Introduction
Do you wake up feeling tired even after a full night's sleep? Do you struggle to concentrate at work, feel unusually exhausted throughout the day, or experience persistent low mood without knowing why?
While stress, anxiety, and emotional exhaustion can affect your energy levels, constant fatigue and low mood may sometimes be linked to underlying physical health conditions. Iron deficiency, vitamin deficiencies, thyroid disorders, and blood sugar abnormalities can contribute to tiredness, weakness, difficulty concentrating, and changes in mood.
This World Mental Health Day, it is important to remember that mental and physical health are closely connected. Before assuming that stress is the only reason you feel exhausted, consider discussing your symptoms with a healthcare professional.
Certain blood tests can help identify medical conditions that may contribute to fatigue and low energy. In this blog, we explore five blood tests that doctors may recommend to investigate persistent tiredness and understand when further evaluation may be necessary.
Why Am I Always Tired Even After Sleeping?
Feeling tired occasionally is normal, particularly after a demanding day, insufficient sleep, or an emotionally stressful experience. However, persistent fatigue that interferes with your daily routine deserves attention.
Common causes of tiredness and low energy include:
- Poor sleep quality or an irregular sleep schedule.
- Chronic stress, anxiety, or depression.
- Iron deficiency or anaemia.
- Vitamin B12 deficiency.
- Thyroid disorders.
- Diabetes or abnormal blood glucose levels.
- Inadequate nutrition or dehydration.
- Certain medications and other underlying medical conditions.
Fatigue can have several causes at the same time. For example, a person may experience work-related stress while also having iron deficiency or a thyroid problem.
Blood tests can help investigate some physical causes, but they cannot diagnose every cause of tiredness or replace an assessment of mental health.
5 Blood Tests to Check for Persistent Tiredness and Low Mood
1. Complete Blood Count (CBC): Check for Anaemia
A Complete Blood Count (CBC) is a commonly used blood test that measures different components of your blood, including red blood cells, white blood cells, haemoglobin, and platelets.
Red blood cells contain haemoglobin, which carries oxygen throughout the body. When haemoglobin levels are low, your tissues may receive less oxygen than they need.
Anaemia can contribute to symptoms such as:
- Persistent tiredness and weakness.
- Dizziness or light-headedness.
- Pale skin.
- Shortness of breath during physical activity.
- Difficulty concentrating.
- Reduced exercise tolerance.
Iron deficiency is a common cause of anaemia, although anaemia can also result from vitamin deficiencies, chronic disease, blood loss, and other conditions.
Why this test matters: A CBC can help identify anaemia and other blood abnormalities that may require further investigation.
2. Ferritin and Iron Studies: Investigate Iron Deficiency
Iron helps your body produce haemoglobin. When iron stores become depleted, you may experience fatigue and reduced physical stamina, sometimes even before anaemia develops.
A serum ferritin test measures a protein that reflects the body's iron stores. Depending on your symptoms and medical history, your doctor may also recommend additional iron studies.
Signs that may occur with iron deficiency include:
- Feeling exhausted even after adequate rest.
- Weakness and reduced stamina.
- Difficulty concentrating.
- Headaches or dizziness.
- Restless legs in some individuals.
- Increased hair shedding in certain cases.
Iron deficiency can occur because of inadequate dietary intake, heavy menstrual bleeding, pregnancy, blood loss, or problems with iron absorption.
Why this test matters: A CBC alone may not identify iron deficiency when haemoglobin is still within the normal range. Ferritin and other appropriate iron studies can provide additional information.
Do not start iron supplements without medical advice. Unnecessary iron supplementation can be harmful, and the underlying cause of a deficiency should be investigated.
3. Thyroid Function Test (TSH): Check Your Thyroid Health
Your thyroid gland produces hormones that influence metabolism, energy use, and several important body functions.
An underactive thyroid, known as hypothyroidism, can cause persistent fatigue and may also affect mood and concentration.
Common symptoms of hypothyroidism include:
- Constant tiredness or sluggishness.
- Feeling unusually sensitive to cold.
- Unexplained weight gain.
- Constipation.
- Dry skin or hair changes.
- Difficulty concentrating.
- Low mood.
A thyroid-stimulating hormone (TSH) test is commonly used to evaluate thyroid function. Depending on the result and clinical situation, your doctor may recommend a free T4 test or additional investigations.
Thyroid symptoms can overlap with those of stress, sleep disorders, depression, and other medical conditions. Symptoms alone cannot confirm a thyroid problem.
Why this test matters: Identifying and treating an underactive thyroid may improve fatigue and other related symptoms when thyroid dysfunction is the cause.
4. Vitamin B12 Test: Investigate Low Energy and Brain Fog
Vitamin B12 is essential for red blood cell formation and normal nervous system function.
Low vitamin B12 levels can cause fatigue, weakness, anaemia, and neurological symptoms. Some people also experience difficulty concentrating, memory problems, or changes in mood.
Symptoms that may be associated with vitamin B12 deficiency include:
- Persistent tiredness.
- Tingling or numbness in the hands and feet.
- Difficulty with balance.
- A sore or unusually smooth tongue.
- Memory or concentration difficulties.
- Certain types of anaemia.
People following restrictive diets, those with certain digestive conditions, and people taking some medications may have an increased risk of vitamin B12 deficiency.
Importantly, vitamin B12 deficiency can sometimes cause neurological problems even when a person does not have obvious anaemia.
Why this test matters: A vitamin B12 blood test can help identify a deficiency that may require treatment. Borderline results may need further assessment depending on the symptoms and clinical circumstances.
5. Blood Glucose or HbA1c Test: Check for Blood Sugar Problems
Changes in blood glucose levels can contribute to fatigue and other symptoms. Diabetes may sometimes remain undetected because early symptoms can be mild or absent.
Two commonly used tests are fasting blood glucose and HbA1c.
Fasting blood glucose (FBS) measures blood sugar after a period of fasting, usually at least eight hours.
HbA1c estimates average blood glucose levels over approximately the previous two to three months and generally does not require fasting.
Symptoms that can occur with diabetes include:
- Increased thirst.
- Frequent urination.
- Unusual tiredness.
- Blurred vision.
- Unexplained weight changes.
- Slow-healing wounds.
These symptoms are not specific to diabetes, and fatigue alone does not mean that you have high blood sugar.
Why these tests matter: Fasting glucose and HbA1c can help identify diabetes or prediabetes when used according to established diagnostic criteria.
