Hemoglobin Blood Test

This test measures the concentration of hemoglobin in your whole blood. Hemoglobin is the oxygen-carrying protein in red blood cells, so the result reflects your blood's oxygen-carrying capacity. It does not show why a level is low or high; that usually needs the rest of the CBC (such as red cell size) and tests like ferritin or vitamin B12.

People who want to re-check a previous hemoglobin result, for example while treating iron-deficiency anemia; people whose clinician is monitoring hemoglobin during a treatment, such as testosterone therapy, where guidelines recommend checking hemoglobin and hematocrit before and during treatment; and people with heavy periods or a known blood condition who follow one value over time. If you have symptoms such as fatigue, weakness or dizziness and have not had blood work recently, start with the full CBC with differential instead.

Any time of day, with no fasting. When following treatment for anemia, a re-check is typically done a few weeks to months after starting, on your clinician's schedule. Dehydration can affect the result, so drink fluids normally beforehand.

Quest reports hemoglobin with reference ranges printed on your lab report, because normal values differ by age and sex. A low result may point to anemia, for example from iron deficiency, low vitamin B12, blood loss (including heavy menstrual periods), thalassemia, liver disease or other chronic conditions. A high result may be linked to lung or heart disease, sleep apnea, polycythemia vera, smoking or dehydration, and people who live at high altitude naturally run higher. Diet, activity and some medicines can also affect the level. An abnormal result does not always mean you have a condition that needs treatment; clinicians usually look at it alongside the rest of the CBC and tests such as ferritin. Review your result with a clinician. JustLabs results are informational and do not replace medical care.