Constant tiredness: which tests are worth doing

Elena Kasimtseva — GP, gastroenterologist, Medical Director of GMS Clinic

Tiredness is one of the most common complaints doctors hear. It is also one that is often investigated badly: either nothing is checked at all, or a large panel of tests "for everything" is ordered.

In practice a sensible approach looks different: the doctor first considers the most likely causes and then orders a limited set of tests. The more tests are done without a specific clinical question, the higher the chance of random abnormalities that have nothing to do with how you feel.

First, not the tests

Before any laboratory tests, it is important to understand how the person sleeps, whether there is snoring and daytime sleepiness, how adequate their diet is, how much physical activity they get, what medications and supplements they take, and whether there has been a recent infection, a change in weight or significant emotional strain. Anxiety and depressive symptoms are worth assessing separately.

Chronic sleep deprivation, sleep disorders including obstructive sleep apnoea, emotional overload and medication side effects are common causes of tiredness. That is why investigation starts with the history and examination, not with as many tests as possible. International guidelines also stress that laboratory tests without specific indications have low diagnostic value.

Which tests can genuinely make sense

There is no single mandatory set for everyone with tiredness. Tests are chosen according to age, symptoms, diet, chronic conditions and the findings on examination. Most often the doctor may start with the following.

• Full blood count — AED 100. Detects anaemia and some other changes in the cellular composition of the blood.
• Ferritin — AED 210. Shows iron stores. Iron deficiency can exist before anaemia develops and cause tiredness and reduced capacity for work and exercise. Checking ferritin is especially important with heavy periods, pregnancy, a restrictive diet or possible chronic blood loss. In NICE guidelines, ferritin is among the tests that may be used when investigating persistent unexplained fatigue.
• TSH — AED 125. This is the main screening test for thyroid dysfunction in adults. If TSH is abnormal, free T4 is added, and if TSH is low, free T3 as well where needed. Testing T3, T4 and TSH all at once in every patient with tiredness is usually unnecessary.
• Glucose and/or HbA1c — fasting glucose AED 45, HbA1c AED 130. These help detect disorders of carbohydrate metabolism. HbA1c is also among the tests that may be used when investigating prolonged unexplained fatigue. Measuring insulin and calculating HOMA-IR is not routinely needed for tiredness as the only complaint.
• Basic blood biochemistry — creatinine AED 55, electrolytes (sodium, potassium, chloride) AED 100, liver function tests AED 275. Depending on the situation, it makes sense to check kidney function, electrolytes and liver function. These tests help rule out conditions that sometimes show up as general weakness and fatigue.

What about vitamin D and B12?

They do not need to be measured in everyone with tiredness.

Vitamin B12 — AED 175 — is especially important to check with a vegan or markedly restrictive diet, diseases of the stomach and small intestine, after stomach or bowel surgery, with certain autoimmune diseases, and when taking medications that can impair its absorption. NICE recommends taking into account both symptoms and risk factors for B12 deficiency.

Vitamin D — AED 250 — can be added if there are risk factors for deficiency or a matching clinical picture. When investigating unexplained chronic fatigue, NICE places vitamin D, B12 and folate (folic acid — AED 300) among additional tests ordered at the doctor's clinical discretion, not in mandatory screening for everyone.

Sometimes one more important test is needed

With prolonged unexplained tiredness, coeliac disease is worth keeping in mind. NICE explicitly recommends serological testing for coeliac disease in patients with prolonged unexplained fatigue, and also with unexplained iron, B12 or folate deficiency. The coeliac disease profile at GMS is AED 450.

Why "test everything" is a bad idea

Every laboratory marker has a reference range, and even in a completely healthy person some results can fall outside it by chance when many tests are done.

This is how a diagnostic cascade begins: repeat tests, further investigations, anxiety and sometimes treatment of changes that do not actually need treating.

So the doctor's job is not to order as many tests as possible but to choose the ones that can genuinely change what happens next. Tests without specific indications have a low diagnostic yield in tiredness.

When tiredness means seeing a doctor sooner

Do not settle for a routine check-up if tiredness comes with:

• unexplained weight loss;
• a prolonged fever;
• marked night sweats;
• enlarged lymph nodes;
• bleeding;
• increasing breathlessness;
• chest pain;
• marked muscle weakness or neurological symptoms.

A situation that deserves particular attention is when minimal physical or mental exertion makes you feel dramatically worse and recovery takes hours or days. This picture needs further assessment, including to rule out myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) and other conditions.

The key points

For constant tiredness there is no universal panel "for all vitamins and hormones".

For most patients it is better to start with a conversation with a doctor, an examination and a few tests: a full blood count, an assessment of iron stores, TSH, markers of carbohydrate metabolism and basic biochemistry. Other tests are added according to symptoms and risk factors.

This approach makes it possible to find the most likely and potentially correctable causes of tiredness — without unnecessary investigations.

Appointments at GMS

A GP consultation at GMS is AED 600. Tests can be done at the clinic, and the results and any need for further investigation discussed at the appointment. For routine health assessment there are check-up programmes.

Consultations are in Russian and English.

Sources

• NICE NG206. Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management
• NICE NG20. Coeliac disease: recognition, assessment and management
• NICE NG239. Vitamin B12 deficiency in over 16s: diagnosis and management

FAQ

Which blood tests should I have for constant tiredness?

Most often the doctor starts with a full blood count (AED 100), ferritin (AED 210), TSH (AED 125), fasting glucose (AED 45) or HbA1c (AED 130) and basic biochemistry — creatinine, electrolytes, liver function. For prolonged unexplained fatigue NICE also recommends coeliac screening (AED 450).

Should I check vitamin D and B12 if I am tired?

Not everyone needs to. B12 (AED 175) matters with a vegan or restrictive diet, stomach or bowel disease or surgery, certain autoimmune diseases and medications that impair absorption. Vitamin D (AED 250) is added with risk factors for deficiency. NICE treats these as additional tests at the doctor’s discretion, not screening for all.

When does tiredness need a doctor sooner?

If it comes with unexplained weight loss, prolonged fever, marked night sweats, enlarged lymph nodes, bleeding, increasing breathlessness, chest pain, marked muscle weakness or neurological symptoms. Also if minimal exertion makes you dramatically worse and recovery takes hours or days — this needs assessment, including for ME/CFS.

This article is for information only and does not replace a consultation. If you have symptoms, see a doctor.

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