Hemoglobin

Hemoglobin is the protein inside red blood cells that carries oxygen from your lungs to the rest of your body.

It is measured as part of a complete blood count (CBC) and reflects how well your blood can deliver oxygen to your tissues.

Hemoglobin is the main marker used to detect anemia (low hemoglobin) and to flag unusually high red blood cell levels.

If hemoglobin is too low, your body may have difficulty getting enough oxygen from the blood, particularly when you are exerting yourself. If hemoglobin is too high, it may reflect increased red blood cell production (sometimes as a response to chronically low oxygen levels) or low blood volume.

Hemoglobin levels naturally differ by sex and can also be influenced by factors such as pregnancy, altitude, smoking, hydration status, and overall health.

- Below range: Lower hemoglobin levels may indicate anemia. Anemia can have many causes, including iron deficiency, vitamin deficiencies, chronic disease, blood loss, or bone marrow conditions. Further testing is usually needed to determine the reason.

- In range: Hemoglobin levels are within expected limits for your sex. If you have symptoms, interpretation may still depend on other blood markers and clinical context.

- Above range: Higher hemoglobin levels may reflect dehydration, living at high altitude, smoking, or increased red blood cell production. Persistently elevated levels may require evaluation to rule out underlying conditions.