Why Am I So Tired? The Most Common Causes Explained

In this article: provide 3-4 quick overviews that summarise the article.

• Fatigue is more than feeling tired. It can affect your physical energy, concentration, mood and motivation.
• There are many possible causes of tiredness, including poor sleep, stress, nutrition, hydration, activity levels and hormonal changes.
• Consistent sleep, balanced meals, hydration, stress management and regular movement may help.
• If tiredness is prolonged, severe, worsening, or affecting your quality of life, it's important to speak with a healthcare professional for further assessment.

You’ve had a full night’s sleep, but by mid-morning you’re feeling like you’re already running on empty. Feeling tired can affect more than just your energy levels. You might find it harder to concentrate, stay motivated, or simply get through the day with your usual energy. 

Feeling tired every now and then is common, especially if you’ve had a bad night's sleep or are stressed1. However, feeling tired all the time can be a sign that something may be affecting your energy, from daily habits to underlying health factors. 

In this guide, we’ll explore the meaning of fatigue, common causes, and some practical tips to help your body recover. From sleep quality and stress to nutrition and lifestyle habits, let’s take a closer look at what might be impacting your energy. 

What is fatigue?

Fatigue is more than feeling sleepy. It’s a feeling of constant tiredness or having low energy that doesn’t go away after you get a good night’s sleep2. Persistent fatigue affects between 5 and 20% of people and is twice as common in women as men3. 

Fatigue can affect people in different ways. Some may feel it physically, with symptoms like low energy or heaviness in the body. Others may notice mental effects, including difficulty concentrating or staying focused. There can also be emotional signs, such as irritability and low motivation¹. 

Fatigue symptoms

Fatigue tends to build slowly, with several factors adding up over time4. Here are some common symptoms5: 

• A feeling of being overly tired
• Tiredness that does not get better with rest
• Growing tired after starting an activity
• Daytime sleepiness
• Irritability or other negative changes to mood
• Difficulty focussing 

For some people, fatigue can be mild and pass with consistent rest. For others, it can feel like extreme fatigue that lingers day after day. Feelings of fatigue can also shift depending on stress levels, sleep and daily demands1 6 .

What causes tiredness and fatigue?

Daily life can place real demands on your energy. Poor sleep, high stress and busy schedules can often feed into each other, which is why it can be difficult to pinpoint the exact cause of fatigue3 7.

From sleep and stress to nutrition and exercise, below are some of the most common causes of feeling tired all the time.

Sleep and recovery

Sleep is one of the most direct contributors to your daily energy. A good night's sleep can leave you feeling rested and ready for the day, while a rough night can leave you groggy and tired. Interrupted sleep, inconsistent routines, and poor sleep quality can all contribute to fatigue⁸. 

Your body relies on two systems working together: sleep pressure and your circadian rhythm9. Your sleep pressure builds as you’re awake. Your circadian rhythm is an internal cycle across 24 hours, resetting daily using cues like light and dark. When these systems fall out of sync, it can disrupt your sleep and contribute to fatigue 9. 

Stress, overwhelm and mental fatigue

Stress affects your body in different ways. During periods of stress, cortisol and other stress hormones can rise as part of the body's stress response. Ongoing stress can also affect how you feel day to day, contributing to symptoms such as poor concentration, irritability, and frustration¹⁰. 

Some people describe this as feeling ‘wired, but tired’. They feel overstimulated mentally, but physically exhausted. 

Nutrition and hydration

What and when you eat can play a role in your daytime energy. Irregular eating patterns, skipping meals - especially breakfast - have been linked to low mood and fatigue11 12. 

Hydration also matters, playing a role in energy metabolism and physical performance. Even mild dehydration can leave you feeling more tired than usual13. 

Movement and physical activity

Your activity levels can also influence how you feel. One study found that people who were more physically active reported a lower risk of low energy and fatigue than those who were sedentary¹⁴. 

However, too much physical activity or movement can also lead to fatigue. Overtraining without sufficient recovery can impact your energy levels15. The key is to find a sustainable level of regular movement, while allowing time for recovery. 

Hormones and life stages

Hormonal shifts across different life stages can also play a role in fatigue. Perimenopause is often associated with symptoms including brain fog and fatigue¹⁶, while hormonal changes during menopause can affect sleep and energy levels¹⁷. 

Pregnancy is another example. In fact, 94% of women in one study experienced fatigue at one point during their pregnancy, with fatigue rising across trimesters as sleep quality declined18.

Illness, recovery and underlying health factors

Sometimes fatigue is just simply tied to illness, recovery from illness, or an underlying health condition. If your fatigue feels persistent, severe, is getting worse, or is disrupting your daily life, it's worth speaking with a health professional rather than waiting it out.

How to support your energy levels throughout the day 

There isn’t a single fix for fatigue, but a few habits may help support your energy over time. These include: 

• Keeping a consistent sleep routine with similar wake and sleep times
• Eating balanced meals at regular intervals
• Staying hydrated 
• Managing stress where possible
• Spending time outdoors19
• Building in gentle, regular movement (aim for around 150 to 300 minutes of moderate-intensity per week20).

Navigating fatigue day to day 

Your energy naturally fluctuates and some days will feel more draining than others. Those fluctuations are a normal part of how your body responds to sleep, stress, and daily demands and aren't always a sign that something is wrong. But consistent habits around sleep, movement, nutrition, and stress can help support your energy over time. 

Explore more articles on the link between sleep and immune health and how screen time affects your sleep on The Swisse Wellness Hub. 

References:

1. Billones, R, et.al. (2021). Brain, Behavior, & Immunity - Health, 15(100266), 100266. https://doi.org/10.1016/j.bbih.2021.100266
2. Emsellem, H.A, et.al. (2025). Health and Quality of Life Outcomes, 23(1), 26. https://doi.org/10.1186/s12955-025-02355-1
3. Sharpe, M. (2002). BMJ, 325(7362), 480–483. https://doi.org/10.1136/bmj.325.7362.480
4. Charonitis, M, et.al. (2024). Psychologica Belgica, 64(1), 85–107. https://doi.org/10.5334/pb.1259
5. Healthdirect Australia. Healthdirect Australia. Last reviewed August 2024. https://www.healthdirect.gov.au/fatigue
6. Clemson, L, et.al. (2013). In Encyclopedia of Behavioral Medicine (pp. 793–796). Springer. https://doi.org/10.1007/978-1-4419-1005-9_400
7. Tornero-Aguilera, J.F, et.al. (2022). International Journal of Environmental Research and Public Health, 19(7), 3909. https://doi.org/10.3390/ijerph19073909
8. Meng, Y, et.al. (2025). Frontiers in Public Health, 13, 1530988. https://doi.org/10.3389/fpubh.2025.1530988
9. Basit, H., Damhoff, T.C., & Huecker, M.R. (2023). In StatPearls. StatPearls Publishing.
10. Chu, B, et.al. (2024). In StatPearls. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK541120/
11. Tahara, Y, et.al. (2021). Nutrients, 13(8), 2775. https://doi.org/10.3390/nu13082775
12. Azzolino, D, et.al. (2020). Nutrients, 12(2), 444. https://doi.org/10.3390/nu12020444
13. Popkin, B.M., D'Anci, K.E., & Rosenberg, I.H. (2010). Nutrition Reviews, 68(8), 439–458. https://doi.org/10.1111/j.1753-4887.2010.00304.x
14. Puetz, T.W. (2006). Sports Medicine, 36(9), 767–780. https://doi.org/10.2165/00007256-200636090-00004
15. Budgett, R. (1998). British Journal of Sports Medicine, 32(2), 107–110. https://doi.org/10.1136/bjsm.32.2.107
16. Cutts, B.A., & Fennessy, K. (2025). Research and Practice in Thrombosis and Haemostasis, 9(2), 102698. https://doi.org/10.1016/j.rpth.2025.102698
17. Carlson, K., & Vadakekut, E.S. (2026). In StatPearls. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK507826/
18. Effati-Daryani, F, et.al. (2021). Sleep Science, 14(Special 1), 69–74. https://doi.org/10.5935/1984-0063.20200091
19. Twohig-Bennett, C., & Jones, A. (2018). Environmental Research, 166, 628–637. https://doi.org/10.1016/j.envres.2018.06.030
20. World Health Organization. (2020). https://www.ncbi.nlm.nih.gov/books/NBK566