensive guide on how to tackle shift work from a circadian perspective.

Shift work (aka a changing schedule) is the very definition of circadian disruption. Changing your rhythms throws off your body’s timetable. It takes longer than you imagine for your body to adjust to a disruption in your circadian rhythm. For example, one night of shift work can reduce your cognitive capabilities for a week. But the recovery of cognitive functioning after having left long-term shift work takes a minimum of 5 years [1].

Shift workers are generally defined as employees who stay awake for more than three hours between 10 pm and 5 am for more than 50 days a year. But basically, any activity that disturbs your regular sleep and eating schedule will cause circadian disruption

The are various types of “shift work” you can participate in. Are you a classic shift worker required to work into the night like firefighters, police, health workers, caregivers, restaurant staff, and many more? Are you a frequent traveller crossing time zones? Are you a student, mother, caregiver, or musician that often burns the midnight oil? Are you sleeping in on the weekends? If you answered yes to any of the above, you could consider yourself a shift worker.  

For most people, adjusting to a shift of one hour takes an entire day (think travelling across time zones, daylight savings time or sleeping in). This not only affects sleep. Essentially any organ and function can be compromised by a disrupted circadian rhythm.

Of course, the greater the difference in the rhythm, the worse it is and the longer it takes for the body to adjust. Night shift work can be brutal as it requires you to turn your biology on its head, be active and alert at night and sleep during the day.

The health risks of being a shift worker have been known for decades. They range from fatigue to sleep disorders, mood disorders, gut issues, cancer, heart disease, obesity, diabetes and more.

But what can you do to mitigate the risk of being a shift worker? As shift work moves you out of sync with your environment, you want to adjust your behaviour accordingly. Your circadian rhythm and shift work need to be aligned as best as possible. For night shift workers, that means doing everything inverse. You need to think about the main circadian cues: light, food and activity. 

In a nutshell, you need, 

  • natural light when you wake (and during your active phase),
  • darkness leading up to and during sleep, 
  • to eat early and stop eating well before bedtime,
  • and be physically active after waking and move frequently. 

The above is the general framework for an ideal circadian day. Shift workers want to play by the same rules as much as possible to mitigate the impact of being active in a different “timezone”. Yes, you operate on a different artificial schedule, but you want to behave and act as if that is not the case. You need emphasised circadian cues to enable your biology to adjust as best as possible. Here is a detailed rundown of things you can do: 


1. Keep the same rhythm

day night active rest periodIn other words, minimise the flux! Alternating shifts is the worst possible scenario; you want to do whatever you can to avoid this. Why? Because by the time your new shift comes around, your body might not have caught up to the last change, and now you are on a new schedule altogether. In this scenario, you really cannot win.

If you cannot get out of alternating shifts, aim to space out the changes as far apart as possible (ie. every ten days instead of every three days). Further, minimise the schedule change in terms of hours (ie. it is better to go from an afternoon shift starting at 3pm to an evening shift starting at say 7pm, instead of going from 3pm to 10pm). It is also easier for the body to adjust to a forward-moving schedule rotation instead of a backwards-moving one. 

If you work a particular shift most of the time (say 22 days out of 30), keep the same rhythm on your off days. Do not try to get back to a normal rhythm on your non-shift days, as this is too much in terms of adjustment and will only undermine the functioning of your entire biology.

Similarly, if you only work a few night shifts here and there (say 6 days out of 30), switch back to your regular rhythm after the shift. This is far from ideal, but generally, a better option as you can participate in normal social life and be in sync with your local light/dark environment most of the time.

Maintaining the same rhythm as much as possible is the best possible foundation you can give yourself. If you manage your circadian rhythms and shift work in a way that allows for the same sleep and wake times, you are truly taking ownership of your health.


2. Bright light exposure after waking and during your wake period

Wake up well before you need to show up for your work/shift. You first want to get a big dose of unfiltered natural light in your eyes – the longer, the better, but give yourself at least 10min. Do this independent of the time of day (morning, midday, afternoon or evening). You need to wake up and sync your master clock to your shift schedule. For this, you need bright natural light. If natural light is unavailable, you want to use a full spectrum light box and get your light dose that way.

You also want to be exposed to lots of balanced light during your shift. This is where you are very limited in terms of mitigation, as natural light will likely be unavailable for you. If you can control the light environment you work in, use a circadian-friendly light or a full spectrum light box. If you have no influence over the artificial lighting conditions at work, consider adding a red light device to your work environment and/or wearing daytime blue blockers. These are usually yellow lenses that reduce the unnaturally high content of blue wavelengths of modern LEDs by about 50%.

You need sufficient light into your eyes to trigger cortisol release from your pituitary gland and suppress melatonin release from your pineal gland. But since the spectrum of most artificial light sources is very unbalanced, you want to mitigate the altered light spectrum for the sake of your eye and adrenal health.


3. Exercise after waking

After waking, you also want to move physically and perhaps do a workout routine. As movement entrains the circadian clocks in your muscles, this gives you a second circadian cue, tells your body that the “day” started and aligns with the light cue that your master clock received.

Movement kickstarts your overall circulation, wakes up your body and makes you feel good. Combined with a good dose of natural light to your eyes, you are winning already.


4. Cold exposure after waking 

If you want an extra lift and kick to start your “day” on a high, get cold. Even just finishing a warm shower with a minute or two of cold water at the end will be a game changer. If you want to amp it up, have your shower only cold or go all out with an ice bath. Obviously, build up to that over time and make sure you focus on slow deep breaths when befriending the cold. 

The boost in mood and aliveness from a short burst of cold stress is second to none. It will also make you much more resilient over time in terms of stress and susceptibility to diseases. And, of course, you will be wide awake after a dose of cold, more than any cup of coffee ever could.


5. Have a proper breakfast

When you eat, you kickstart your entire metabolic system, entrain your digestive clock genes, and change your hormones. You metabolise foods most efficiently a little while after waking. Hunger rises, satiety is at its lowest level, and you are most insulin-sensitive if your biological rhythms are healthy and entrained reliably. Eating a substantial and hearty breakfast aligns with your metabolism and locks in your circadian rhythm by setting your digestive clock genes. Ideally, wait one hour after you wake, but eat within 3 hours of rising to closely align the clocks in your gut with the master clock in your brain.

If you only work shifts a few days a month, you might want to consider fasting on those days or only having breakfast. This way, the clock genes in your gut and liver do not get varying time cues compared to your regular days.   


6. Exercise instead of caffeine/stimulants

Restrict coffee/caffeine and other stimulants to the first half of your waking period. If you need a lift after that, a short bout of exercise will serve you much better than a cup of coffee. Move your body, get your heart pumping, and use your muscles.

When you feel the drag of being awake during the natural rest period, take a few minutes and get active. Jumping jacks, running on the spot, squats, push-ups, or whatever is doable and appeals will do the trick. Make a short movement spell your new habit whenever you need to be more alert. Let yourself be surprised by what happens.


7. Blue Blockers a few hours before bed

circadian rhythm and shift work dragDepending on your level of wakefulness/alertness, you want to start using evening/nighttime blue light-blocking glasses a few hours before you go to bed. The best circadian practice would be to use orange lenses (block all blue and some of the green spectrum) while you are still at work and switch to red lenses (block all blue and most or all of the green wavelength) when you head home. Of course, you need to be safe at work and while driving. Hence it is your call to decide whether this is possible for you or not. 

If blue blockers are not an option, at least use sunglasses. Sunglasses do reduce across the entire light spectrum. This is not ideal, but you need to minimise the amount and brightness of light that reaches your eyes. Especially blue light needs to be removed as much as possible (hence blue blockers) as this is an on-switch for your pituitary gland and suppresses melatonin release from your pineal gland. 

Without eliminating blue wavelength, you inhibit your biology from preparing for and switching to rest and digest mode. This is a huge issue if you are on a normal sleep/wake rhythm. But if you are working on an arbitrary schedule, you need even stronger circadian cues to solidify the inverse rhythm you are on. Check out these 3-in-1 blue blockers from VivaRays to give you the necessary flexibility. Discount codes are on our product page.


8. Stop eating 3-4 hrs before your bedtime

Every time you eat, the process of digestion, absorption, and metabolism takes a few hours to complete. Increasing the time between your last meal and your bedtime will improve your sleep, cellular repair, and the amount of fat you burn. As eating is a circadian cue, you want to leave at least 3-4 hrs between your last meal/snack/calorie and bedtime.

Cellular repair and regeneration can only happen if your body isn’t busy with other tasks. Make it easy for your body to support you with better sleep, metabolism, hormonal balance and renewed cells by stopping eating well before bedtime.


9. Pitch black bedroom

You are likely to sleep partially during daylight hours as a shift worker. Any light reaching your eyes will interrupt your sleep and circadian rhythm. Even your skin has photoreceptors that will respond to a light stimulus. Hence best practice would be to use a blackout eye mask and blackout curtains. This way, both your eyes and skin are protected. Darkness is a necessity to optimise your biology.


10. Turn off phones, doorbell, wifi etc

To further support your rest period during the active phase of the world, you want to take a few further steps to create the best possible sleep for you.

Eliminate any sounds that can disturb you. Turn off any phones, beepers and watches. Turn off the doorbell and/or put a do not disturb sign on the front door. Depending on how light a sleeper you are and how noisy your immediate environment is, you might also want to use earplugs.

You are an electromagnetic being, and your mitochondria are finely tuned environmental sensors. Electromagnetic frequencies (EMFs) from modern technology and appliances will interfere with many aspects of your biology. This is why you want to minimise your level of EMF exposure, especially while you sleep. Hence turn off any electronic devices in your house and unplug any devices in your bedroom.


11. A last resort – supplementing melatonin

This is only mentioned as a last resort if you still struggle to get good sleep after implementing all the other strategies. Taking exogenous melatonin is very popular, but it is only a band-aid that comes with various side effects and consequences. 

Just consider what happens when melatonin is released from the pineal gland in your brain. The melatonin concentrations in the brain are very high and low in the bloodstream. This is the inverse when you take a melatonin pill. Not a smart move.

One of the most common side effects of supplementing melatonin is daytime grogginess, as the levels in the blood are likely still elevated.

All this being said, if you feel like you have to use a temporary crutch to get better sleep, supplementing melatonin can be very supportive in the short term. But please use it as a means to an end while implementing all the other strategies. Your body knows and does best if you support it with the right choices and behaviours. 

If you only work shifts one or two days a week, you could use melatonin to pivot your rhythm on these days.


12. A support tool to manage circadian rhythms and shift work better

circadian rhythm and shift work circadian app dashboard afternoon wake upSet your new rhythm and live by it every day. Our mobile app “Circadian: Your Natural Rhythm” is designed to give you the details of WHY and HOW. Even though Circadian it is not designed for shift workers, you can still hugely benefit from greater overall rhythmicity and consistency. In the screenshot, you can see an example of the sleep period falling into daytime and hence how the eating, exercise and cognition rhythms are shifted. If you are a shift worker and are using Circadian, let us know what would help you to get even more value from the app. Here is to better health and vitality for everyone. Start applying the science of circadian rhythms to shift work. We are keen to hear how it impacts you! You can always email us at

A note on references: this guide on circadian rhythms and shift work does not contain references pertaining to the best management practices. Why? Because all of those (over 1000 thousand) are in our app “Circadian: Your Natural Rhythm“. As you understand by now, most of us are “shift workers” to varying degrees. All guidance referring to an ideal circadian day aligned with the natural light and dark cycle apply to any shift work as well. It is just much harder, more limited and challenging to live by an inverse or “shifted” rhythm. But if you want the scientific resources backing all the above recommendations, jump in the app and be ready to dive deep.


To summarise:

Minimise the flux and changes in your rhythm. Aim to live an ideal circadian day, whether your active/rest phase is in line with nature or not. In the long term, you want to look at options to live, work and sleep in sync with the natural light and dark cycles. No amount of mitigation will prevent negative health consequences from long-term shift work and defying nature. After all, you are a diurnal mammal, not a nocturnal one.




Here are some results from recent studies on the health effects of disrupting circadian rhythms and shift work:

Shift-working women have several gender-specific health concerns and may be especially at risk for developing menstrual cycle irregularities, problems with reproductive health, and breast cancer. [2]

Shift work increases myocardial infarction reperfusion injury [3].

Night shift workers had a higher hypertension risk than day shift workers [4].

Frequent shift work increases the risk for Non-Alcoholic Fatty Liver Disease [5].

Shift work and sleep duration are both associated with adverse pregnancy outcomes [6].

Shift workers have lower levels of vitamin D compared with non-shift workers [7].

NTP study from 2021 shows that shift work is officially a carcinogen [8].

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