Fatigue: Why You're Always Tired and What to Do About It
Fatigue is one of the most common reasons people seek help, yet it is also one of the most misunderstood symptoms. Many people are told their blood tests are "normal," their stress is the problem, or they simply need more sleep. Sometimes that is true. Often, it is incomplete.
Fatigue is not just feeling sleepy. It can feel like waking up unrefreshed, dragging through the day, needing caffeine to function, crashing after exercise, struggling to concentrate, or feeling physically heavy for no clear reason. In clinical practice, fatigue is rarely caused by one thing. It is usually the result of several systems under strain at the same time.
A systematic review on tiredness in primary care found that fatigue can be linked to a wide range of causes including anaemia, serious organic disease, depression, and chronic fatigue syndrome, which highlights why persistent tiredness deserves proper assessment rather than guesswork. (BMC Primary Care, 2016)
At Wave Functional Health, we look at fatigue through a systems-based lens. Instead of asking "What supplement gives energy?" we ask "Why is the body failing to produce, regulate, or recover energy properly?"
What Is Fatigue Really Telling You?
Fatigue is a signal. It may be your body telling you that your sleep is poor, your nervous system is overloaded, your blood sugar is unstable, your mitochondria are underperforming, your nutrients are depleted, your hormones are out of rhythm, or your immune system is still responding to something.
This is why two people can both say "I'm tired all the time" but need completely different strategies.
One person may be exhausted because of low iron stores. Another may have post-viral fatigue. Another may be running on stress hormones all day and crashing at night. Another may have sleep apnoea, poor thyroid conversion, chronic inflammation, or under-fuelling from years of dieting.
Fatigue generally falls into three broad categories. Secondary fatigue is caused by an identifiable underlying medical condition and typically resolves once that condition is treated. Physiological fatigue results from lifestyle imbalances such as poor sleep, overtraining, or chronic stress, and often improves with rest and lifestyle correction. Chronic fatigue persists for six or more months, is not relieved by rest, and significantly impairs daily functioning. This third category requires the most thorough investigation.
Secondary Fatigue
Caused by an identifiable underlying medical condition. Typically resolves once that condition is properly identified and treated.
Physiological Fatigue
Results from lifestyle imbalances such as poor sleep, overtraining, or chronic stress. Often improves with rest and lifestyle correction.
Chronic Fatigue
Persists for six or more months, is not relieved by rest, and significantly impairs daily functioning. Requires the most thorough investigation.
The key is to stop treating fatigue as a vague complaint and start treating it as a pattern that can be investigated.
Common Causes of Fatigue
Poor Sleep Quality
Eight hours in bed does not guarantee restored energy. Sleep architecture, blood sugar overnight, and sleep apnoea all matter.
Mitochondrial Dysfunction
When mitochondria cannot produce ATP efficiently, the body literally runs out of cellular fuel regardless of how much you sleep or eat.
Iron and Nutrient Deficiency
Low ferritin, B12, folate, vitamin D, magnesium, and zinc all have well-established roles in energy metabolism and oxygen transport.
Blood Sugar Dysregulation
Energy crashes are often blood sugar crashes in disguise. Unstable glucose leads to predictable mid-morning and afternoon fatigue.
Thyroid and Hormonal Factors
A TSH alone does not tell the full story. T3 availability at the tissue level is the critical variable standard testing frequently misses.
Adrenal Dysfunction
Dysregulated cortisol patterns leave you wired at night and flat in the morning, directly suppressing mitochondrial energy production.
Nervous System Overload
A chronically activated stress state makes recovery inefficient. Low HRV, poor sleep, and afternoon crashes are common patterns.
Gut Health and Inflammation
Dysbiosis and leaky gut drive chronic low-grade inflammation that places enormous ongoing demand on the body's energy resources.
Post-Viral Fatigue
After COVID-19, Epstein-Barr, Ross River, and other infections, fatigue can persist long after the acute illness has resolved.
1. Poor Sleep Quality
You can spend eight hours in bed and still wake up tired if your sleep quality is poor. Adults generally need at least seven hours of sleep per night, and insufficient sleep is linked with poor health outcomes. (CDC)
Common sleep-related drivers of fatigue include going to bed too late, screen exposure at night, alcohol close to bedtime, blood sugar crashes overnight, sleep apnoea, pain or discomfort, stress and racing thoughts, and a poor sleep environment.
A useful question is not just "How many hours did I sleep?" but "Did I wake feeling restored?"
2. The Mitochondria Connection: Your Cells Are Running Out of Fuel
At the core of most persistent fatigue is a story happening at the cellular level. Dr. Joseph Mercola, in his book Your Guide to Cellular Health (2024), argues that mitochondrial dysfunction sits at the root of fatigue for a significant portion of the population. Mitochondria are the energy factories inside nearly every cell in your body. Their primary job is to produce ATP, the molecule that powers virtually every biological function, from muscle contraction to hormone synthesis to brain signalling.
When mitochondrial function is impaired, ATP output drops. Research published in the International Journal of Clinical and Experimental Medicine found a strong correlation between the degree of mitochondrial dysfunction and illness severity in CFS patients, with 70 out of 71 patients showing measurable ATP impairment. (Myhill et al., 2009) The result is a body that is quite literally running low on fuel. You can eat well, sleep adequately, and still feel exhausted because the problem is not about how much energy is going in. It is about whether your cells can actually convert that energy into something usable.
Mercola identifies four key stressors that consistently impair mitochondrial energy production: excess omega-6 seed oils, environmental toxins and endocrine disruptors, chronic psychological stress, and disrupted circadian rhythms. A 2024 paper in Frontiers in Physiology reinforces this, noting that mitochondrial dysfunction contributes to chronic inflammation and energy deficiency through disrupted respiratory complex assembly. (Hwang et al., 2025)
3. Iron Deficiency and Low Nutrient Status
Low iron is one of the most overlooked causes of fatigue, especially in women, athletes, people with gut issues, and anyone with heavy menstrual bleeding. Importantly, iron deficiency can exist before anaemia shows up on a standard full blood count. Haemoglobin may look normal while ferritin, your iron storage marker, is low.
Other nutrient issues can also contribute to fatigue, including low B12, folate, vitamin D, magnesium, zinc, protein, omega-3 fats, and key amino acids. A comprehensive narrative review in Nutrients (2020) concluded that B vitamins, iron, magnesium, and zinc have well-established roles in energy-yielding metabolism, oxygen transport, and neuronal function, and that inadequate status in any of these reliably produces fatigue and cognitive impairment. (Tardy et al., 2020)
Vitamin D specifically has been shown to matter. A double-blind randomised placebo-controlled trial found improvement in self-perceived fatigue after vitamin D3 supplementation in people with deficiency. (PMC5207540)
4. Blood Sugar Dysregulation
Energy crashes are often blood sugar crashes in disguise. If you feel tired mid-morning, shaky when meals are delayed, sleepy after lunch, or crave sugar in the afternoon, your glucose regulation may need attention.
Common patterns include a high-carbohydrate breakfast with low protein, skipping meals, under-eating during the day, too much caffeine, insulin resistance, poor muscle mass, and high stress affecting glucose control. Stable blood sugar is one of the foundations of stable energy.
5. Thyroid and Hormonal Factors
Thyroid hormone helps regulate metabolic rate, body temperature, bowel motility, mood, and energy. A 2024 review in The Lancet confirms that fatigue, lethargy, weight gain, and cold intolerance are among the most common presentations of hypothyroidism, though these symptoms are frequently missed on standard biochemical testing. (The Lancet, 2024)
A basic TSH alone does not always tell the full story. Research published in Cureus (2025) highlights that a significant proportion of hypothyroid patients continue to experience fatigue and cognitive difficulties even after TSH normalisation, suggesting that tissue-level T3 availability is the critical variable that standard testing fails to capture. (Mazza, 2025)
Hormonal changes beyond the thyroid can also contribute to fatigue. Perimenopause, menopause, low testosterone, low DHEA, adrenal rhythm disruption, and chronic stress can all affect energy, motivation, sleep, and recovery.
6. Adrenal Dysfunction and the Cortisol Drain
Your adrenal glands produce cortisol, your primary stress hormone, which governs morning alertness, immune regulation, blood sugar balance, and inflammation response. Under prolonged stress, whether physical, emotional, or biochemical, this system becomes dysregulated.
A 2024 review published in Frontiers in Endocrinology confirmed that CFS patients consistently show attenuated diurnal cortisol variation, weakened HPA axis responsiveness, and increased negative feedback signalling. (Zhang and Wang, 2024) A landmark review in Nature Reviews Endocrinology found that HPA axis dysfunction in CFS is associated with worse symptoms, greater disability, and poorer outcomes with standard treatments. (Tomas et al., 2012)
The consequence is disrupted cortisol patterns, often elevated at night keeping you wired and unable to sleep deeply, and blunted in the morning making it nearly impossible to feel alert and motivated. Chronic cortisol dysregulation also directly suppresses mitochondrial activity, creating a compounding cycle where stress drains energy and low energy makes stress worse.
7. Nervous System Overload
Many people with fatigue are not lazy. They are stuck in a high-output stress state.
When the nervous system is constantly switched on, the body becomes less efficient at recovery. This may show up as being wired but tired, poor sleep despite exhaustion, low heart rate variability, shallow breathing, muscle tension, anxiety or irritability, afternoon crashes, and poor exercise recovery.
The body cannot heal well when it never feels safe.
8. Gut Health and the Fatigue Loop
A compromised gut microbiome creates a low-grade inflammatory state that places enormous ongoing demand on the body's resources. A 2024 review in Frontiers in Physiology confirmed that when intestinal permeability increases, bacterial lipopolysaccharides (LPS) enter systemic circulation and trigger chronic low-grade inflammation through the TLR4 signalling pathway. (Dmytriv et al., 2024) These endotoxins also act directly on mitochondria, reducing their capacity to produce energy.
Dysbiosis, SIBO (small intestinal bacterial overgrowth), and unresolved parasitic infections all create metabolic noise that the immune system must constantly manage. The energy cost of running a chronically activated immune response is significant, and it rarely shows up clearly on standard bloodwork.
9. Post-Viral and Immune-Related Fatigue
Some people develop fatigue after viral infections, including COVID-19, Epstein-Barr virus, Ross River virus, influenza, or other infections. A recent systematic review and meta-analysis concluded that long COVID remains a continuing global health challenge, with fatigue among the most commonly reported persistent symptoms. (PubMed, 2024)
For some people, fatigue is not improved by simply pushing harder. In conditions such as ME/CFS, NICE guidelines recommend energy management and caution against fixed incremental exercise programs that ignore energy limits and symptom flares. (NCBI) If someone experiences post-exertional malaise, meaning symptoms worsen after physical or mental effort, the approach must be paced carefully.
What Should You Test When Fatigue Persists?
Testing should be guided by history, symptoms, and clinical context. Useful areas to investigate may include a full blood count, iron studies including ferritin, B12 and folate, vitamin D, a full thyroid panel including TSH, free T4, free T3, reverse T3, and thyroid antibodies where appropriate, fasting glucose, insulin and HbA1c, liver and kidney function, inflammatory markers such as CRP and ESR, electrolytes and minerals, hormone testing where clinically indicated, sleep assessment if snoring or waking unrefreshed is present, and gut testing where digestive symptoms are present.
| Test | What it reveals | Relevant for |
|---|---|---|
| Full blood count and iron studies including ferritin | Anaemia, iron storage levels, red blood cell health | Fatigue, brain fog, breathlessness, heavy periods |
| B12, folate, vitamin D | Key nutrient status for energy metabolism and neurological function | Fatigue, mood changes, cognitive impairment |
| Full thyroid panel TSH, free T4, free T3, reverse T3, antibodies |
Complete picture of thyroid conversion and immune-related thyroid dysfunction | Fatigue, weight changes, temperature sensitivity, low mood |
| Fasting glucose, insulin, HbA1c | Blood sugar regulation, insulin resistance, metabolic health | Energy crashes, sugar cravings, afternoon fatigue |
| Inflammatory markers CRP, ESR |
Systemic inflammation indicating immune activation or infection | Persistent fatigue, pain, post-viral presentations |
| DUTCH hormone panel | Cortisol patterns across the day, sex hormone metabolism, adrenal rhythm | Wired but tired, poor morning energy, hormonal fatigue |
| GI MAP stool analysis | Microbiome diversity, pathogens, gut permeability, digestive function | Fatigue with gut symptoms, post-viral, immune-related fatigue |
| HRV assessment | Autonomic nervous system function, physiological stress load, recovery capacity | All fatigue presentations — objective measure of system load |
The goal is not to order every test possible. The goal is to ask better questions and use testing to confirm the most likely drivers.
Practical Tips to Improve Energy
Start your day with protein. A high-protein breakfast can support blood sugar stability, reduce cravings, and improve satiety through the morning. Aim for 25 to 40 grams at breakfast from eggs, chicken, Greek yoghurt if tolerated, protein smoothies, or leftovers from dinner.
Get morning light. Five to fifteen minutes outside in the morning helps anchor your circadian rhythm, supports cortisol timing, improves melatonin production at night, and lifts mood. You do not need direct sun exposure, just natural light safely into your eyes.
Stop relying on caffeine as a crutch. Caffeine is not bad, but using it to override exhaustion can create a bigger crash later. Keep caffeine before midday and avoid using it instead of food, hydration, or rest.
Move, but match your capacity. For many people, gentle aerobic work such as walking, cycling, or swimming can improve energy over time. However, if exercise makes you crash for days, do not force it. That may indicate post-exertional malaise or an underlying issue that needs a different approach first.
Eat enough food. Many exhausted people are under-fuelled. This is especially common in high achievers, busy parents, athletes, and people trying to lose weight. If your body is not getting enough protein, carbohydrates, minerals, and total calories, fatigue is a predictable outcome.
Support minerals and hydration. Dehydration and low electrolytes can worsen fatigue, headaches, and poor exercise tolerance. Start with water, mineral-rich foods, and adequate salt intake unless you have been medically advised to restrict sodium.
Protect your evening. Dim lights after dinner, reduce screens 60 minutes before bed, keep the bedroom cool and dark, avoid heavy meals close to bedtime, and keep sleep and wake times consistent across the week.
Track your patterns. Track energy for two weeks noting sleep, meals, caffeine, exercise, stress, bowel habits, and energy crashes. Patterns often reveal what single blood tests miss.
Reduce seed oil intake. Oils rich in linoleic acid, found in most packaged foods and restaurant cooking, are linked to mitochondrial membrane damage and impaired ATP production. Swapping to extra virgin olive oil, coconut oil, ghee, or butter is a practical and high-leverage change.
Consider a DUTCH hormone panel. If you have been fatigued for an extended period and sleep does not restore you, a DUTCH panel can map cortisol patterns across the day and reveal whether adrenal rhythm disruption is part of your picture. This is more informative than a single morning cortisol blood draw.
Start with protein at breakfast
25 to 40 grams of protein at breakfast stabilises blood sugar, reduces cravings, and supports morning energy through until lunch.
Get morning light
5 to 15 minutes of natural light in the morning anchors your circadian rhythm, supports cortisol timing, and improves melatonin production at night.
Stop relying on caffeine
Keep caffeine before midday and avoid using it as a substitute for food, hydration, or rest. Using it to override exhaustion creates a bigger crash later.
Move within your capacity
Gentle aerobic movement can improve energy over time. But if exercise makes you crash for days do not force it. That signal requires a different approach first.
Eat enough food
Many exhausted people are under-fuelled. If the body is not getting adequate protein, carbohydrates, minerals, and total calories, fatigue is a predictable outcome.
Support minerals and hydration
Dehydration and low electrolytes worsen fatigue, headaches, and poor exercise tolerance. Start with water, mineral-rich foods, and adequate salt intake.
Protect your evening
Dim lights after dinner, reduce screens 60 minutes before bed, keep the bedroom cool and dark, and maintain consistent sleep and wake times.
Track your patterns
Track energy for two weeks noting sleep, meals, caffeine, stress, and crashes. Patterns often reveal what single blood tests consistently miss.
Reduce seed oil intake
Oils high in linoleic acid are linked to mitochondrial membrane damage. Swap to extra virgin olive oil, coconut oil, ghee, or butter where possible.
Consider a DUTCH hormone panel
If fatigue persists and sleep does not restore you, a DUTCH panel maps cortisol patterns across the day and reveals adrenal rhythm disruption.
When Should You Get Help?
Seek medical assessment if fatigue is severe, persistent, worsening, or associated with unexplained weight loss, night sweats, fever, shortness of breath, chest pain, fainting, blood in stool, neurological symptoms, new pain, or significant mood changes.
Fatigue is common. That does not mean it is normal.
Seek medical assessment if fatigue is accompanied by any of the following
These symptoms alongside persistent fatigue warrant prompt clinical evaluation rather than a wait and see approach.
Fatigue is common. That does not mean it is normal.
The Wave Functional Health Approach
At Wave Functional Health on the Gold Coast, we assess fatigue by looking at the whole person. That includes sleep, nutrition, movement, nervous system function, blood chemistry, gut health, hormones, inflammation, mitochondrial function, stress load, and recovery capacity. We use tools including HRV analysis, InBody 580 body composition assessment, DUTCH hormone testing, GI MAP stool analysis, and functional pathology interpreted against optimal ranges rather than just flagging clinical deficiency.
The goal is not to stimulate the body into temporary energy. The goal is to rebuild the systems that allow energy to be produced properly in the first place.
If you are tired of being told everything is normal while you still feel exhausted, it may be time to investigate fatigue more deeply.
The Wave Functional Health Approach to Fatigue
At Wave Functional Health on the Gold Coast, we assess fatigue by looking at the whole person — sleep, nutrition, movement, nervous system function, blood chemistry, gut health, hormones, inflammation, mitochondrial function, stress load, and recovery capacity.
The goal is not to stimulate the body into temporary energy. The goal is to rebuild the systems that allow energy to be produced properly in the first place. If you are tired of being told everything is normal while you still feel exhausted, it may be time to investigate fatigue more deeply.
References
Ridsdale L, et al. The differential diagnosis of tiredness: a systematic review. BMC Primary Care. 2016. bmcprimcare.biomedcentral.com
Centers for Disease Control and Prevention. About Sleep. cdc.gov/sleep
Nowak A, et al. Effect of vitamin D3 on self-perceived fatigue: a double-blind randomised placebo-controlled trial. PMC5207540.
Global prevalence of long COVID, its subtypes, and risk factors: an updated systematic review and meta-analysis. PubMed. 2024. PMID 41018705.
NICE. Myalgic encephalomyelitis/chronic fatigue syndrome: diagnosis and management. NCBI Bookshelf NBK579533.
Mercola J. Your Guide to Cellular Health: Unlocking the Science of Longevity and Joy. 2024.
Myhill S, Booth NE, McLaren-Howard J. Chronic fatigue syndrome and mitochondrial dysfunction. Int J Clin Exp Med. 2009. PMC2680051.
Hwang P, et al. Mitochondrial dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome. Am J Physiol. 2025. PMC12151296.
Tardy AL, et al. Vitamins and minerals for energy, fatigue and cognition: a narrative review of the biochemical and clinical evidence. Nutrients. 2020;12(1):228.
The Lancet. Hypothyroidism. 2024. doi:10.1016/S0140-6736(24)01614-3.
Mazza AD. Personalized approaches to hypothyroidism: the role of triiodothyronine (T3) in thyroid hormone replacement. Cureus. 2025. PMC12370163.
Zhang Y, Wang L. Research progress in CFS treatment through interventions targeting the HPA axis. Frontiers in Endocrinology. 2024;15:1373748.
Tomas C, Newton J, Watson S. A review of HPA axis function in chronic fatigue syndrome. Nature Reviews Endocrinology. 2012.
Dmytriv TR, et al. Intestinal barrier permeability: the influence of gut microbiota, nutrition, and exercise. Frontiers in Physiology. 2024;15:1380713.
Di Vincenzo F, et al. Gut microbiota, intestinal permeability, and systemic inflammation: a narrative review. Internal and Emergency Medicine. 2024. PMC10954893.
Ring M, et al. An integrative approach to HPA axis dysfunction: from recognition to recovery. The American Journal of Medicine. 2025. doi:10.1016/S0002-9343(25)00353-5.
This article is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare practitioner before making changes to your health protocols.