What is fatigue and how is it different from sleepiness?  

People often interchangeably use the terms “feeling tired/fatigued” and “feeling sleepy”. However, for us nerds in sleep science, we like to be pedantic and differentiate being tired from being sleepy because there is use is knowing which one you are feeling. In simple terms, we think of sleepiness as “the likelihood that you could put your head on your desk and fall asleep”. For example, if you are reading this post and you’re nodding off, your eyes are feeling heavy – then you are sleepy. On the other hand, if you feel exhausted – like there’s a fog in your mind and it is hard to concentrate, then you are tired. When you are tired, you want to rest; but if you were to try to go to bed and sleep, sleep likely will not come. This is an important distinction because the strategies to reduce fatigue is different from strategies to reduce sleepiness.

This distinction is also important because insomnia is a disorder of fatigue, not sleepiness. People with insomnia are tired not sleepy.

Woman stirring a cup of coffee.
Tired? or Sleepy? (or both!)

Energy as a generator, not a battery

Often we think of energy like a battery that we spend up via engaging in activities throughout the day. In reality, energy is more like a generator and we have to give a little to get a little. Has there ever been a time where you did not want to do something because you were feeling tired – like going for a walk? But when you went for that walk anyways you actually felt a little better afterwards? That’s the generator at work! Below, I’ll discuss a few (of the many) possible reasons why someone can feel fatigued.

Fatigue is multifaceted

There are a million and one reasons that someone can feel tired throughout the day. People often attribute it to poor sleep, but sleep is just one of the reasons why people feel worse for wear during the day. Consequently, it is important to be a curious scientist in determining what is causing your fatigue:

1. Too little activity. As we discussed with the battery-generator analogy, fatigue pulls for rest. People who are tired want to stay inside all day and lie on their couch or bed. However, the increased rest counterproductively maintains our lack of energy. Therefore, it is sometimes important to engage in certain behaviours in spite of how we feel to get that generator rolling!

2. Too much activity. On the other hand, too much activity can also lead to fatigue. If you are always on the go 24-hours a day, that is going to contribute to a build-up of fatigue. Therefore, a balance between too much and too little activity is going to be important.

3. Not enough light exposure. Light is an important cue to help set our internal clock and get us up and ready for the day. Getting some light exposure, especially in the morning will help with energy levels.

4. Poor diet / lack of hydration. Unsurprisingly, improper diet and lack of hydration can also impact how we feel during the day. Consistent nutrition and water intake is essential in improving your energy levels.

5. Caffeine rebound. Although a couple cups of coffee in the morning/early afternoon can be helpful in getting your day started, people can experience caffeine withdrawal or a kick-back later in the afternoon once the caffeine has reached its half-life. Therefore, it is important to not rely on caffeine as your only source of energy!

6. Sleep. Poor and inconsistent sleep can absolutely contribute to lower energy levels. Ensuring good sleep health and using strategies to manage sleep inertia (i.e., feelings of grogginess when we wake up in the morning because sleep chemicals are still in our system) can be helpful to beat fatigue. Check out this post on three causes of insomnia to see how you can improve your sleep!

7. Anxiety and depression. Psychological problems can also contribute to fatigue. In fact, depression and generalized anxiety disorder both have fatigue as a listed symptom to support a diagnosis. Make sure to consult with a mental health professional if you notice that your fatigue is associated with anxiety or mood (or another psychological condition).   

8. Medical conditions and deficiencies. Finally, there are several medical conditions (e.g., anemia, high blood pressure) and deficiencies (e.g., iron, vitamin D) that can lead to feeling tired. It is important to regularly check with a medical professional to examine whether there are certain underlying conditions associated with your fatigue.

Caffeine can be helpful as a short-term solution for energy, but the kickback is sometimes problematic in the long-run!

Common strategies for fatigue management

Now that you know what might be causing your fatigue, here are a few strategies to begin tackling them. One acronym that we like to use is taking the H.E.L.M (Hydration, Eating, Light, Movement) of your fatigue. Make sure you are 1. well-hydrated 2. eating a balanced diet 3. exposing yourself to sunlight in the morning and 4. staying reasonably active.

Sleep expert Allison Harvey also has an effective strategy to reduce sleep inertia in the morning, known as RISE-UP that you can check out!

Although these can be some common strategies to target fatigue, ultimately the specific strategies that work for you will be individual. So be a curious detective! Investigate what might be causing your fatigue and experiment with a few different solutions. After engaging in each activity, check to see what your energy levels feel like.

If you find something that works for you, let me and others know in the comments!

If this post was helpful for you, please consider subscribing to the email list to continue learning more about evidence-based strategies to support your mental health journey!

Best wishes,



Kaplan, K. A., Talavera, D. C., & Harvey, A. G. (2018). Rise and shine: A treatment experiment testing a morning routine to decrease subjective sleep inertia in insomnia and bipolar disorder. Behaviour Research and Therapy111, 106-112.