Fatigue that does not go away with rest and lasts for weeks is not a disease in itself but a symptom. Sleep routine, nutrition, anaemia, how the thyroid gland is working, blood sugar levels and the medicines being taken are all considered together when this symptom is assessed. The cause is determined through examination and, where necessary, laboratory assessment.
Fatigue is one of the most common reasons for seeking outpatient care; yet precisely because it is so common, it is often dismissed. Thinking “everyone is tired” can delay a visit to the physician, when there may be an underlying cause that needs assessment.
Does your fatigue go away with rest? Fatigue that follows a busy week and eases over the weekend is usual; waking up tired in the morning despite having had enough sleep is a different picture, and it is the one that needs assessment.
What is assessed in long-standing fatigue?
Which of these are necessary in your case is determined according to your complaint and the examination findings.
Anaemia and iron status. Anaemia is one of the most frequently assessed causes of fatigue. The World Health Organization (opens in a new tab) reports that anaemia affects 30% of women aged 15–49, and that iron deficiency is the leading nutrition-related cause. The same source lists fatigue among the typical symptoms of anaemia; dizziness and shortness of breath, particularly on exertion, may also accompany this clinical picture. A full blood count and iron, ferritin and B12 levels are used in the assessment.
How the thyroid gland is working. Thyroid hormone levels running lower than expected may be seen alongside fatigue, feeling cold, dry skin and weight change. The assessment is made with thyroid function tests.
Blood sugar levels. Blood sugar that runs high may cause frequent urination and excessive thirst alongside fatigue. According to the World Health Organization (opens in a new tab), as of 2022 there were 830 million people living with diabetes worldwide, and 59% of adults aged 30 and over living with diabetes were not taking medication for it that year. In other words, the likelihood of going undiagnosed is high.
Sleep routine and quality. Sleep duration that appears adequate does not mean the sleep is of good quality. Snoring, frequent waking at night and daytime drowsiness are asked about separately.
Current medication and supplements. Some medicines may cause fatigue. For this reason, all the medicines and supplements you take are reviewed during the examination.
Eating routine and the intervals between meals. Long periods without food and irregular meals may contribute to fluctuations in energy during the day.
In which patients is it assessed differently?
In the situations below, a complaint of fatigue is addressed in a different order and with greater care:
- In patients who are pregnant or breastfeeding (because iron and vitamin requirements change, the assessment is made separately)
- In patients with heavy menstrual bleeding (blood loss is asked about separately)
- In patients over 65 (the use of more than one medicine and co-existing conditions are considered together)
- In patients with known kidney, liver or heart disease (the assessment is carried out alongside those diagnoses)
- In patients receiving active oncology treatment (follow-up lies with the relevant specialty)
- In patients who have recently had an operation or recovered from a severe infection (the recovery period is taken into account)
- In patients under 18 years of age (assessment lies within the field of paediatrics; this content has been prepared for adults)
How does the assessment proceed?
- Medical history. When the fatigue began, how it varies during the day, whether it changes with rest and any accompanying symptoms are recorded. Sleep, nutrition, activity routine and current medication are asked about in the same consultation.
- Physical examination. Blood pressure, pulse, height and weight measurements and a systemic examination are carried out.
- Laboratory assessment. Investigations are requested according to the complaint. The same list is not applied to everyone; what is needed varies from person to person.
- Assessing the results together. The findings are considered not one by one but in relation to one another, and the plan is drawn up together.
Points to be aware of
Do not start supplements on your own. Starting an iron or vitamin supplement on your own initiative because of fatigue may delay recognition of the underlying cause. An iron supplement provides no benefit when taken without a demonstrated iron deficiency, and in some situations it is not appropriate.
A single test result is not assessed on its own. Values take on meaning together with the complaint and the examination findings. Laboratory reference values may differ from one institution to another.
The cause of fatigue is not always a single factor. Irregular sleep and iron deficiency may be present together in the same person. For this reason they are considered together rather than separately.
Results vary from person to person. The time taken to determine the cause and the path to be followed are not the same in every patient.
When should you see a physician without delay?
If you notice these symptoms, consult a physician without delay:
- Fatigue that has reached a level that disrupts everyday activities
- Unintentional and unexplained weight loss
- Fever and night sweats accompanying the fatigue
- Shortness of breath that worsens over days
- Marked pallor of the skin
- Frequent urination and excessive thirst
- A marked increase in menstrual bleeding
In the event of chest pain, sudden shortness of breath, sudden loss of strength, disturbance of speech or altered consciousness, go directly to the emergency department.
Frequently asked questions
Which tests are requested for fatigue?
No standard list is applied. According to your complaint and the examination findings, a full blood count, iron and ferritin, B12, thyroid function tests and blood sugar are generally assessed. Which of them are needed is determined at the end of the examination. If you have results from the past year, bringing them prevents unnecessary repetition.
My tests came back normal but my fatigue continues; what should I do?
This is not uncommon. Sleep quality, meal routine, activity habits and the burden of stress are assessed separately. In addition, some areas may not have been included in the first set of investigations. If the complaint continues, it is advised that a follow-up appointment is made and the assessment is reviewed again.
Would it be all right for me to start taking an iron supplement?
Starting one without an assessment by a physician is not advised. An iron supplement is appropriate only when a deficiency has been demonstrated; used unnecessarily, it provides no benefit, and for some people it is unsuitable. Tell your physician about every supplement you take.
Is fatigue a symptom of thyroid disease?
Fatigue is one of the symptoms that may be seen in thyroid disease, but on its own it does not establish a diagnosis. Thyroid assessment is made with blood tests and examination. If swelling in the neck, hoarseness or difficulty swallowing accompanies it, this is assessed separately.
How many weeks of fatigue call for assessment?
No specific time threshold has been defined. The generally accepted approach is to assess fatigue that does not go away with rest and has lasted for several weeks. If weight loss, fever or shortness of breath accompanies it, it is advised that a physician is consulted without waiting for that period to pass.
What should I prepare before going to a consultation?
Bring a list of all the medicines and supplements you take, your test results from the past year and, if you have them, your discharge summaries. Noting down your sleep hours and how your fatigue varies during the day for a few days also contributes to the assessment.
Sources
- World Health Organization, Anaemia fact sheet, 10 February 2025. https://www.who.int/news-room/fact-sheets/detail/anaemia (opens in a new tab)
- World Health Organization, Diabetes fact sheet, 14 November 2024. https://www.who.int/news-room/fact-sheets/detail/diabetes (opens in a new tab)
