Fatigue is one of the most common reasons why women visit a doctor, yet it often remains unexplained or is dismissed with the advice to “get more sleep.” The truth is that there are many possible causes of chronic fatigue in women, and they are often hidden in hormones, nutrition, the nervous system, and lifestyle factors.
What is the difference between normal sleepiness and chronic fatigue?
Before exploring the causes, it is important to understand the difference. Normal sleepiness improves after a good night's rest. Chronic fatigue is a state of persistent exhaustion, lack of energy, and weakness that does not disappear even after long periods of sleep or rest.
A systematic meta-analysis of 91 studies involving more than 623,000 participants from around the world confirmed that women are statistically significantly more affected than men, with a higher risk ratio [1],[3].
This means that fatigue in women is not merely a subjective feeling, but a measurable, widespread, and often under-recognised health issue.
"Fatigue is one of the five most common reasons for visiting a general practitioner and is often an indicator of an emerging health condition." — Maisel et al., Deutsches Ärzteblatt International, 2021
10 Possible Reasons for Your Fatigue
Our emotions, hormones, and nervous system are not separate. The mind and body are deeply interconnected. A review article by Mathis (2021), published in the journal
Women (MDPI), describes fatigue in women as "a dense network of interconnected variables" that includes psychosocial, physical, cultural, and disease-related factors.
Let's look at the most common causes:
1. Hormonal fluctuations – menstrual cycle and menopause
Hormones are one of the most common and at the same time most overlooked causes of fatigue in women. A drop in estrogen levels before menstruation directly affects neurotransmitters such as serotonin, dopamine, and acetylcholine, which are essential for maintaining healthy sleep patterns and energy levels.
The result can be sleep disturbances, daytime drowsiness, and general weakness.
During menopause, fluctuations in estrogen and progesterone levels can cause hot flashes and night sweats, which significantly reduce sleep quality and contribute to chronic daytime fatigue.
2. Iron deficiency and low ferritin levels
Iron is essential for transporting oxygen throughout the body. When iron levels drop, cells receive less oxygen, and the body has to work much harder to produce energy. Heavy menstrual bleeding is a common cause of iron loss in women.
Read more about how estrogen and progesterone affect energy levels in our article:
Phases of the Menstrual Cycle
What is particularly important is that symptoms of iron deficiency often appear before true anemia develops.
3. Thyroid problems: hypothyroidism
Fatigue is one of the main symptoms of an underactive thyroid (hypothyroidism), a condition that affects significantly more women than men.[1] Symptoms often develop gradually and may also include sensitivity to cold, muscle and joint pain, weight gain, and low mood.
Because symptoms develop slowly, many women simply normalize them and attribute them to aging or stress. A clinical review published in the
Singapore Medical Journal (2022) identifies thyroid disorders as one of the most frequently overlooked causes of fatigue in primary healthcare.[4]
4. Chronic stress and cortisol dysregulation
When we experience ongoing stress, our nervous system remains in a state of fight-or-flight. This constant activation of the sympathetic nervous system can lead to prolonged elevation of cortisol levels.
Long-term exposure to stress can disrupt the hypothalamic-pituitary-adrenal (HPA) axis, resulting in deep, persistent exhaustion that is not relieved even by sleep. Mathis (2021) emphasizes that the nervous system operates through two main states: stress and relaxation (sympathetic and parasympathetic states), and prolonged dysregulation of this system can directly manifest as fatigue.
Learn more about how chronic stress and nervous system imbalance affect overall wellbeing in our article about
the vagus nerve and nervous system imbalance.
5. Vitamin D deficiency
Vitamin D plays an important role in muscle function, energy metabolism, and neurotransmitter regulation. A literature review published in
Nutrients (MDPI, 2024) found that vitamin D deficiency may contribute to fatigue through several mechanisms, including increased oxidative stress, inflammation, and imbalance between dopamine and serotonin.[5]
Because we spend a significant amount of time indoors, vitamin D deficiency is extremely common in Slovenia, especially during winter and spring.
6. Sleep disorders and poor sleep hygiene
Sleep quality is just as important as sleep duration.
Experts recommend 7 to 9 hours of sleep per night for adults. Lack of sleep does not only cause drowsiness but can also increase blood pressure, disrupt hormonal balance, and weaken the immune system.
7. Poor diet and blood sugar fluctuations
A diet high in simple carbohydrates and sugar can cause rapid spikes and drops in blood sugar levels.
These drops can manifest as sudden fatigue and brain fog. A lack of essential nutrients such as B vitamins, magnesium, and vitamin C can also contribute to feelings of exhaustion.
8. Dehydration
Even mild dehydration, amounting to only around 2% of body weight, can significantly affect cognitive function and cause feelings of fatigue, confusion, and difficulty concentrating.[6]
Many women simply do not drink enough water throughout the day, making this one of the simplest yet most overlooked causes of fatigue.
9. Depression and anxiety
Mental and physical health are inseparable. Maisel et al. (2021) confirm that depression accounts for 18.5% of chronic fatigue cases in primary healthcare and is one of the most common causes of persistent exhaustion.[1]
Women are twice as likely as men to develop depression.[2] Fatigue and lack of motivation are often among the first and most significant physical symptoms of depression and anxiety. When fatigue is accompanied by hopelessness, sadness, or loss of interest in activities that once brought joy, it may be a sign that it is time to seek professional support.
10. Chronic fatigue syndrome (ME/CFS) and long COVID
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex condition that causes extreme fatigue that does not improve with rest and often worsens after physical or mental exertion. It affects an estimated 17 to 24 million people worldwide, with women being significantly more affected than men. Similarly, many women experience long-lasting fatigue after COVID-19 infection (long COVID), which can persist for months and seriously affect quality of life.
Other Common but Often Overlooked Causes
In addition to the ten main causes, there are several other factors that healthcare professionals often assess when investigating chronic fatigue, but that readers rarely associate with their symptoms.
Vitamin B12 and folate deficiency. Vitamin B12 is essential for the production of red blood cells and the proper functioning of the nervous system. A deficiency can manifest as fatigue, brain fog, depression, and peripheral neuropathy. Folate deficiency (vitamin B9) can cause megaloblastic anemia, with fatigue being one of its main symptoms. Both deficiencies are more common among women who follow restrictive diets, take certain medications (such as metformin), or have absorption disorders.
Sleep apnea. Obstructive sleep apnea (OSA) often remains undiagnosed in women because it can present differently than in men. Instead of loud snoring, women are more likely to report insomnia, morning headaches, depression, and fatigue.
Medications as a cause of fatigue. Some commonly prescribed medications can have fatigue as a side effect, which patients often do not associate with the medication itself. Common examples include antihistamines (allergy medications), antidepressants, beta-blockers (medications for heart conditions and blood pressure), and benzodiazepines. If you have recently started taking a new medication and notice increased fatigue, discuss it with your doctor.
When a doctor evaluates a patient with chronic fatigue, targeted laboratory tests may be ordered based on the clinical assessment.
| Test |
What it checks |
Why it is important |
| Complete blood count (CBC) |
Hemoglobin, red blood cells, white blood cells |
Helps rule out anemia and infections |
| *Ferritin |
Iron stores in the body |
Deficiency is common in women, even without anemia |
| TSH (thyroid-stimulating hormone) |
Thyroid function |
Hypothyroidism is a common and treatable cause of fatigue |
| Vitamin D |
Vitamin D levels |
Often deficient, especially during winter in Slovenia |
| Vitamin B12 and folate |
Nutritional vitamin levels |
Deficiency can cause fatigue and neurological symptoms |
| Electrolytes (Mg, K, Na) |
Mineral balance |
Magnesium deficiency is a common contributor to fatigue |
| CRP |
Inflammatory markers |
May indicate hidden inflammation or infection |
*Ferritin may be falsely elevated during inflammation.
**Note: Laboratory tests should always be recommended by a healthcare professional based on your individual clinical situation. The list above is for informational purposes only and does not replace medical advice.When Is It Time to See a Doctor?
Occasional fatigue is a normal response of the body to lack of sleep, stress, or increased physical and mental demands. However, if exhaustion persists for several weeks, affects your daily life, or occurs without an obvious reason, it is important to investigate the possible underlying causes.
Pay particular attention if fatigue is accompanied by hair loss, unexplained pain, weight gain, frequent infections, or a persistently low mood.
What Can I Do Myself? Practical Steps
Once you recognize that your fatigue is not just a temporary phase, it is time to take action. Your body has an extraordinary ability to regenerate and restore balance.
Support it with knowledge and practical steps.
Check your blood work. Visit your doctor and ask about testing ferritin, vitamin B12, folate, thyroid hormones (TSH), vitamin D, and blood sugar levels. These are often hidden but easily manageable causes of fatigue.
Calm your nervous system. Incorporate practices that activate the parasympathetic nervous system (the state responsible for rest and regeneration). Deep breathing, meditation, yoga, or simply spending time in nature are proven methods for reducing cortisol levels.
Optimize your nutrition. Focus on whole foods that help stabilize blood sugar levels. Include more protein, healthy fats, and vegetables, while reducing processed sugar and excessive caffeine intake.
Improve your sleep hygiene. Try to go to bed and wake up at the same time every day, including weekends. Limit exposure to blue light from screens before bedtime and make sure your bedroom is cool and dark.
Review your medications. If you are taking antihistamines, antidepressants, beta-blockers, or other medications and have noticed increased fatigue, discuss this with your doctor. There may be an alternative treatment option or a possible dose adjustment.
Set boundaries. Learn to say no. Excessive demands and suppressed emotions directly affect your energy levels and immune system. Taking care of yourself is not selfish — it is a foundation for everything else.
Frequently Asked Questions About Fatigue (FAQ)
Is it normal to feel extremely tired before my period?A certain level of fatigue before menstruation is normal, as declining estrogen levels can affect serotonin levels and sleep quality. However, extreme fatigue that prevents you from functioning normally may indicate iron deficiency caused by heavy bleeding or a significant case of premenstrual syndrome (PMS) that requires attention.
How do I know if I have an iron deficiency if I am not anaemic?Iron deficiency can cause significant symptoms, including fatigue, weakness, hair loss, and increased sensitivity to cold, even before true anaemia develops with low haemoglobin levels. For an accurate diagnosis, it is important to check blood ferritin levels and transferrin saturation (TSAT), not just haemoglobin.
Can stress really cause physical fatigue?Absolutely. Chronic stress keeps your nervous system in a constant state of alert, which depletes energy reserves and can lead to cortisol dysregulation. This eventually manifests as deep physical exhaustion that is not relieved even by sleep. A body that has functioned under stress for years needs time and support to regenerate.
Is fatigue more common in women than in men?Yes. A systematic meta-analysis of 91 studies involving more than 623,000 participants showed that women are statistically significantly more likely to experience fatigue than men.
When is fatigue a serious health warning sign?Fatigue that lasts longer than two to three weeks, does not improve with rest, or is accompanied by other symptoms (such as hair loss, pain, changes in body weight, more frequent infections, or depressed mood) requires medical evaluation and appropriate laboratory testing.
Is sleep apnoea really a cause of fatigue in women?Yes, and it happens more often than many people realise. Women with obstructive sleep apnoea often do not have loud snoring but instead report insomnia, morning headaches, and daytime fatigue. Because their symptoms can differ from the "classic" presentation, diagnosis in women is often delayed.
Summary
Chronic fatigue is not a normal condition that you should simply accept as part of everyday life. It is a signal from your body that something may be out of balance. As we have seen throughout this article, the causes of fatigue in women are numerous and often interconnected: hormonal fluctuations, deficiencies of essential nutrients, sleep disorders, chronic stress, hidden health conditions, or even medications taken on a daily basis.
Timely diagnosis is essential. Simple laboratory tests such as ferritin, TSH, vitamin D, vitamin B12, folate, and glucose can often reveal underlying causes that can be effectively treated. Many women live with fatigue for years without realizing that the cause may be something as treatable as low ferritin levels or an undiagnosed thyroid disorder.
It is also important to understand that fatigue rarely has a single cause. It is often the result of a combination of factors that together exceed the body's ability to recover and maintain balance. Therefore, a holistic approach that includes both laboratory diagnostics and lifestyle changes is often the most effective solution.
*Note: This article is for informational purposes only and does not replace medical consultation, diagnosis, or treatment. If you experience chronic symptoms, medical conditions, pregnancy, use of medications, or severe symptoms, consult a doctor or another qualified healthcare professional.
References and scientific literature:
[1] Maisel, P., Baum, E., & Donner-Banzhoff, N. (2021). Fatigue as the Chief Complaint: Epidemiology, Causes, Diagnosis, and Treatment. Deutsches Ärzteblatt International, 118(33–34), 566–576.
[2] Mathis, B. J. (2021). The Intricate Web of Fatigue in Women. Women, 1(4), 267–279.
[3] Tamanna, S., Ullah, M. I., Iftekhar, R., & Shamsuddin, L. (2026). Sleep Disturbances in Menopause: Neuroendocrine Mechanisms and Clinical Implications. Physiologia, 6(2), 22.
[4] Ho, D. C. H., & Zheng, R. M. (2022). Approach to fatigue in primary care. Singapore Medical Journal, 63(11), 674–678.
[5] Di Molfetta, I. V., Bordoni, L., Gabbianelli, R., Sagratini, G., & Alessandroni, L. (2024). Vitamin D and Its Role on the Fatigue Mitigation: A Narrative Review. Nutrients, 16(2), 221.
[6] Zhang, N., Du, S. M., Zhang, J. F., & Ma, G. S. (2019). Effects of Dehydration and Rehydration on Cognitive Performance and Mood among Male College Students in Cangzhou, China: A Self-Controlled Trial. International Journal of Environmental Research and Public Health, 16(11), 1891.