Alternative Names serum haemoglobin, total haemoglobin
Definition Haemoglobin is a protein in red blood cells. It carries oxygen from the lungs to cells throughout the body, and carries carbon dioxide from the cells to the lungs. A haemoglobin test measures the level of this protein in a sample of blood.
Who is a candidate for the test? Often, this test is done as part of a full blood count, or FBC. Or it may be done:
during pregnancy
during infancy
when a person has symptoms of anaemia, such as lack of energy, pale skin, and shortness of breath
when a person is being treated for anaemia
when family history or ethnic or racial background puts a person at risk for a blood disorder. Examples include haemoglobin disorders, sickle cell disease, and thalassaemia.
How is the test performed? Blood for the test is usually taken from a person's forearm. First, a tight band is put on the upper arm to make the veins swell below it. An area of skin on the forearm over the vein chosen is cleansed. Then a needle is inserted into the vein and a sample of blood is collected in a tube.
Occasionally blood is taken from another site, such as a finger or heel. If so, the skin is cleansed and pricked with a sharp tool called a lancet. Drops of blood are collected in a tiny tube. The blood is analysed at a laboratory.
What is involved in preparation for the test? Generally, no preparation is needed.
What do the test results mean? Age, sex, and other factors cause normal ranges for haemoglobin to vary. Generally, healthy test ranges are:
newborns - 140 to 225 grams of haemoglobin per litre of blood (g/l)
children 6 months to 6 years -- 95-140 g/l
children 6 to 18 years - 100 to 155 g/l
men 18 or older - 140 to 180 g/l
women 18 or older -120 to 160 g/l
pregnant women -- at least 110 g/l
Low values of haemoglobin generally mean that a person has a low red blood cell count, which is also called anaemia. Anaemia has many possible causes. Common causes include:
excessive menstrual bleeding in women
gastrointestinal bleeding, such as that from bleeding peptic ulcers and bowel cancer
malnutrition
increased nutritional needs, which occurs during rapid growth periods of childhood and in pregnancy
inherited causes, such as sickle cell disease, a condition that causes abnormally shaped red blood cells
Increased haemoglobin levels can occur for several reasons. Common causes include:
dehydration, which causes a temporary increase in haemoglobin that goes away once someone becomes re-hydrated
chronic obstructive pulmonary diseases, such as emphysema, which is usually due to smoking cigarettes
blood cancer, such as a cancer called polycythaemia vera
Depending on the results of this test and the suspected cause of the results, the doctor may suggest a treatment or further tests.
Author: Francesca Coltrera, BA Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 21/09/2004 Contributors Potential conflict of interest information for reviewers available on request
