You sleep enough, eat fairly well, and yet you feel exhausted all day. Fatigue is one of the most common complaints, but also one of the hardest to pin down. A blood test can bring clarity. Here are seven blood values directly linked to fatigue.
1. Ferritin: your iron stores
Ferritin is the storage form of iron. It drops before haemoglobin does, making it the earliest marker of iron deficiency. Symptoms can appear at levels below 30 ug/L, even though the official lower limit is often set at 15 ug/L. Women with heavy periods, vegetarians and athletes are most at risk.
Common signs: persistent tiredness, concentration problems, hair loss, cold extremities, restless legs.
2. TSH: thyroid function
Your thyroid regulates metabolism, energy and body temperature. TSH (thyroid-stimulating hormone) is the key marker. Elevated TSH indicates an underactive thyroid (hypothyroidism), which slows your metabolism and causes fatigue, weight gain and feeling cold.
Thyroid conditions are more common in women and after age 40. They are frequently missed because symptoms develop gradually.
3. Vitamin D: the sunshine vitamin
Between October and March, your skin produces virtually no vitamin D in northern countries like the Netherlands. An estimated 40-60% of the Dutch population has suboptimal levels. Deficiency contributes to fatigue, muscle weakness and low mood.
4. Vitamin B12: essential for nerves
Vitamin B12 is crucial for red blood cell production and nerve function. Deficiency develops slowly and causes fatigue, tingling in hands and feet, memory issues and mood changes. Vegetarians, vegans, older adults and proton-pump inhibitor users are most at risk.
5. Haemoglobin: oxygen transport
Haemoglobin carries oxygen from your lungs to your tissues. Low haemoglobin (anaemia) means your muscles and organs receive less oxygen, causing tiredness, weakness and breathlessness during exertion. Always investigate the underlying cause.
6. CRP: inflammation signal
CRP (C-reactive protein) rises when inflammation is present. Chronic low-grade inflammation is an underestimated cause of fatigue. Your immune system is constantly active, draining energy. Causes include infections, autoimmune conditions, gut inflammation and excess weight.
7. HbA1c: blood sugar average
HbA1c reflects your average blood sugar over 2-3 months. Both elevated and fluctuating blood sugar can cause fatigue. In prediabetes, insulin works less effectively, so glucose does not enter your cells properly. Signs include energy dips after meals, excessive thirst and difficulty losing weight.
What can you do?
If you have been tired for weeks without a clear explanation, a blood test is a logical first step. A fatigue panel covers all seven values above. Take borderline results seriously, discuss abnormalities with your doctor, and combine testing with good sleep hygiene, exercise and nutrition.
Frequently asked questions
When should I see a doctor about fatigue?
If fatigue persists for more than two weeks without an obvious cause, especially with additional symptoms like unexplained weight loss or night sweats.
Does insurance cover blood tests?
Blood tests requested by your GP are usually covered under basic Dutch health insurance (after your deductible). Self-ordered tests are paid out of pocket.
How quickly do I get results?
Typically within 2-5 working days. Some values are available within 24 hours.
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