Fatigue Test: Causes, Diagnosis, and Lab Investigations Explained

If you are feeling tired after a long day, this is normal. However, if you are feeling tired despite having had plenty of sleep, then this could indicate an underlying health issue. Fatigue can affect our physical energy, mental concentration, productivity, and everyday activities. Although fatigue can be caused by poor-quality sleep, stress, and poor diets, there are some medical conditions that can be the cause. Fatigue tests are usually performed with a series of blood tests and other medical investigations to help find any possible causes. It is important to know the cause of fatigue to ensure the appropriate treatment can be provided.

What Is Fatigue?

Fatigue is a prolonged feeling of tiredness or not getting enough sleep. It can present in many ways, causing the person to feel lethargic, lacking motivation, unable to concentrate, and having difficulty completing everyday tasks. Fatigue can be both short-term and long-term. Fatigue can be short-term if caused by physical activity, lack of sleep, or emotional stress. However, if it is prolonged or worsening over weeks, then it should not be ignored and should be reported to a doctor.

Common Causes of Fatigue

There are many different causes of fatigue. Identifying the cause can help the doctor know what investigations to perform.

1. Iron Deficiency and Anaemia

Iron is an important mineral used to produce a protein called haemoglobin within red blood cells. This helps carry oxygen throughout the body. Lack of iron can affect the production of haemoglobin causing an iron deficiency anaemia. Symptoms can include feeling tired, lightheadedness, breathlessness, and fatigue.

2. Thyroid Disorders

The thyroid gland produces hormones to control the amount of energy used in the body and the metabolic rate. Hypothyroidism can cause fatigue, weight changes, constipation, and sensitivity to cold.

3. Vitamin Deficiencies

People who feel tired and weak can also suffer from low vitamin levels such as B12 and D. This can affect red blood cells and nerves.

4. Diabetes and Blood Sugar Imbalance

Fatigue can be a symptom of diabetes. The body may not be able to utilise glucose, causing symptoms such as dehydration, frequent urination, and excessive thirst due to high blood glucose levels.

5. Sleep Problems and Stress

Lack of sleep can cause fatigue. Energy levels can be affected by sleep apnoea and emotional stress. Even if you are getting plenty of sleep in bed, you can still feel tired throughout the day.

6. Other Medical Conditions

Fatigue can also be caused by chronic infections, kidney disease, liver disease, heart disease, and inflammatory conditions. Some medications can also cause fatigue as a side effect.

Which Blood Tests Are Recommended for Fatigue?

There is no single blood test for fatigue. Doctors decide which tests to perform based on your symptoms, medical history, age, lifestyle, and physical examination.

1. Complete Blood Count (CBC)

The Complete Blood Count looks at different aspects of your blood, including red blood cells, white blood cells, haemoglobin, and platelets. This can help diagnose anaemia and some infections and blood disorders causing fatigue.

2. Iron Profile

This includes serum iron, ferritin, total iron-binding capacity, and transferrin saturation. This shows your iron levels within your body and can detect iron deficiencies.

3. Thyroid Function Test (TFT)

Thyroid Function Tests usually include Thyroid Stimulating Hormone (TSH), sometimes Free T3 and Free T4. This helps to assess thyroid function and can detect hypothyroidism, hyperthyroidism, and other thyroid disorders.

4. Vitamin B12 Test

This shows what your levels of vitamin B12 are. Deficiencies can cause fatigue, weakness, anaemia, and nerve problems.

5. Vitamin D Test

The 25-hydroxy vitamin D test is usually used to show your vitamin D levels. Deficiency can affect mineral levels involved in bone and muscle development and can be linked to weakness.

6. Blood Glucose and HbA1c

A blood glucose test is a lab test to see what your glucose (sugar) levels are in your blood at that point in time. The HbA1c test is a blood test that gives an average blood glucose reading over the last 2-3 months. This can help assess diabetes and blood sugar levels.

7. Kidney Function Test (KFT)

Kidney Function Tests show various markers (Creatinine, Urea and Electrolytes). Kidney disease can cause imbalances in minerals and fluids in the body and can cause weakness and fatigue.

8. Liver Function Test (LFT)

Liver Function Tests include various blood tests looking at enzymes, proteins, and other substances involved in liver health. This may be helpful to help diagnose fatigue if symptoms and medical history indicate a liver disorder.

How Is Fatigue Diagnosed?

If you are experiencing fatigue, you need to visit a doctor. They may ask you about your symptoms, how long you have been feeling tired, if it is affecting your normal activities, and if you have any other symptoms such as trouble sleeping, lightheadedness, and fever. After a physical examination, specific blood tests may be performed. Blood tests should not be viewed on their own and should be considered along with symptoms and medical history. If initial investigations do not give a reason for fatigue, further tests or specialist investigations may be recommended.

Conclusion

Correctly interpreting symptoms of prolonged fatigue may require specific lab tests. Molecular Diagnostics and Therapy is a NABL and NABH certified diagnostic centre offering comprehensive laboratory and imaging services to diagnose various health conditions. Doctors may recommend that you have some blood tests to help determine the cause of your fatigue. These may include a Complete Blood Count, Thyroid Function Test, Iron tests, Vitamin B12, Vitamin D, Blood Sugar, and Kidney/Liver Function Tests depending on your symptoms and medical history. Diagnostic reports can help doctors identify the underlying cause and decide if further tests and/or treatment are required.