What does haemoglobin mean?
Haemoglobin is the red, iron-containing protein inside vertebrate red blood cells that carries oxygen from the lungs to the rest of the body. It also participates in transporting some carbon dioxide back to the lungs and helps give blood its colour. In medicine, haemoglobin levels are commonly measured to assess anaemia, blood loss, and other conditions; low levels can cause fatigue, breathlessness, and weakness. The word is especially familiar from blood tests and medical reports, although it is also important in biology and physiology because haemoglobin is an exceptionally efficient oxygen-binding molecule. In British English the usual spelling is “haemoglobin,” while American English uses “hemoglobin.” The term is formal and technical rather than everyday, and is also used in discussions of genetic conditions, blood transfusion, and diseases that affect red blood cells.
nounAn iron-containing protein found in the red blood cells of vertebrates that transports oxygen from the lungs to tissues and helps carry carbon dioxide back to the lungs. It gives blood its characteristic red colour.
- The oxygen-carrying iron-containing protein in vertebrate red blood cells.
"The doctor checked her haemoglobin levels after the routine blood test."
"Haemoglobin carries oxygen from the lungs to the muscles during exercise."
"The test revealed a low haemoglobin count, suggesting anaemia."
The plural is uncommon in ordinary medical usage but may refer to different forms or variants of haemoglobin.
"Some genetic conditions affect the structure of haemoglobins."
Every breath you take depends on a tiny red protein that acts as the body’s oxygen-delivery system.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does haemoglobin come from?
The word combines Greek haima, meaning “blood,” with Latin globus, meaning “ball” or “globe.” The second element reflects the roughly globular form of the haemoglobin molecule. The compound entered English in the nineteenth century as the scientific name for the red respiratory pigment of blood.
Related word forms
How haemoglobin is actually used
The word is primarily used in medical and scientific contexts. British English generally uses “haemoglobin,” while American English generally uses “hemoglobin.”
Easily confused with haemoglobin
Haemoglobin is the standard British spelling, while hemoglobin is the standard American spelling of the same protein.
Haemoglobin is the oxygen-carrying protein in red blood cells, whereas haematin is an iron-containing pigment formed when haemoglobin is broken down.