Lab test glossary · Blood count
Hemoglobin: what it means
Also known as: Hgb, Hb
Hemoglobin is the oxygen-carrying protein in red blood cells; low levels define anemia, and high levels can point to dehydration or overproduction of red cells.
What it measures
Hemoglobin is the iron-containing protein that lets red blood cells carry oxygen from your lungs to the rest of your body. The hemoglobin concentration is a core part of a complete blood count (CBC) and the main number used to define anemia.
Typical range
Adult reference ranges are often around 13.5–17.5 g/dL for men and 12.0–15.5 g/dL for women, but this varies by lab, age, altitude, and pregnancy.
Reference ranges differ between labs and are printed on your own report — always read your result against that range, not a general one.
What a high result can mean
- Dehydration (concentrates the blood)
- Living at high altitude or smoking
- Lung or heart conditions that lower oxygen
- Polycythemia vera and other causes of red-cell overproduction
A high value is a starting point for a conversation, not a diagnosis — many causes are benign or temporary.
What a low result can mean
- Iron, B12, or folate deficiency
- Blood loss, including slow gastrointestinal bleeding
- Chronic disease, kidney disease, or bone-marrow conditions
Why the trend matters
Watching hemoglobin across years turns a borderline value into a clear picture: a slow decline can reveal ongoing blood loss long before any single result looks alarming.
When to talk to your doctor
A hemoglobin outside your lab's range — in either direction — is worth reviewing with your doctor, particularly with fatigue, shortness of breath, or dizziness.
Frequently asked questions
What is a normal hemoglobin level?
Adult ranges are often around 13.5–17.5 g/dL for men and 12.0–15.5 g/dL for women, but this varies by lab, age, altitude, and pregnancy — read your result against the range printed on your own report.
What does low hemoglobin mean?
Low hemoglobin defines anemia, which has many possible causes: iron, B12, or folate deficiency, blood loss, chronic disease, or bone-marrow conditions. The usual next step is to find the cause with related tests like ferritin and MCV.
Should I worry about high hemoglobin?
A mildly high hemoglobin is often from dehydration, smoking, or living at altitude. A persistent, unexplained elevation can reflect overproduction of red cells and is worth discussing with your doctor.
This page is general education about a common lab test — it isn’t medical advice and can’t interpret your specific result. What a value means depends on your history, symptoms, and the rest of your labs, which is a conversation for you and your clinician.