Where do constant fatigue and lack of energy come from? Causes and ways to regain vitality

Article updated 07/03/2026

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Constant fatigue most often results from a combination of several factors simultaneously: deficiencies in iron, magnesium, or B vitamins, poor sleep quality, chronic stress, and unstable blood sugar levels. In most cases, it can be effectively reduced – first by diagnostics ruling out medical causes, then by specific changes in diet, sleep, activity, and supplementation.

In this article, you will find: a complete list of causes of fatigue along with their mechanisms, a set of tests worth starting with for diagnosis, and proven ways to regain energy – from diet, through sleep and exercise, to herbs and supplementation. The article will be useful for both those who are just looking for the cause of their fatigue and those who already know the diagnosis and are looking for practical solutions.

1. What is chronic fatigue and how does it differ from ordinary tiredness?

Chronic fatigue is a state of exhaustion that persists despite rest and sleep, usually lasting longer than a month, and in extreme cases – several or even a dozen months. Unlike ordinary fatigue after exertion, it does not disappear after a good night's sleep or a day off from duties.

The key difference lies in the body's response to regeneration. Ordinary fatigue is a natural signal – the body asks for rest, and after receiving it, returns to normal. Chronic fatigue works differently: despite an adequate amount of sleep, reduced obligations, or even a vacation, the feeling of exhaustion returns or does not subside at all. It is often accompanied by additional symptoms – difficulty concentrating, low mood, muscle and joint pain, or increased susceptibility to infections.

1.1. Physiological fatigue versus chronic exhaustion – how to distinguish them?

The table below shows the most important differences between the two states:

Scroll right to see the full table (on mobile devices) →

1.2. What is Chronic Fatigue Syndrome (CFS/ME)?

Chronic Fatigue Syndrome (CFS), also known as Myalgic Encephalomyelitis (ME), is a distinct medical condition recognized by the US Centers for Disease Control and Prevention (CDC) and the World Health Organization. It is estimated to affect 0.1–0.5% of the population, with the peak incidence between 20 and 45 years of age, and women being about three times more likely to be affected than men.^[1]

According to the criteria proposed by the Institute of Medicine in 2015, the diagnosis of CFS/ME requires the simultaneous occurrence of: a significant reduction in the ability to perform daily activities, post-exertional malaise, and unrefreshing sleep – along with cognitive impairment or orthostatic intolerance.^[2] The earlier, still widely used CDC definition from 1994 requires exhaustion to persist for at least 6 months and not be relieved by rest.^[3]

CFS/ME is diagnosed by exclusion – only after other possible causes of fatigue, such as hypothyroidism, anemia, or depression, have been ruled out. This distinguishes this syndrome from most cases of chronic fatigue, which have an identifiable and correctable cause, described in the next chapter.

1.3. When should fatigue prompt you to see a doctor?

Most cases of chronic fatigue can be effectively alleviated by changes in diet, sleep, and lifestyle, which we describe later in the article. However, there are situations in which fatigue is a signal requiring medical consultation, and not just a correction of habits.

Basic differential diagnostics allow for the exclusion or confirmation of the most common medical causes of fatigue – a set of tests to start with can be found in chapter 3.

2. What are the most common causes of chronic fatigue?

Chronic fatigue rarely has a single cause. Most often, it is the sum of several factors at once – nutritional deficiencies, poorer sleep quality, chronic stress, and lack of exercise. Below you will find the nine most common causes, where support for energy and vitality begins with their recognition.

2.1. What vitamin and mineral deficiencies most often cause fatigue?

Several nutrients have a direct, EFSA-confirmed connection with reducing feelings of fatigue and tiredness. Their deficiency is one of the first things worth checking.

Scroll right to see the full table (on mobile devices) →

A separate issue is coenzyme Q10, which participates in energy production at the cellular level in mitochondria. It currently does not have an EFSA-approved health claim regarding fatigue, but its role in the cell's respiratory chain is well-documented biochemically – preliminary studies suggest that its lower level may co-occur with poorer performance in some groups, e.g., older people.

BICAPS Vitamin B Complex 120 capsules - ForMeds

2.2. How do sleep and circadian rhythm disorders affect fatigue?

Sleep is the body's main regeneration mechanism – it is during sleep that tissue repair processes and memory consolidation occur. Too little sleep, frequent awakenings at night, or irregular sleep and wake-up times dysregulate the circadian rhythm (biological clock), which translates into poorer rest quality even with a seemingly sufficient number of hours of sleep. The result is morning fatigue, drops in concentration during the day, and increased susceptibility to infections. Practical ways to improve sleep hygiene are described in detail in chapter 5.1.

2.3. Can chronic stress and high cortisol cause fatigue?

Short-term stress mobilizes the body to act – it's a natural "fight or flight" response. The problem arises when the state of tension lasts for weeks or months. Constantly elevated levels of cortisol, the main stress hormone, are associated with poorer sleep quality, a greater craving for sugary and highly processed foods, and a feeling of chronic exhaustion that does not pass despite rest.

If you suspect that stress and elevated cortisol are behind your fatigue, it is worth checking out our separate article: How to naturally lower cortisol? Diet, herbs, supplements and lifestyle – you will find in-depth information on this topic there.

2.4. How do thyroid diseases and hormonal imbalances affect energy?

The thyroid regulates the metabolic rate of the entire body. Hypothyroidism (including Hashimoto's disease) slows down metabolism, which manifests itself, among other things, as drowsiness, weight gain, a feeling of cold, and a decrease in energy lasting throughout the day – regardless of the amount of sleep. Iodine contributes to the normal production of thyroid hormones and the proper functioning of the thyroid, therefore its adequate supply is important for maintaining normal metabolism.

BICAPS KELP Iodine 60 capsules - ForMeds

If you suspect you have thyroid problems, it's worth checking out our guide: What to eat with Hashimoto's? A diet supporting thyroid function. However, a definitive diagnosis always requires hormonal tests – their set is described in chapter 3.1.

2.5. How do insulin resistance and blood sugar fluctuations cause fatigue?

After a meal rich in simple sugars (sweets, white bread, sweetened drinks), blood glucose levels rise sharply, and then fall just as sharply. We feel this drop as sudden drowsiness and a decrease in concentration, especially after lunch. In people with insulin resistance – a condition in which cells respond less effectively to insulin – these fluctuations are even more pronounced, and the accompanying fatigue is often one of the first noticeable symptoms, even before abnormal test results appear.

2.6. Can lack of physical activity or overtraining cause fatigue?

Paradoxically, both too little and too much exercise can lead to chronic fatigue. A sedentary lifestyle slows down circulation and metabolism, making even small tasks feel tiring. On the other hand, intense training without an adequate number of rest days can lead to overtraining – a state in which, despite regular exercise, energy levels systematically decrease, sleep quality deteriorates, and immunity to infections decreases. How to find the golden mean between the two is described in chapter 5.2.

2.7. How does dehydration affect energy levels?

Even mild dehydration – around 1–2% of body weight – can reduce concentration and deepen feelings of fatigue. Water participates in the transport of nutrients and oxygen to cells and in the removal of metabolic waste products, which is why its deficiency affects well-being faster than one might expect. Practical tips on hydration can be found in chapter 4.3.

2.8. Can allergies and food intolerances cause chronic fatigue?

Food intolerances (e.g., to gluten or lactose) cause a state of chronic low-grade inflammation in the body, which the immune system expends energy resources to combat. In people with undiagnosed intolerance, fatigue is usually accompanied by additional symptoms – bloating, abdominal pain, headaches, or skin changes. Keeping a food diary and observing the body's reactions after meals is the simplest first step towards identifying the potential culprit.

2.9. Can medications, caffeine, and other stimulants worsen fatigue?

Some medications (including antihistamines, antidepressants, beta-blockers) list fatigue and drowsiness among their possible side effects. Excessive caffeine has the opposite of the intended effect – it provides a temporary boost but disrupts the quality of sleep at night, creating a vicious cycle: poorer sleep → greater fatigue → more coffee. Alcohol works similarly; despite its sedative effect, it significantly impairs the quality of deep sleep.

3. How to determine the cause of fatigue? What tests should be done?

A basic blood test panel can rule out or confirm the most common medical causes of chronic fatigue – anemia, hypothyroidism, inflammation, or glucose metabolism disorders. This is the first step before you start experimenting with diet and supplementation.

3.1. What is the basic test panel for chronic fatigue?

NICE CKS clinical guidelines for unexplained fatigue in adults recommend the following first-line tests: complete blood count (CBC), ferritin, thyroid function, liver and kidney function tests, CRP, and glucose levels, and, depending on the clinical picture, additionally vitamin D, B12, and folic acid.^[5] The table below shows what each of these tests specifically checks.

Scroll right to see the full table (on mobile devices) →

3.2. When should you consult a specialist?

The first step is usually a visit to a family doctor, who will order the basic tests described above. It is worth seeing a specialist when:

• the results of basic tests are abnormal – then your family doctor will refer you further (endocrinologist for thyroid problems, hematologist for anemia),
• fatigue is accompanied by symptoms described in section 1.3 as warning signs,
• all basic results are normal, but fatigue persists for more than several months – then it is worth considering diagnosis for CFS/ME or a psychiatric/psychological consultation, as fatigue can also be a symptom of mood disorders.

In the following sections, we describe what you can do yourself when tests show no abnormalities, and fatigue results from lifestyle, diet, or stress.

4. How does diet affect energy levels?

What you eat directly translates into how much energy you have during the day. Nutrient deficiencies, fluctuations in blood sugar levels, and inadequate hydration are some of the easiest causes of fatigue, described in section 2, to correct.

4.1. Which products and ingredients really boost energy?

Stable energy levels are best supported by foods that release glucose into the blood gradually, rather than causing sharp spikes and drops:

• Complex carbohydrates – groats, whole-grain products, and starchy vegetables provide sustained energy release.
• High-quality protein – eggs, fish, poultry, and plant-based sources like chickpeas, lentils, or other legumes stabilize blood sugar and support regeneration.
• Healthy fats – avocado, olive oil, nuts, and fatty sea fish support brain function and a lasting feeling of satiety.
• Iron-rich foods – spinach, parsley, quinoa, and beef help prevent iron-deficiency anemia.

Our store observations indicate that customers seeking energy support most often reach for a combination of buckwheat and millet groats with legumes – this is a simple way to get a wholesome, filling meal without sudden energy drops after eating.

4.2. How to stabilize blood sugar levels?

The key is to limit high glycemic index (GI) products in favor of those with low and medium GI, which do not cause sharp glucose fluctuations:

Scroll right to see the full table (on mobile devices) →

Regular, unskipped meals further help maintain stable glucose levels and avoid an afternoon energy crash.

4.3. How does hydration affect energy?

As mentioned in section 2.7, even mild dehydration reduces concentration and increases fatigue. The basis should be clean, filtered water, and for variety – herbal teas, which in addition to hydration, provide additional plant compounds. Caffeinated beverages (coffee, strong black tea) in moderate amounts do not significantly dehydrate, but in excess, they can disrupt sleep quality, indirectly deepening fatigue the next day.

4.4. What to avoid in your diet when experiencing fatigue?

Several eating habits particularly contribute to energy drops:

• Skipping breakfast or consuming high-GI products on an empty stomach in the morning.
• Excessive caffeine – provides a temporary stimulating effect but, in the long run, worsens sleep quality.
• Highly processed foods – poor in fiber and micronutrients, rich in simple sugars and trans fats.
• Alcohol in the evening – despite its sedative effect, it significantly impairs the quality of deep sleep.
• A diet low in fruits and vegetables – limits the supply of vitamins and minerals described in the table in section 2.1.

5. How do sleep, exercise, and stress management support body regeneration?

These are three pillars that, in practice, determine energy levels more than any supplement. Diet (section 4) provides the raw material, but sleep, exercise, and stress regulation determine whether the body manages to regenerate.

5.1. How to improve sleep quality?

Key principles of sleep hygiene:

• Consistent sleep and wake times – even on weekends, to avoid disrupting your biological clock.
• Limiting screens before bed – blue light inhibits melatonin production; it's best to put away your phone and computer an hour before bedtime.
• Dark and cool bedroom – a temperature of around 18–20°C promotes falling asleep.
• Light dinner – eaten at least 2–3 hours before bedtime, so digestion doesn't interfere with regeneration.
• Avoiding caffeine in the afternoon – its half-life is about 5–6 hours, so coffee drunk at 4:00 PM still has a stimulating effect in the evening.

If, despite following these rules, you still wake up tired, it's worth considering sleep apnea or restless legs syndrome as a possible cause – and refer back to the list of tests in section 3.1.

5.2. How much exercise is needed to have more energy?

As mentioned in section 2.6, both lack of exercise and overtraining reduce energy levels. A practical starting point is:

• Daily walk – 20–30 minutes outdoors improves circulation and oxygenation of the body.
• 2–3 moderate-intensity workouts per week – strength training, swimming, cycling, or Nordic walking.
• Minimum 1–2 days of regeneration between intense training sessions, especially for strength training.
• Morning activity – if you have a choice, working out or walking in the first half of the day more often improves energy levels for the rest of the day than an evening workout.

Signs of overtraining – a drop in performance despite regular workouts, worse sleep, increased susceptibility to infections – are a sign to reduce volume or intensity, not to add more sessions.

5.3. What stress reduction techniques really work?

In addition to physical activity, which itself lowers cortisol levels, it's worth incorporating:

• Breathing techniques – deep, slowed breathing activates the parasympathetic nervous system and quickly reduces tension.
• Meditation or mindfulness – even 10 minutes a day of regular practice improves stress management in the long run.
• Limiting stimuli in the evening – an "information detox" (social media, news) an hour before bed relieves the nervous system.
• Contact with nature – walks in the forest or gardening have a calming effect on the nervous system.

6. What herbs, adaptogens, and supplements support energy?

Supplementation only makes sense as a complement to diet, sleep, and exercise – not as a substitute for them. Below are the product categories most frequently chosen by our clients for chronic fatigue.

6.1. What are adaptogens and which ones are worth knowing?

Adaptogens are a group of plants traditionally used to support the body's resilience to stress and fatigue. Unlike caffeine, they do not work by providing a temporary boost, but by supporting the body's ability to adapt.

• Ashwagandha – one of the best-researched adaptogenic plants, traditionally used to support stress resilience.
• Ginseng – traditionally used to support vitality and concentration.
• Rhodiola rosea – traditionally used for feelings of mental and physical fatigue.
• Maca – a Peruvian root plant traditionally associated with supporting physical endurance.

All the above information is based on traditional use – none of these ingredients currently have an EFSA-approved health claim regarding fatigue reduction, which is why we deliberately do not attribute medicinal properties to them here.

BICAPS Ashwagandha 60 capsules - ForMeds

A full selection of adaptogenic plants can be found in our adaptogens category.

6.2. Which vitamins and minerals should be considered for supplementation?

The table below organizes the ingredients described more broadly in section 2.1, this time from the perspective of choosing a specific supplement:

Scroll right to see the full table (on mobile devices) →

Dosage should always be adjusted individually – preferably based on test results from section 3.1, not "by feel."

BICAPS MAG B6 Magnesium and Vitamin B6 60 capsules - ForMeds

OLICAPS Omega-3 60 capsules - ForMeds

6.3. What teas and infusions support energy and relaxation?

Mornings and evenings require different support – a gentle pick-me-up in the morning, and relaxation before sleep in the evening.

For an energizing start to the day, a combination of green tea with guarana and matcha works well – natural caffeine in such a blend is released more gently than from coffee alone, thanks to the L-theanine from the tea:

Green tea with acerola, guarana and matcha "Revitalization" BIO - Clipper

In the evening, a caffeine-free infusion that supports relaxation before sleep is better – a classic choice is a combination of lemon balm and lavender:

Lemon balm and lavender tea BIO (20 × 1.5 g) 30 g - Clipper

You can find a full selection of energizing teas in the green tea category, and a broader overview of all herbal infusions in section 4.3.

7. FAQ

7.1. Does a short nap during the day help with fatigue?

Yes, provided it lasts 15–20 minutes. A short energizing nap improves concentration and well-being without entering a deep sleep phase, from which it is more difficult to wake up. A nap longer than 30 minutes or taken late in the afternoon, however, can make it harder to fall asleep in the evening and worsen the problem described in section 5.1.

7.2. How long does it take to feel more energetic after making dietary and lifestyle changes?

The first effects – better sleep, smaller energy fluctuations during the day – are usually seen after 1–2 weeks of consistent changes. Correcting deficiencies (e.g., iron or vitamin D) confirmed by testing takes longer, usually 6–12 weeks of supplementation, depending on the initial degree of deficiency.

7.3. Can hormonal fluctuations during the menstrual cycle cause cyclical fatigue?

Yes. In the luteal phase (before menstruation), a drop in progesterone and estrogen can be felt as a decrease in energy, drowsiness, and poorer concentration in some women. If you notice that fatigue recurs at the same point in your cycle, it is also worth checking iron and ferritin levels – heavy periods are one of the most common causes of iron deficiency described in section 2.1.

7.4. What is the difference between mental and physical fatigue?

Physical fatigue is a feeling of muscle and body weakness after exertion, which usually subsides after rest. Mental fatigue manifests mainly as difficulty concentrating, "brain fog," and a drop in motivation, even without significant physical exertion. In practice, both types often coexist, especially with chronic stress described in section 2.3.

7.5. Is drinking coffee on an empty stomach in the morning a good idea for energy problems?

Not necessarily. In some people, coffee drunk on an empty stomach increases cortisol production, which is naturally highest in the first hour after waking up anyway. Drinking coffee 60–90 minutes after getting up, preferably after a meal, usually provides a more stable stimulating effect without a subsequent energy crash.

7.6. Can chronic fatigue also affect children and adolescents?

Yes, although it is less common than in adults. In children and teenagers, the most common causes are insufficient sleep, an intense growth period that increases the demand for iron and B vitamins, as well as the burden of school and extracurricular activities. Persistent fatigue in a child should always be consulted with a pediatrician.

8. Summary

Chronic fatigue rarely has a single cause – it is usually a sum of several factors at once: nutritional deficiencies, poorer sleep, chronic stress, and lack of exercise (section 2). Before reaching for supplements, it is worth starting with a basic set of tests (section 3) – this allows you to rule out or confirm medical causes of fatigue, rather than guessing.

If tests do not show abnormalities, the biggest difference is usually made by consistency in four areas: a diet that stabilizes blood sugar levels (section 4), sleep hygiene, regular moderate exercise, and stress management (section 5). Herbs, adaptogens, and supplements (section 6) can be a valuable addition to this process, but they cannot replace its foundations.

If fatigue is accompanied by the warning signs described in section 1.3, do not wait for the effects of lifestyle changes – consult a doctor.

9. Sources

1. Missailidis D. et al., Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Comprehensive Review – NCBI/PMC6787585
2. CDC, IOM 2015 Diagnostic Criteria – ME/CFS – cdc.gov
3. A comparison of health status in patients meeting alternative definitions for chronic fatigue syndrome/myalgic encephalomyelitis – NCBI/PMC4008489
4. Institute of Medicine, Beyond Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Redefining an Illness – NCBI Bookshelf/NBK284898
5. NICE, Clinical Knowledge Summary: Tiredness/fatigue in adults – cks.nice.org.uk
6. EFSA, Register of nutrition and health claims (basis for claims regarding iron, magnesium, vitamins B6, B12, C, and iodine in accordance with EU Regulation 432/2012) – ec.europa.eu