Haemoglobin is a protein in red blood cells which carries oxygen around the body and gives the blood its red colour. This test measures the amount of haemoglobin in the blood and is a good measure of the blood's ability to carry oxygen around the body.
What might a low result mean?
Low levels of haemoglobin indicate that you may have anaemia, which can have many causes including pregnancy, blood loss, liver damage, and iron deficiency. A low haemoglobin level should be investigated in line with other symptoms and results.
What might a high result mean?
High levels of haemoglobin can indicate polycythaemia, where the body increases red blood cell production. This is done in order to compensate for chronically low oxygen levels which could be caused by lung disease, or by living at altitude. Other causes of high levels can include dehydration (this is a short term factor which resolves once you are fully hydrated) smoking, and bone marrow disorders.