Why Am I Always Tired? 11 Causes I See Every Week as an General Practitioner

"I'm just so tired all the time."

I hear that sentence most days I am on the floor. It is so common in general practice that we have an abbreviation for it in our notes: TATT. Research from the British Journal of General Practice found that over 10% of patients attending primary care describe at least one month of substantial fatigue, and my own appointment book backs that up.

Here is the uncomfortable truth I want to open with. When I order blood tests for tiredness, most of them come back normal. An Australian study of general practice records reviewed 342 patients presenting with tiredness and found that only 3% ended up with a significant clinical diagnosis based on their pathology results. That statistic is not a reason to skip the blood test. It is a reason to stop treating the blood test as the whole consultation.

Because in my experience, persistent fatigue is almost never one thing. It is usually three or four small things stacked on top of each other, and the stack is what breaks you.

Below are the eleven causes I find most often, roughly in the order I think about them. I have written this for patients, not for colleagues, so I have explained the medical terms as I go.

First, a distinction that changes the entire consultation

Before the list, I need you to answer one question, because your answer sends me down completely different diagnostic paths.

Are you sleepy, or are you fatigued?

Sleepiness means you would fall asleep if you sat still in a quiet room. You nod off in front of the TV at 8pm, or on the train, or at traffic lights. Sleepiness points me toward your sleep: quantity, quality, or a sleep disorder.

Fatigue means you feel flattened, heavy and depleted, but you could not nap if you tried. Your body is exhausted and your brain will not switch off. Fatigue points me toward mood, medications, metabolic causes, and inflammation.

Exertional intolerance is a third category. You feel reasonable at rest, but a short walk or a shopping trip wipes you out for the rest of the day, or the next two days. This is the one I take most seriously.

When patients tell me "tired", they could mean any of the three. Getting specific in the first ninety seconds saves us both months.

1. You are not giving yourself enough opportunity to sleep

This is the least glamorous answer and by far the most common one.

There is a difference between sleep duration (how long you actually slept) and sleep opportunity (how many hours you were horizontal with your eyes shut and the lights off). Most of the tired people I see have a sleep opportunity problem, not a sleep disorder. They are in bed for six and a half hours and expect eight hours of sleep to come out the other end.

The national picture is not pretty. The 2016 Sleep Health Foundation survey of 1,011 Australian adults found that inadequate sleep, in either duration or quality, affects 33% to 45% of adults, with 12% sleeping under five and a half hours a night. The authors put it bluntly: "Sleep problems and daytime consequences are endemic among Australian adults." The Deloitte Access Economics report commissioned by the Sleep Health Foundation estimated that 39.8% of Australian adults experience some form of inadequate sleep, with $40.1 billion in lost wellbeing attached to it.

More recent Flinders University work found nearly a third of Australian adults sleep less than the recommended seven hours, with young adults worst affected. Associate Professor Nicole Lovato noted that for that group, "poor sleep is negatively impacting their productivity".

What I ask: What time do the lights actually go off, and what time does the alarm go off? Count it on your fingers. If the number starts with a six, we have found at least part of your answer.

2. Obstructive sleep apnoea, especially if you snore

Obstructive sleep apnoea (OSA) is when the upper airway repeatedly collapses during sleep. Each collapse drops your blood oxygen and triggers a micro-arousal, a brief surfacing out of deep sleep that you never remember. You can have hundreds of these a night. You will swear you slept eight hours. Your brain got nothing like eight hours of restorative sleep.

A Western Australian population study estimated that moderate to severe OSA affects 9.1% of adults, rising to 12.4% of men, and concluded that undiagnosed OSA is highly prevalent in the general community. Meanwhile, AIHW data shows only about 6.7 per 1,000 Australian adults had a diagnostic sleep study in 2019. The gap between how many people have it and how many people have been tested for it is enormous.

The classic picture is a middle-aged man with a thick neck who snores like a chainsaw. That picture is doing real harm, because women with OSA frequently present with fatigue, low mood and insomnia rather than loud snoring and obvious daytime sleepiness.

What I look for: witnessed pauses in breathing, waking with a dry mouth or headache, nocturia (getting up to urinate more than once overnight), treatment-resistant high blood pressure, and an Epworth Sleepiness Scale score of 11 or more. If that pattern fits, I arrange a sleep study. Home-based studies are now the norm and are far less of an ordeal than most people fear.

3. Insomnia disorder, which is not the same as being a bad sleeper

Chronic insomnia is not simply a shortage of sleep. It is a state of hyperarousal, where the nervous system stays on alert around the clock. That is why people with insomnia are exhausted yet cannot nap. Between 10% and 30% of Australian adults report chronic difficulty falling or staying asleep with daytime consequences.

Here is where I want to be very direct with you. Sleeping tablets are not the answer for chronic insomnia, and the evidence on this is not close. Australian and international guidelines recommend "cognitive behavioural therapy for insomnia (CBT-i) as the first-line treatment", as set out in the Australian Journal of General Practice. The Sleep Health Foundation notes that CBT-i improves insomnia symptoms in up to 80% of people, and that around 90% of those people reduce or stop their sleep medication.

CBT-i usually runs over four to eight sessions and includes sleep restriction therapy and stimulus control, which sound harsh and work remarkably well. In Australia you can access it through a psychologist under a GP Mental Health Treatment Plan, or through validated digital programs. Ask me for a referral. Please do not ask me for temazepam.

4. Low iron stores, even when your haemoglobin is perfectly normal

This is the one I catch most often, and the one most frequently missed elsewhere.

You can be iron deficient without being anaemic. Serum ferritin measures your iron stores, and it falls long before your haemoglobin does. By the time you are anaemic, you have been running on empty for months. According to the Medical Journal of Australia, 22.3% of Australian women have depleted iron stores (ferritin below 30 micrograms per litre), compared with 3.5% of men. A population study of young Australian women aged 18 to 39 found the prevalence of ferritin below 30 was 34.8%. More than one in three.

Iron deficiency causes fatigue, brain fog, hair shedding, cold intolerance, breathlessness on stairs, and restless legs at night. It is also a cause with a genuinely satisfying fix.

A UK audit of 16,889 primary care requests for tiredness found something that should embarrass all of us: ferritin was only requested in 9.4% of cases, yet 26% of the ferritin results that were ordered came back abnormal. It was one of the lowest-ordered tests with one of the highest yields.

What I do: I check full blood count and ferritin, plus iron studies including transferrin saturation if the picture is unclear. If ferritin is low, I do not just hand over tablets and wave you off. I ask why. Heavy menstrual bleeding, coeliac disease, poor dietary intake and gastrointestinal blood loss all need consideration, and in anyone over 50 with unexplained iron deficiency, bowel investigation is not optional.

5. Your mood is doing more of the work than you realise

Fatigue is one of the core somatic symptoms of depression, and it is often the only one people bring to the appointment. Anxiety does the same thing through a different mechanism: sustained sympathetic nervous system activation is metabolically expensive, and living in that state for months is exhausting.

The ABS National Study of Mental Health and Wellbeing found 21.5% of Australians aged 16 to 85 had a 12-month mental disorder, with anxiety disorders the most common group at 17.2%. Among 16 to 24 year olds, the figure was 38.8%. Fewer than half of those with a 12-month disorder sought professional help.

I am not suggesting your tiredness is "all in your head". I am telling you that mood and energy run on overlapping circuitry, and that ignoring one while investigating the other wastes everyone's time.

What I ask about: anhedonia (loss of pleasure in things you used to enjoy), early morning waking, irritability, concentration, and whether the tiredness lifts on holidays. Burnout in particular tends to improve away from work and return within two days of going back. That pattern tells me a lot.

6. Thyroid, blood sugar and other metabolic causes

Hypothyroidism (an underactive thyroid) slows metabolism across every organ system and produces fatigue, cold intolerance, constipation, weight gain and dry skin. It is easy to test with a TSH (thyroid stimulating hormone) level and easy to treat.

Undiagnosed type 2 diabetes causes fatigue through poor glucose utilisation and disturbed sleep from nocturia. I check an HbA1c, which reflects average blood glucose over roughly three months.

I also consider chronic kidney disease, liver disease, vitamin B12 and vitamin D deficiency, coeliac disease, and less commonly haemochromatosis, which is genuinely common in Australians of northern European ancestry and causes fatigue through iron overload rather than deficiency.

These conditions are individually uncommon as a cause of tiredness. Collectively they are worth a single blood test.

7. Coeliac disease, which hides in plain sight

Coeliac disease is an autoimmune reaction to gluten that damages the small intestine and impairs nutrient absorption. Most Australians think of it as a bowel condition. Fatigue is frequently the presenting symptom, often driven by malabsorption of iron, folate and B12.

Coeliac Australia estimates that 1 in 70 Australians have coeliac disease and that only around 20% are diagnosed. A Western Australian population study drawing on the Busselton Health Study concluded that the prevalence in an Australian rural community is high and that "Most patients are undiagnosed, and asymptomatic."

One critical warning. The screening test, tissue transglutaminase IgA, only works if you are eating gluten. If you have already cut gluten out because it made you feel better, the test will very likely be falsely negative and we will have lost our chance at a clean diagnosis. Talk to me before you change your diet, not after.

8. Post-viral fatigue and long COVID

This has reshaped my caseload over the past few years. An Australian stratified random survey published in the MJA found that at a mean of 12.6 months after infection, 39.1% of people who had COVID-19 reported at least one persistent new symptom, and 14.2% met criteria for clinical long COVID. The most commonly reported symptoms were fatigue, impaired neurocognition (brain fog and word-finding difficulty), breathlessness on exertion and disturbed sleep.

Post-viral fatigue is not limited to COVID. Epstein-Barr virus, influenza, Ross River virus and Q fever all do it, and Ross River in particular is one we see regularly in parts of Australia.

The feature I look for is post-exertional malaise (PEM), a disproportionate crash in symptoms 12 to 48 hours after physical or cognitive effort. If PEM is present, my advice reverses completely. I stop encouraging graded exercise and start teaching pacing, which means working within an energy envelope rather than repeatedly pushing through and crashing. Getting this distinction wrong makes people worse, and I have seen it happen.

9. Your medication list

I go through every box, every patch and every supplement, because this is a genuinely common and completely reversible cause.

The usual offenders in my practice: sedating antihistamines, beta blockers, opioids, gabapentinoids such as pregabalin, some antidepressants, antipsychotics, muscle relaxants, and anything with a high anticholinergic burden, which is a cumulative measure of how many of your medications block acetylcholine and cause sedation and cognitive fog.

Bring everything to the appointment, including the melatonin gummies and the magnesium. A medication review costs nothing and occasionally solves the whole problem in one visit.

10. Caffeine and alcohol, which are working against you in opposite directions

Caffeine blocks adenosine receptors. Adenosine is the molecule that builds up across your waking hours and creates sleep pressure, so caffeine does not give you energy, it masks your tiredness. Its half-life is roughly five to six hours, meaning a 3pm long black still has meaningful caffeine circulating at 9pm.

A controlled study published in the Journal of Clinical Sleep Medicine gave participants 400mg of caffeine, about two to three cups of coffee, at zero, three and six hours before bed. All three timings significantly disrupted sleep. The authors reported that "Even at six hours, caffeine reduced sleep by more than one hour" (Drake et al., 2013). The American Academy of Sleep Medicine's recommendation that followed was to keep caffeine before 5pm.

Alcohol is the mirror image. It is sedating, so it gets you to sleep faster, then it fragments the second half of the night and suppresses REM sleep. This is why a few wines can produce eight hours in bed and the energy of five.

What I suggest: a hard caffeine cut-off eight hours before bed for two weeks, and three to four consecutive alcohol-free nights. Two weeks is enough to tell the difference.

11. Deconditioning, which feels exactly like illness

This is counterintuitive and I lose people at this point, so stay with me.

When you are exhausted, you move less. When you move less, your cardiorespiratory fitness declines, your muscles lose oxidative capacity, and ordinary activity starts to require a greater share of your maximum effort. Climbing the stairs now feels genuinely hard, because for your current physiology it genuinely is. That is deconditioning, and it feels indistinguishable from disease.

A 2023 systematic review and meta-analysis of 38 randomised controlled trials found that physical activity interventions moderately reduced perceived fatigue, with a standardised mean difference of 0.70. Notably, benefits appeared in interventions as short as two to six weeks.

Even more useful for tired people: a randomised controlled trial in sedentary adults with persistent fatigue found that six weeks of low-intensity exercise outperformed moderate-intensity exercise for reducing fatigue symptoms, and the improvements were unrelated to changes in aerobic fitness. You do not need to get fit to feel less tired. You need to move gently and consistently.

The single exception is the one I flagged above. If you have post-exertional malaise, this advice does not apply to you.

What I actually do in the appointment

If you book in with me for fatigue, expect this:

A long history. Sleep timing, snoring, mood, stress, weight change, bowel habit, menstrual history, alcohol, caffeine, medications, recent infections, and what a bad day looks like compared with a good one.
An examination. Blood pressure, weight, thyroid, lymph nodes, abdomen, and a look at your conjunctivae and nail beds.
Targeted blood tests. Typically full blood count, ferritin and iron studies, TSH, HbA1c, urea and electrolytes, liver function tests, C-reactive protein, coeliac serology, vitamin B12, folate and vitamin D.
A plan for the negative result. This matters more than the tests. Normal bloods are useful information, not a dead end, and we will have a next step ready.
A follow-up appointment. Fatigue is not a single-consultation problem, and a long appointment booked in advance serves you far better than a rushed one.

The symptoms that make me want to see you sooner

Book urgently, and say why when you call, if your tiredness comes with any of the following:

Unintentional weight loss
Drenching night sweats or persistent fevers
New or enlarging lumps and lymph nodes
Blood in your stool, black stools, or a persistent change in bowel habit
Shortness of breath at rest, chest pain, or fainting
New severe headache or any new neurological symptom
Thoughts of harming yourself

What I want you to take away

Tiredness is a symptom, not a diagnosis, and it deserves more than a shrug and a blood test. In my practice, the most common answers are unglamorous: not enough hours in bed, an untreated sleep disorder, low iron, low mood, and a caffeine habit that is quietly eating the back end of the night.

The good news is that most of those are fixable, and several are fixable quickly. What rarely works is waiting it out, self-diagnosing from a search results page, or accepting "your bloods are normal" as the end of the conversation.

If you have been tired for more than a month, book a long appointment. Bring your medications, and be ready to tell me the time your lights actually go off.

This article is general information based on current evidence and my clinical experience in Australian general practice. It is not a substitute for individual medical advice. If you are struggling with your mental health, please speak with your GP, or contact Lifeline on 13 11 14 or Beyond Blue on 1300 22 4636.

References and further reading

Adams RJ, et al. Sleep health of Australian adults in 2016: results of the Sleep Health Foundation national survey. Sleep Health, 2017.
Sleep Health Foundation and Deloitte Access Economics. Asleep on the Job: Costs of Inadequate Sleep in Australia.
Flinders University. 1 in 3 young adults not getting enough sleep, 2026.
Simpson L, et al. High prevalence of undiagnosed obstructive sleep apnoea in the general population. Sleep and Breathing, 2013.
Australian Institute of Health and Welfare. Sleep-related breathing disorders with a focus on obstructive sleep apnoea, 2021.
Sweetman A, et al. General practitioner assessment and management of insomnia in adults. Australian Journal of General Practice, 2023.
Sleep Health Foundation. Cognitive Behavioural Therapy for Insomnia (CBT-I).
Updating the diagnosis and management of iron deficiency in the era of routine ferritin testing. Medical Journal of Australia, 2024.
Iron insufficiency among young Australian women: a population-based survey. Internal Medicine Journal, 2019.
Handjiev S, et al. 'Tired all the time': an audit against NICE guidance on investigation of fatigue. Annals of Clinical Biochemistry, 2025.
Gialamas A, et al. Investigating tiredness in Australian general practice. RACGP.
Australian Bureau of Statistics. National Study of Mental Health and Wellbeing, 2020-2022.
Coeliac Australia. About coeliac disease.
Hovell CJ, et al. High prevalence of coeliac disease in a population-based study from Western Australia. MJA, 2001.
Persistent symptoms after COVID-19: an Australian stratified random health survey on long COVID. MJA, 2024.
Drake C, et al. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine, 2013.
Barakou I, et al. Effectiveness of physical activity interventions on reducing perceived fatigue. Scientific Reports, 2023.
Puetz TW, Flowers SS, O'Connor PJ. Aerobic exercise training and feelings of energy and fatigue in sedentary young adults with persistent fatigue. Psychotherapy and Psychosomatics, 2008.
Tired all the time: can new research on fatigue help clinicians? British Journal of General Practice, 2009.