What is Haemoglobin (Hb)?
your blood count
Haemoglobin is the oxygen-carrying protein inside red blood cells. It is the standard screen for anaemia and is affected by iron, B12, folate, bleeding, and chronic disease.
Haemoglobin binds oxygen in the lungs and carries it to the tissues. A low value means the blood carries less oxygen, producing symptoms like fatigue, breathlessness, dizziness, and pallor. The result is read alongside MCV, ferritin, and the rest of the blood count to identify the cause of any abnormality.
Test facts
- Unit
- g/L
- Sample
- Whole blood
- Fasting
- No fasting needed
- Turnaround
- 1 day
What does low Haemoglobin (Hb) mean?
Low Hb means anaemia. The most common causes are iron deficiency, B12 or folate deficiency, blood loss (including heavy periods), chronic inflammation, and kidney disease. The fatigue is often gradual and easy to miss without a test.
What does high Haemoglobin (Hb) mean?
High Hb is uncommon. It can reflect dehydration, time at altitude, smoking, or more rarely the rare blood disorder polycythaemia. A one-off elevation is rarely alarming but deserves a follow-up.
Panels that measure Haemoglobin (Hb)
- Essentials
- Deep Baseline
- Female Annual
- Male Annual
- Pre-Conception
- Iron Quick
- Iron & Anaemia
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This is general information about the marker, not an assessment of your values and not medical advice. Last updated: May 2026.