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Dr. Chrysoula I. Liakou MD, PhD
- Treated online: Yes, for assessment and a treatment plan; blood tests are arranged at a laboratory near you and reviewed at a follow-up consultation.
- What it is: persistent tiredness or lack of energy that rest does not relieve; fatigue lasting more than 4 weeks despite reasonable sleep deserves assessment, and it is never just laziness.
- Commonest causes: too little or broken sleep, stress, depression and anxiety, iron deficiency, an underactive thyroid, low vitamin B12, diabetes, sleep apnoea, alcohol and medicines such as antihistamines and some antidepressants.
- Blood tests: a first panel checks full blood count, ferritin (iron stores), thyroid function, vitamin B12 and folate, HbA1c (blood sugar) and kidney and liver function; normal results are useful too, because they move the focus to sleep and mood.
- Post-viral fatigue: common after flu, COVID-19 or glandular fever and usually settles within 4 to 12 weeks with pacing rather than pushing; fatigue persisting beyond 3 months with marked worsening after activity needs assessment for ME/CFS.
- Emergency: call 112 for someone who is increasingly drowsy or confused or cannot be woken properly, or for tiredness with chest pain or severe breathlessness.
Tiredness with unexplained weight loss, drenching night sweats, fevers, new lumps, breathlessness or chest pain needs prompt in-person assessment rather than an online booking. Someone who is becoming drowsy and confused, or cannot be woken properly, is an emergency: call 112. For everything slower and quieter, which is most fatigue, an online doctor is a good place to start.
Can an online doctor help with fatigue?
Constant tiredness, or lethargy, usually has ordinary, findable causes: too little or broken sleep, stress, low mood or anxiety, iron deficiency and anaemia, an underactive thyroid, low vitamin B12, diabetes, medicines (including antihistamines and some antidepressants) and alcohol. Fatigue lasting more than a few weeks despite reasonable sleep deserves a medical assessment and simple blood tests; results vary person to person, so testing beats guessing.[1]
How an online consultation helps with fatigue
- A structured search for the cause: "Tired all the time" has a differential diagnosis like anything else. The doctor works it methodically: sleep, mood, body, medicines, life load, and does not stop at "try to rest more".
- The right blood tests, directed: Where the story warrants it, the doctor directs a focused panel near you: full blood count, ferritin, thyroid function, B12 and folate, blood sugar, and reviews the results with you at follow-up.[1]
- A proper medication review: Prescriptions, pharmacy medicines and supplements all get looked at, because sedating antihistamines, beta-blockers and even the timing of doses are classic quiet causes.
- Sleep and mood taken seriously: The two biggest causes of persistent tiredness get real assessment, not a leaflet, with treatment plans and follow-up built in.
What blood tests are done for fatigue?
The usual first panel checks a full blood count for anaemia, ferritin for iron stores, thyroid function, vitamin B12 and folate, blood sugar (HbA1c) for diabetes, and kidney and liver function; a coeliac test is sometimes added when digestive symptoms fit.[1] Normal results are genuinely useful too: they close the medical trapdoors and move attention to sleep, mood and pacing, which cause most persistent tiredness.
What causes constant tiredness?
Sleep, in quantity and quality
The obvious cause still deserves an honest audit: hours in bed, hours asleep, and what the phone was doing at 1 a.m. Chronic insomnia is its own treatable condition, not a character trait. Quality matters as much as quantity: loud snoring, witnessed pauses in breathing, morning headaches and waking unrefreshed point to sleep apnoea, which needs a sleep-clinic referral, and which makes daytime sleepiness dangerous behind the wheel; say so honestly, because your doctor will. Shift work, small children and revenge bedtime scrolling all belong in the audit too, without judgement.
Mood and load
Depression is one of the most common causes of persistent exhaustion, and its tiredness has a signature: flat rather than sleepy, worse in the morning, with joy drained out of things you used to like.[5] Anxiety exhausts by keeping the engine revving all day. And plain overload, the caring-working-grieving kind of chronic stress, produces fatigue that no blood test will ever explain. These are not lesser causes; they are the most common ones, and they respond to treatment. If low mood is part of your picture, the depression page describes that assessment honestly.
The body’s quiet culprits
Iron deficiency and anaemia sit high on the list, especially with heavy periods, restricted diets or pregnancy; anaemia is among the most common conditions worldwide, and treating a proven deficiency genuinely restores energy.[2] An underactive thyroid brings tiredness with feeling cold, dry skin, constipation and weight gain. Low vitamin B12 adds pins and needles and low mood. Diabetes announces itself with thirst, frequent urination and blurring vision. Post-viral fatigue is real and common after flu, glandular fever and COVID: weeks of heaviness that lift gradually with patient pacing. Each of these is findable with the story plus the right test.
Medicines, alcohol and the home itself
Sedating antihistamines, some antidepressants, beta-blockers, strong painkillers and sleeping tablets all cause daytime tiredness, alone or in combination. Alcohol deserves its plain sentence: it sedates you to sleep, then wrecks the second half of the night, so regular evening drinking is one of the most reliable manufacturers of tired mornings. And one rare cause is worth knowing because it is reversible and missed: if several people in your household are tired, headachy and foggy at once, and feel better away from home, check your carbon monoxide alarm and have the boiler checked promptly.
When is fatigue a red flag?
Fatigue becomes a red flag in combination: with unexplained weight loss, drenching night sweats, persistent fever, new lumps, breathlessness, chest pain, unexplained bleeding, or progressive muscle weakness. Those combinations need prompt in-person examination and investigation rather than online reassurance.[3] On its own, even long-standing tiredness is usually explained by sleep, mood or a treatable deficiency; the red-flag check exists so that the exceptions are caught early.
How doctors sort tiredness: first steps
Swipe sideways to compare →
| Presentation | Likely first step | Suitable for online care? | When referral or in-person care is needed |
|---|---|---|---|
| Tired for weeks with broken sleep, stress or low mood | Online assessment of sleep and mood; treatment plan with follow-up | Usually yes | If mood deepens or thoughts of self-harm appear |
| Persistent tiredness despite reasonable sleep | Structured history plus directed blood tests (thyroid, iron, B12, HbA1c) | Yes; tests are done at a laboratory near you | Abnormal results needing examination or ongoing monitoring |
| Loud snoring, witnessed breathing pauses, sleepy days | Sleep apnoea assessment and sleep-clinic referral | Yes, for assessment and referral | Diagnosis and CPAP setup are specialist-led; do not drive while dangerously sleepy |
| Fatigue with weight loss, night sweats, fever or new lumps | Prompt in-person examination and investigations | No | Red-flag combinations need in-person care promptly[3] |
| Increasing drowsiness, confusion, or someone who cannot be woken | Emergency care | No | Call 112 now |
Not sure which row is you? A doctor can tell you in one consultation.
See available times →What the doctor checks in an online fatigue consultation
The history does most of the diagnostic work with fatigue, and history is exactly what video does well. The doctor will typically check:
- The shape of the tiredness: sleepy (dozing in front of the TV points to sleep quantity or apnoea), weary (flat and joyless points to mood), or weak (true loss of muscle power points to the body and needs examination). The words you choose genuinely steer the work-up.
- The sleep story, honestly: bedtime, waking, snoring, pauses, restless legs, shifts, children, and screens.
- Mood screening: brief, structured questions for depression and anxiety, because they are the most common causes found.[5]
- Periods and diet: heavy periods are a leading route to iron deficiency; restricted and vegan diets raise the B12 question.
- Everything you take: prescriptions, pharmacy medicines, supplements, alcohol, caffeine and anything bought online.
- Recent illness: flu, glandular fever, COVID and other infections, because post-viral fatigue changes the plan to pacing rather than pushing.
- The red-flag sweep: weight, sweats, fevers, lumps, breathlessness, bleeding, asked every time.
- The load you are carrying: work, caring, grief, finances; fatigue is sometimes the body keeping honest accounts.
One limit is stated plainly: a video call cannot examine you or run tests. What it can do is decide which tests you actually need and make sure they happen, which is precisely where tired people usually get stuck.
Treatment options for fatigue and tiredness
What you can do yourself
Anchor your wake time seven days a week; a steady anchor does more than any early night. Get daylight and movement most days, because activity, built up gradually, treats most fatigue better than rest does, with one exception worth knowing: after viral illness, pace rather than push, and let good weeks raise the ceiling slowly. Keep caffeine before mid-afternoon and be honest about alcohol’s role in tired mornings. Supplements deserve honesty too: iron and B12 help only when you are actually deficient, so test before you dose, and energy drinks are borrowed energy at high interest. If you cannot stay awake behind the wheel, do not drive; that is a symptom to report, not push through.
Prescription treatment
Treatment follows the finding. A prescription is never issued without a consultation; when tests confirm a cause, the fixes are satisfying: iron for proven deficiency with a recheck to confirm stores recover, levothyroxine for a confirmed underactive thyroid with repeat testing to steady the dose, B12 replacement, and structured care for diabetes.[1] When the cause is insomnia, the honest first-line treatment is CBT-I rather than tablets; sleeping tablets add grogginess to tiredness, are short-term options at most, and controlled hypnotics are not prescribed online. Stimulants and "energy" medicines are not prescribed online either, because they mask fatigue rather than treat it. Persistent fatigue with post-exertional crashes is assessed against the ME/CFS pathway and referred to specialist services.[4]
When fatigue is treated online, and when you need in-person care
Treated online: fatigue driven by insomnia, stress, low mood or anxiety; test-directed work-ups with results reviewed at follow-up; confirmed iron, B12 and thyroid causes, with monitoring arranged locally; post-viral fatigue with a pacing plan; and medication reviews where a medicine is the likely culprit.
In-person care: red-flag combinations (weight loss, night sweats, fever, lumps, breathlessness, bleeding) go promptly to in-person examination;[3] suspected sleep apnoea goes to a sleep clinic, with a plain warning about driving; fatigue with post-exertional malaise lasting months goes to the ME/CFS specialist pathway;[4] abnormal results needing examination go to in-person care with the paperwork done; and anyone becoming drowsy, confused or unrousable goes to 112, immediately.
When to get in-person care
Call 112 for someone who is increasingly drowsy, confused or cannot be woken properly, for tiredness with chest pain or severe breathlessness, and for a child who is floppy, drowsy and hard to rouse. If several household members feel tired, headachy and foggy at home and better away from it, treat it as possible carbon monoxide poisoning: get everyone into fresh air and seek urgent help. Book prompt in-person care, rather than online, for fatigue with weight loss, night sweats, fevers or new lumps.
If you are having thoughts of harming yourself, call 112 in an emergency. You can also find your national crisis helpline at findahelpline.com. You do not have to wait for an appointment.
How Mobi Doctor works
- Book a time that suits you: open daily 7am–11pm CET. You can see a doctor over video, usually within 15 minutes. No subscription, exact price up front.
- Speak to a licensed doctor about fatigue and tiredness: a private video call: you describe what you feel, the doctor asks what matters, and you agree the right plan together.
- Leave with a plan: tests directed near you, treatment where a cause is confirmed, and a booked follow-up to review the results together, honestly.
No sign-up needed
Tiredness can have more than one cause. Tick every symptom you have to see each condition page that mentions it. It finds the right page, not a diagnosis: a doctor gives you that on a video call.
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Frequently asked questions about fatigue and tiredness
What is fatigue, and how is it different from being tired?
Fatigue is tiredness or lack of energy that persists for weeks and is not relieved by a good night's sleep, so that ordinary tasks take an effort they did not used to. Ordinary tiredness follows a late night or a hard week and lifts with rest. Fatigue that has lasted more than four weeks despite reasonable sleep deserves a medical assessment and simple blood tests.
What does fatigue feel like?
Fatigue takes three main shapes, and the shape steers the diagnosis: sleepy (dozing off in front of the TV points to too little sleep or sleep apnoea), weary (flat, joyless and unmotivated points to low mood or stress), and weak (true loss of muscle power points to a physical cause and needs examination). Brain fog, heavy limbs and needing to rest after small tasks are common companions.
What causes constant tiredness and fatigue?
The commonest causes of fatigue are short or broken sleep, chronic stress, depression and anxiety, iron deficiency (with or without anaemia, especially with heavy periods), an underactive thyroid, low vitamin B12, diabetes, sleep apnoea, alcohol and medicines such as antihistamines, beta-blockers and some antidepressants. Perimenopause, pregnancy and recovery from a viral illness are frequent causes too, and several often overlap.
Why am I tired even after a full night's sleep?
Fatigue after a full night in bed points to the quality of sleep rather than the quantity: sleep apnoea (especially with loud snoring or witnessed pauses in breathing), alcohol in the evenings, depression, an underactive thyroid or medication effects. Waking unrefreshed for weeks is exactly the pattern the assessment untangles, and loud snoring with daytime sleepiness needs a sleep-clinic referral.
Can an online doctor order blood tests for fatigue?
Yes. After the video assessment of your fatigue, the doctor directs a focused panel (typically full blood count, ferritin, thyroid function, vitamin B12 and folate, and HbA1c) to a laboratory near you, then reviews the results with you at a follow-up appointment and treats what is found.
Which deficiencies cause tiredness?
Iron deficiency, with or without anaemia, is the commonest deficiency behind fatigue, especially in women with heavy periods. Low vitamin B12 and folate cause fatigue with pins and needles and low mood. Vitamin D is discussed often, with weaker evidence for tiredness specifically. Each is confirmed by a blood test before treatment, because taking iron you do not need can harm.
How do I fix fatigue?
Fixing fatigue starts with treating the cause the assessment finds; alongside that, anchor your wake time every day, weekends included, get daylight and movement most days (activity built up gradually treats most fatigue better than rest does), keep caffeine before mid-afternoon, be honest about alcohol, and treat low mood or stress rather than pushing through it. After a viral illness, pace rather than push.
How long does post-viral fatigue last?
Post-viral fatigue after flu, COVID-19 or glandular fever usually settles within 4 to 12 weeks, improving in steps rather than a straight line, if activity is paced and good weeks are used to raise the ceiling slowly. Fatigue that is still marked after 3 months, particularly with a clear worsening after activity, needs assessment for ME/CFS or another cause.
Is chronic fatigue syndrome the same as being tired all the time?
No. ME/CFS involves severe, persistent fatigue with post-exertional malaise, a marked worsening after activity that would previously have been normal, often with unrefreshing sleep and brain fog. It is diagnosed on the pattern over months, after other causes of fatigue are excluded, and it is managed with pacing and specialist support rather than graded exercise.
When should I worry about tiredness?
Worry about fatigue when it keeps company: weight loss you did not intend, drenching night sweats, fevers, new lumps, breathlessness, chest pain, unexplained bleeding or progressive weakness all mean prompt in-person assessment. Tiredness alone, even long-standing, is usually explained by sleep, mood or a treatable deficiency; the red-flag check exists so the exceptions are caught early.
Can perimenopause, pregnancy or older age cause fatigue?
Yes. Perimenopause causes fatigue through broken sleep, night sweats and hormonal change, and the assessment separates that from thyroid or iron problems that are common at the same age. Fatigue in pregnancy is usual in the first and third trimesters, with anaemia the main treatable cause. In older people, fatigue more often comes from medicines, heart or lung disease, low mood or poor sleep, so the review is wider.
How can I prevent fatigue coming back?
Keep the habits that fixed the fatigue: a fixed wake time, daylight and regular movement, caffeine only in the morning, alcohol within limits, meals at regular times and iron-rich food if iron was low. Re-check any deficiency after treatment, keep thyroid medication reviews, and act early on poor sleep or low mood, which are the two causes most likely to return.
- Tiredness/fatigue in adults, NICE Clinical Knowledge Summaries, revised 2024.
- Anaemia: fact sheet, WHO, World Health Organization, 2023.
- Suspected cancer: recognition and referral (NG12), NICE, National Institute for Health and Care Excellence, 2015 (updated 2023).
- Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management (NG206), NICE, National Institute for Health and Care Excellence, 2021.
- Depressive disorder (depression) fact sheet, WHO, World Health Organization, 2025.
- Tiredness and fatigue, NHS, National Health Service (UK), accessed October 2026.
This page is for information only and is not a substitute for a medical consultation. Guideline links are provided for transparency; treatment decisions are made with your doctor.
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