You sleep enough but still feel tired. You wake up in the morning already short of energy. After working for a while, you just want to lie down again.
Fatigue sometimes comes from nothing more than lack of sleep, stress, irregular eating or an overloaded daily schedule. But if it goes on for several weeks, does not improve, or begins to affect your studies, work and daily life, you should look for the cause rather than simply trying to sleep more.
Anaemia, thyroid disorders, abnormal blood sugar, a shortage of certain vitamins or problems with sleep can all be linked to a lasting feeling of fatigue.
7 health checks to consider when you are often tired
1. Check the quality of your sleep
Before thinking about a whole series of tests, take another look at your sleep.
You may sleep a full 7–8 hours and still have poor sleep quality if you:
- Often wake up in the middle of the night
- Snore loudly
- Feel as though you are choking while asleep
- Still feel very tired when you wake up
- Feel very sleepy during the day
- Find it hard to concentrate
Snoring with pauses in breathing, gasping or marked daytime sleepiness may suggest sleep apnoea and needs further assessment.
2. Complete blood count – CBC
This is usually one of the basic tests considered when looking for the cause of fatigue.
A CBC checks components such as:
- Red blood cells – RBC
- Haemoglobin – Hb/HGB
- Haematocrit – HCT
- White blood cells – WBC
- Platelets – PLT
Low haemoglobin or low red blood cells may suggest anaemia. However, an abnormal result does not automatically tell you what the cause is.
3. Ferritin and iron indices
A normal CBC does not necessarily rule out iron deficiency in its early stages.
Depending on the case, your doctor may consider also checking ferritin or other tests that assess iron status.
This is particularly worth noting if you:
- Have heavy periods
- Eat a diet low in iron
- Donate blood regularly
- Are pregnant
- Have a history of iron-deficiency anaemia
- Feel tired along with dizziness or pale skin
Prolonged iron deficiency can lead to anaemia and cause fatigue, dizziness or breathlessness.
4. Thyroid check – TSH
The thyroid affects the way the body uses energy.
When the thyroid is underactive, you may experience:
- Fatigue
- Feeling the cold easily
- Weight gain
- Dry skin
- Constipation
- Dry or thinning hair
- Changes in your menstrual cycle
TSH is usually one of the first tests used to assess thyroid function. Depending on the result, your doctor may also check T4 or other tests.
5. Blood sugar and HbA1c
Abnormal blood sugar can also leave you feeling short of energy.
If your fatigue comes with:
- Excessive thirst
- Passing urine frequently
- Feeling hungry often
- Unintentional weight loss
- Blurred vision
you should talk to your doctor about having your blood sugar checked.
HbA1c shows your average blood sugar level over the past 2–3 months and is used to help detect prediabetes or diabetes.
6. Vitamin B12 and folate
Vitamin B12 and folate take part in the making of blood cells.
A B12 deficiency can be linked to anaemia and to certain neurological symptoms. A B12 or folate test is usually considered when the symptoms or earlier tests suggest a deficiency, rather than being something everyone needs to have done.
You should mention it to your doctor if your fatigue is persistent and you also have:
- Numbness or tingling in the hands and feet
- A diet that limits animal foods
- A history of B12 deficiency
- Certain digestive conditions
- Long-term use of certain medicines
7. Liver and kidney function
The liver and kidneys take part in many metabolic processes and in clearing waste from the body.
In some cases of prolonged fatigue, your doctor may consider:
Kidney function
- Creatinine
- eGFR
- Certain urine tests where appropriate
Liver function
- AST
- ALT
- GGT
- Bilirubin
- Albumin
Fatigue and weakness can occur in some liver or kidney conditions, but these tests should not be interpreted in isolation. The results need to be viewed alongside your symptoms and health history.
Do you need to have all 7 checks?
No.
This is the most important point of all.
Someone who repeatedly stays up late and sleeps 4–5 hours a day needs a different assessment from someone who sleeps enough yet feels tired, looks pale and has heavy periods.
Likewise, someone who is tired and also thirsty and passing a lot of urine will be investigated differently from someone who is tired and also gaining weight, feeling the cold easily and constipated.
So the aim is not “the more tests, the more reassurance” but to choose the right checks based on your symptoms and risk factors.
Before having tests, ask yourself 5 questions
- How long have I been tired?
- Am I really sleeping enough, and sleeping well?
- Has my weight changed recently?
- Do I have any other symptoms, such as dizziness, breathlessness, thirst, numbness in the hands and feet or feeling the cold easily?
- What medicines or supplements am I taking?
This information can sometimes point your doctor towards the cause faster than working through a long list of tests.
When should you see a doctor?
According to the NHS, you should see a doctor if fatigue lasts for several weeks with no clear cause, affects your daily life or appears alongside other symptoms.
In particular, do not simply try to “catch up on sleep” if the fatigue keeps getting worse or keeps coming back.
Track your health on Halza
If you have had tests or health check-ups several times, keeping a record of the results makes it easier to spot changes over time.
Through Halza, you can:
- Store test results and health records
- Look back at information from previous visits
- Track health indicators over time
- Look up and book appointments and tests at partner hospitals and clinics
Fatigue is not always a sign of illness. But if your body keeps telling you that you are “out of battery”, do not simply get used to the feeling — find out where it is coming from.
The information in this article is for reference only and does not replace the advice, diagnosis or instructions of a doctor. Tests should be chosen on the basis of each person's symptoms, history and state of health.
Frequently asked questions
How long should fatigue last before you see a doctor?
You should consider seeing a doctor if the fatigue lasts for several weeks with no clear cause, does not improve after rest or affects your everyday life.
If it comes with unintentional weight loss, changes in mood or frequent loud snoring and interrupted breathing during sleep, there is all the more reason to talk to your doctor.
Is fatigue caused by anaemia?
It can be, but fatigue does not always mean anaemia.
Iron-deficiency anaemia can cause fatigue, dizziness, pale skin or breathlessness. However, fatigue has a great many other causes, so your other symptoms and test results need to be considered as well.
Is a general blood test on its own enough?
Not necessarily.
A blood test can help identify some causes, but your doctor will still need to ask about your sleep, diet, stress, the medicines you are taking, your menstrual cycle, underlying conditions and any other symptoms.
References
- NHS – Tiredness and Fatigue
- NHS – Sleep Apnoea
- MedlinePlus – Complete Blood Count (CBC)
- NHLBI – Iron-Deficiency Anemia
- NIDDK – Thyroid Tests & Hypothyroidism
- CDC – A1C Test & Diabetes Symptoms
- MedlinePlus – Vitamin B Test & Liver Function Tests
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