The haemoglobin test can be performed to screen, diagnose or assess a number of different conditions that can affect red blood cells and the haemoglobin the blood. Haemoglobin blood tests can be done with a hemocrit to give a quick test for the number of red blood cells or as part of a CBC or complete blood count test. It is also used in cases where anaemia is suspected (and will be diagnosed by low red blood cell count, haemoglobin and hemocrit) or needs to be evaluated or to test or monitor polycythaemia (characterized by high red blood cell count, hemocrit and haemoglobin). It can also be used to evaluate a patient’s response to treatment for both conditions or to help decide if a blood transfusion is necessary.

Sometimes an irregular number of mature red blood cells are released (too many or too few) into the bloodstream because of conditions that affect red blood cell creation in a person’s bone marrow. Sometimes a person may be affected by the lifespan of circulating red blood cells. If haemolysis occurs (an increase in red blood cell production) or the person loses a significant amount of blood, and their bone marrow cannot replace the new red blood cells quickly enough the person’s red blood cells and haemoglobin levels will decrease, causing anaemia.

The haemoglobin test will evaluate if there is a problem with the lifespan or production of red blood cells but will not be able to determine what the underlying cause is.

If your doctor has ordered a complete blood count you may also require other tests like a reticulocyte count, a blood smear, a vitamin B12 test, iron studies or folate levels. For more severe cases your doctor may also request a bone marrow exam.

Even patients such as you yourself can order such tests, under the protection of complete privacy. A haemoglobin test can be ordered on its own, with hemocrit or as part of a complete blood count when doing a medical exam. Symptoms of anaemia that may warrant a haemoglobin test include low energy levels, fainting, weakness, pale colour or shortness of breath. Symptoms of polycythaemia that may present and require a haemoglobin test for evaluation include dizziness, disturbed vision, headaches and an enlarged spleen.

Very low levels of red blood cells may indicate the presence of haemolytic anaemia, thalassemia, chronic or acute bleeding, nutritional deficiencies, kidney failure or severe or chronic kidney disease and bone marrow disorders. Excessively high haemoglobin levels could be an indication of pulmonary disease, congenital heart disease, kidney tumours or dehydration.

Haemoglobin blood tests test may be taken more than once or regularly by someone who has chronic bleeding, polycythaemia or anaemia, to check how they are responding to their treatment.