Hemoglobin
Also written as: Hgb, Hb
The oxygen-carrying protein inside red blood cells.
What it measures
The concentration of hemoglobin, the iron-containing protein in red blood cells that carries oxygen from the lungs to the rest of the body.
Why a doctor orders it
It is the value most often used to assess for anemia, and it is followed over time in people with chronic kidney disease, heavy menstrual bleeding, gastrointestinal bleeding, or during treatments that suppress blood counts.
What is generally associated with a higher result
Higher hemoglobin is broadly associated with dehydration, living at high altitude, smoking, chronic lung conditions, and less commonly with bone marrow disorders that overproduce red cells.
What is generally associated with a lower result
Lower hemoglobin defines anemia, which is a finding rather than a diagnosis. It is broadly associated with iron, vitamin B12, or folate deficiency, blood loss including slow gastrointestinal bleeding, chronic disease, kidney disease, and pregnancy.
Everyday things that move this number
Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:
- Hydration - being dehydrated concentrates the blood and raises the value
- Altitude of residence
- Pregnancy, which normally lowers it
- Time of day and posture during the draw, slightly
Questions to take to your appointment
- If this is low, do we know the cause?
- Should iron, B12, or folate be checked?
- Is there any reason to look for a source of bleeding?
Build a printable questionnaire with your own results →
Where to read more
MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .
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