What is hemoglobin?
Hemoglobin (Hb or Hgb) is the iron-containing protein inside red blood cells that binds to oxygen in the lungs and delivers it throughout the body. It also carries carbon dioxide back to the lungs. The hemoglobin test is part of a Complete Blood Count (CBC) and is the primary test for diagnosing anaemia.
Hemoglobin normal range
| Group | Normal Range (g/dL) | Interpretation |
|---|---|---|
| Adult men | 13.5 – 17.5 | Normal |
| Adult women | 12.0 – 15.5 | Normal |
| Pregnant women | ≥ 11.0 | Acceptable in pregnancy |
| Children (6-12 yrs) | 11.5 – 15.5 | Normal |
| Severe anaemia | < 8.0 (any adult) | Urgent assessment |
LOW Hemoglobin — Anaemia
Low hemoglobin is called anaemia. The most common cause worldwide is iron deficiency due to poor diet, blood loss (heavy periods, GI bleeding) or poor absorption. Other causes: vitamin B12 or folate deficiency (megaloblastic anaemia), chronic kidney disease, chronic inflammatory conditions, thalassaemia and haemolytic anaemia. Symptoms include fatigue, weakness, pale skin, shortness of breath, dizziness and rapid heartbeat.
HIGH Hemoglobin — Polycythaemia
High hemoglobin (polycythaemia or erythrocytosis) causes include dehydration, high-altitude living, smoking, chronic lung disease (COPD) and polycythaemia vera (a bone marrow condition). Very high Hb thickens the blood and raises clot, stroke and heart attack risk.
Grades of anaemia
| Severity | Hb (g/dL) | Typical symptoms |
|---|---|---|
| Mild | 10 – 12 (women) / 10 – 13.5 (men) | Few or none |
| Moderate | 8 – 9.9 | Fatigue, breathlessness on exertion |
| Severe | < 8 | Breathlessness at rest, chest pain |
| Critical | < 6.5 | Emergency — may need transfusion |
Questions to ask your doctor
- What type of anaemia do I have?
- Do I need iron, B12 or folate supplements?
- Should I have ferritin and iron studies?
- Do I need a colonoscopy to check for GI bleeding?
- When should I retest?