Hemoglobin
The iron-containing protein in red blood cells that carries oxygen.
| Typical reference range (male) | 13.2–17.1 g/dL |
| Typical reference range (female) | 11.7–15.5 g/dL |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
Hemoglobin binds oxygen in the lungs and releases it in tissues. Each red cell contains about 270 million hemoglobin molecules, and making it requires iron, B12, folate and other nutrients.
Why it matters
Hemoglobin is the primary measure used to define anemia. Low levels reduce oxygen delivery, causing fatigue and breathlessness; high levels increase blood viscosity.
What a high result can mean
High hemoglobin can result from dehydration, smoking, altitude, sleep apnea, lung or heart disease, testosterone or EPO use, and polycythemia vera.
What a low result can mean
Low hemoglobin indicates anemia, from iron deficiency (very common in menstruating women), blood loss, B12 or folate deficiency, chronic inflammation, kidney disease, hemolysis, thalassemia or marrow disorders. Endurance athletes may have slightly low values due to plasma expansion.
What affects the result
Hydration, altitude, smoking, pregnancy and testosterone therapy all shift values. Interpret with MCV, RDW, ferritin and reticulocytes to identify the cause of abnormal results.
Units and conversion
Usually reported in g/dL.
- From g/L: multiply by 0.1 to get g/dL
- From mmol/L: multiply by 1.611 to get g/dL
Also called on lab reports
Hgb, Hb, Haemoglobin, HGB, Blood
Related tests: Red Blood Cells
This page is educational and does not replace advice from a healthcare professional.