Hemoglobin (Hgb) blood test: what it means
What it measures
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.
Why it’s ordered
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.
General reference range
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.
If it’s high
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.
If it’s low
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.
A result is not a diagnosis
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.
Medicines that can move this result
Androgens stimulate red cell production, so hemoglobin and hematocrit climb. The label lists polycythemia among hematologic reactions and venous thromboembolism among vascular ones, and tells prescribers to recheck these levels periodically during long-term therapy rather than only at the start.
Source ↗This is a lab-made copy of erythropoietin, the kidney hormone that signals red cell production, so raising hemoglobin is the purpose of the drug. The dose is deliberately kept to the lowest that avoids transfusion, because the boxed warning ties higher hemoglobin targets to increased risk of death, myocardial infarction, stroke and thrombosis.
Source ↗Hydroxyurea suppresses the bone marrow as part of how it works. Per the label, low white cells are usually the first and most common sign; anemia happens less often and seldom appears without a preceding drop in white cells — which is why the full blood count, not hemoglobin alone, is monitored on this drug.
Source ↗By blocking folate, methotrexate slows the marrow's production of all blood cell lines, hemoglobin included — the reason regular blood counts are part of taking it for arthritis, psoriasis or cancer.
Source ↗Zidovudine suppresses the marrow precursors that become red blood cells. The label states a reduction in hemoglobin may occur as early as 2 to 4 weeks, with toxicity tied to pre-treatment marrow reserve, dose and duration of therapy — serious enough that it appears in the boxed warning.
Source ↗This antibiotic can suppress the bone marrow, and the risk grows with time on the drug. The label directs weekly complete blood counts for anyone receiving linezolid, particularly beyond two weeks; where the outcome was known, counts rose back toward pre-treatment levels once the antibiotic was stopped.
Source ↗The label does not pin this on a single cause: it attributes anemia on NSAIDs to fluid retention, to occult or gross gastrointestinal blood loss, or to an incompletely described effect on red cell production. The effect scales with dose — in two post-marketing studies a hemoglobin drop of 1 gram or more was seen in 17.1% of patients taking 1,600 mg of ibuprofen daily and 22.8% of those taking 2,400 mg daily.
Source ↗Dapsone shortens how long red cells survive in the bloodstream. The label calls this dose-related hemolysis its most common adverse effect and notes it occurs in people with and without G6PD deficiency; most patients lose 1 to 2 g of hemoglobin, and those who are G6PD deficient have greater responses.
Source ↗Do not stop a prescribed medicine over a lab number. These are recognised associations, not a finding about your result — your value may have nothing to do with any medicine you take, and the list is not complete. Bring it to whoever prescribed the drug; they can weigh it against why you are taking it.
Frequently asked
- What does the Hemoglobin (Hgb) blood test measure?
- 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.
- What is a normal Hemoglobin (Hgb) blood test range?
- 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.
- What does a high result mean?
- 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.
- What does a low result mean?
- 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.
Other lab tests
Sources
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.