Skip to main content
Your session has expired. Reloading...

Doctor's Assessment Included

Every result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.

Hematology

Haemoglobin levels: what do they tell you about your blood?

Hemoglobin is your primary oxygen-delivery molecule and a cornerstone metric for endurance performance. Monitoring hemoglobin levels helps athletes assess training adaptations, identify early signs of overtraining, and optimise recovery strategies.

Reference Ranges

Male
mmol/l
Low 8.5 Normal 11 High
Female
mmol/l
Low 7.5 Normal 10 High

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

What It Measures

This test measures the concentration of haemoglobin in your blood, expressed in millimoles per litre (mmol/L). Normal values are 8.5–11.0 mmol/L for men and 7.5–10.0 mmol/L for women. The difference is because testosterone stimulates red blood cell production.

Haemoglobin is almost always measured as part of a complete blood count, alongside haematocrit (the percentage of red blood cells in your blood), MCV (the size of red blood cells), and erythrocyte count. Together, these values provide a complete picture of your oxygen transport and the potential cause of anaemia.

Why It Matters

Anaemia affects an estimated 8% of the Dutch population and is approximately twice as common in women as in men. It is often underdiagnosed because the symptoms — fatigue, concentration problems, shortness of breath — are non-specific and develop gradually.

The most common cause is iron deficiency anaemia, especially in women with heavy menstrual bleeding. But anaemia can also indicate a vitamin B12 or folate deficiency, chronic diseases (kidney conditions, autoimmune diseases), gastrointestinal blood loss, or more rarely bone marrow disorders.

Too high haemoglobin (polycythaemia) occurs less frequently but is also relevant. It can occur with chronic lung diseases, smoking, dehydration, or the bone marrow disorder polycythaemia vera. High haemoglobin makes the blood thicker and increases the risk of thrombosis.

When to Test

A haemoglobin test is useful for symptoms consistent with anaemia: chronic fatigue, pallor, dizziness, palpitations during exercise, shortness of breath, or concentration problems. For women with heavy menstrual bleeding, periodic monitoring is recommended.

With a known chronic disease (kidney problems, rheumatoid arthritis, inflammatory bowel disease), haemoglobin is regularly measured as these conditions can cause anaemia. During pregnancy, Hb monitoring is standard.

Fasting is not required for a haemoglobin test.

Symptoms

Low Levels

Low haemoglobin (anaemia) causes oxygen deficiency in your tissues. The most common symptoms are fatigue that does not improve with rest, pallor (especially visible in the face and inner eyelids), dizziness, shortness of breath with mild exertion, palpitations, headaches, and concentration problems. In severe anaemia (Hb below 5 mmol/L), it can lead to heart failure.

High Levels

High haemoglobin (polycythaemia) makes the blood thicker. Symptoms may include headaches, dizziness, blurred vision, flushed complexion, itching (especially after a warm bath), and a heavy feeling in the legs. With significantly elevated values, the risk of blood clots increases (thrombosis, pulmonary embolism, stroke). Common causes are smoking, chronic lung diseases, dehydration, and more rarely the bone marrow disorder polycythaemia vera.

Lifestyle Tips

For anaemia due to iron deficiency, an iron-rich diet helps: red meat, liver, legumes, dark green vegetables, and whole grain products. Combine plant-based iron with vitamin C and avoid tea and coffee with meals. For vitamin B12 deficiency, animal products or supplementation are needed.

For high haemoglobin, stopping smoking is the most important measure if it is the cause. Adequate hydration prevents dehydration from artificially raising haemoglobin. For polycythaemia vera, phlebotomy is the standard treatment.

Frequently Asked Questions

What is a normal haemoglobin level?
For men, normal is 8.5–11.0 mmol/L; for women, 7.5–10.0 mmol/L. During pregnancy, mildly decreased haemoglobin (down to 6.8 mmol/L) is physiologically normal due to increased blood volume.
What is the difference between haemoglobin and ferritin?
Haemoglobin measures the oxygen-carrying capacity of your blood right now. Ferritin measures your iron stores. Ferritin drops before haemoglobin in iron deficiency — it is the earlier warning. Together they provide a more complete picture.
Do I need to fast before a haemoglobin test?
No, fasting is not required. Haemoglobin is a standard component of the blood count and is not affected by food intake.
How quickly does haemoglobin improve with iron supplementation?
With adequate iron supplementation, haemoglobin typically rises noticeably within two to four weeks. Full recovery can take six to twelve weeks. It is important to continue supplementation for three to six months to also replenish iron stores (ferritin).
Can exercise affect my haemoglobin?
Yes, endurance athletes can have lower haemoglobin due to so-called sports anaemia — blood plasma volume increases, diluting the haemoglobin. This is not true anaemia. Conversely, training at altitude can raise haemoglobin.
What is Hb in mmol/L versus g/dL?
In the Netherlands, haemoglobin is expressed in mmol/L. Internationally, g/dL is often used. The conversion is: 1 mmol/L = 1.61 g/dL. An Hb of 8.5 mmol/L corresponds to approximately 13.7 g/dL.