Why do some people feel tired all the time?

For some people, no matter how much sleep they get, they still feel tired and low in energy. Why?

On most days, I’m a stickler for routine, especially when it comes to sleep. I get ready for bed well before I begin to feel tired: changing into my pyjamas, cleaning my teeth, and doing an overly elaborate skin care routine. I leave my phone in the dining room where it stays overnight, then retire to my bedroom – one that’s quiet, dimly-lit, and of perfect Goldilocks temperature – to scribble briefly in my gratitude journal. A half-hour of fiction reading follows, before turning the lights out at roughly 11pm. 

Eight-and-a-half hours later, my alarm rings and I wake up feeling…tired. I am early mid-life, exercise regularly, and am, as far as I know, healthy (knock on wood). Why, then, does being bright-eyed and bushy-tailed elude me most mornings, despite sufficient sleep? 

It turns out I’m far from alone. According to a 2023 meta-analysis that examined 91 studies across three continents, , ranging from to report feeling fatigued at follow-up.

When we’re stressed, our bodies produce a hormone called cortisol, which in turn raises our body temperature and heart rate to gear us up to face a threat. Cortisol levels fluctuate naturally throughout the day, but when they remain elevated, it’s harder to fall asleep and stay asleep. It’s that “tired but wired” feeling, says Whittemore.

Another really common cause of fatigue in otherwise healthy people is sleep disorders or breathing issues, says Blum.

This includes snoring, which occurs when one’s airway is partially or fully blocked. “All snoring is abnormal, and may be a sign of sleep apnoea,” he says, referring to the disorder that causes some sleepers to stop and start breathing repeatedly throughout the night.

All this can disrupt natural sleep patterns and make deep sleep elusive, says Blum. “So people get that seven to nine hours of sleep, but it’s insufficient quality.”

Dehydration is another major cause of fatigue. Other typical culprits include caffeine and alcohol. “I think most people underestimate how much they impact the quality of their sleep,” he says. “Caffeine, for instance, has a half-life of roughly five hours, which means even when you have a cup of coffee at noon, a quarter of that caffeine will remain at midnight.”

Alcohol, especially close to bedtime, can also negatively affect sleep quality in many ways: aggravating breathing problems, disrupting the circadian cycle, and blocking REM sleep. “Oftentimes you will fall asleep maybe a little faster during that first sleep cycle and get a little more deep-sleep,” explains Blum. “But after that, it just kind of bounces us around our lightest stage of sleep, causing more awakening and additional cortisol spikes overnight.”

At the end of the day, Bjørklund explains that the tips for boosting energy are mostly what our rational minds already know: “Embrace a balanced diet, address nutrient deficiencies, maintain good sleep hygiene, manage stress through techniques like mindfulness, engage in regular physical activity, ensure proper hydration, consider therapeutic interventional like cognitive behaviour therapy, and build a support network.”

Implementing those techniques, of course, is another matter entirely. It looks like a rework of my routine is in order. 

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