Biomarker · Blood count
Hemoglobin
Hemoglobin carries oxygen in red blood cells. What a hemoglobin test measures, what low or high values can point to, and how it fits into a complete blood count.
Written by LON6EVITY Editorial Team · Last updated
What hemoglobin does
Hemoglobin is the iron-containing protein in red blood cells that carries oxygen from the lungs to the rest of the body and brings carbon dioxide back.
Low and high values
According to MedlinePlus, low hemoglobin can be a sign of anaemia, which may be caused by iron deficiency, vitamin deficiencies, blood loss, or chronic disease. High hemoglobin can occur with lung or heart disease, living at high altitude, smoking or dehydration.
How it is tested
Hemoglobin is usually measured as part of a complete blood count (CBC). If it is low, further tests such as ferritin, vitamin B12 and folate help find the cause.
Reference ranges
Reference ranges differ between laboratories, units and methods, and depend on age, sex and your overall clinical picture. A single result is not a diagnosis — interpret it with a qualified clinician.
Factors that can affect the result
- Iron status
- Vitamin B12 and folate
- Blood loss
- Altitude
- Smoking
- Hydration
Questions people commonly ask
- Does low hemoglobin always mean iron deficiency?
- No. Iron deficiency is a common cause, but there are others, which is why follow-up tests are used.
Related biomarkers
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Understand your biomarkers in context
What does this mean for your own health data? Log your results, follow trends over time and bring an organised summary to your next doctor's appointment.
Sources
- Hemoglobin Test. MedlinePlus, U.S. National Library of Medicine.
- Complete Blood Count (CBC). MedlinePlus, U.S. National Library of Medicine.