A hemoglobin (Hgb) blood test measures the level of hemoglobin in your blood. Hemoglobin is an iron-rich protein in your red blood cells that carries oxygen from your lungs to the rest of your body. It is almost always measured as part of a complete blood count (CBC), a group of tests that look at the cells in your blood.
It is most often used to check for anemia, a condition in which the body does not make enough healthy red blood cells. A clinician may order it when a person has symptoms such as weakness, dizziness, or cold hands and feet; when there is a low-iron diet, a long-term infection, or significant blood loss from an injury or surgery; when there is a family history of an inherited blood disorder; or to help monitor treatment for anemia. A health care professional takes a blood sample from a vein in your arm using a small needle, and the draw usually takes less than five minutes.
Reference ranges are general and, per MedlinePlus, "may vary, based on the laboratory used and your age, race, and sex," so your own lab report is what applies to you — the numbers below are illustrative, not a personal cutoff or diagnosis. The MedlinePlus Medical Encyclopedia lists general adult ranges of about 13.8 to 17.2 g/dL for men and about 12.1 to 15.1 g/dL for women, with different ranges for newborns (about 14 to 24 g/dL) and infants (about 9.5 to 14 g/dL). MedlinePlus explicitly notes that "normal value ranges may vary slightly among different laboratories" because "some labs use different measurements or test different samples." Your result will be compared to the specific reference range printed on your own report.
A higher-than-usual hemoglobin level is general information, not a diagnosis, and the following are possible associations rather than a complete list. Per MedlinePlus, a high level can be seen with low blood oxygen present over a long period (chronic hypoxia), lung disease such as scarring or thickening of the lungs, heart disease including a congenital problem with the heart's structure or right-sided heart failure, living at a high altitude, cigarette smoking, dehydration, a bone marrow disease that raises red blood cell production, or a kidney tumor. A clinician interprets what it may mean in the context of your health.
A lower-than-usual hemoglobin level (by definition, anemia) is also general information, not a diagnosis, and these are possible associations rather than a complete list. Per MedlinePlus, a low level may be seen with bleeding or blood loss; a shortage of certain nutrients such as iron, folate, vitamin B12, or vitamin B6; the bone marrow not producing enough red blood cells (as can happen with leukemia, other cancers, drug toxicity, radiation, or infection); chronic illness; chronic kidney disease; the breakdown of red blood cells (hemolysis); or too much water in the body. A clinician interprets your result together with your history, symptoms, and other tests, and the reference range on your own lab report is what applies to you.
Reference ranges vary by laboratory, age, sex, and method — the range on your own report is what applies to you. A single value out of range doesn’t confirm any condition; your clinician interprets it alongside your symptoms, history, and other results. This page is general information, not medical advice.
General reference, not medical advice, and not a substitute for your clinician. Lab reference ranges and interpretation depend on the laboratory and on your individual situation — discuss your results with a licensed healthcare professional.