Summary
What is haemoglobin?
Your blood is made up of red blood cells (RBCs), white blood cells (WBCs) and platelets. These float in fluid called plasma.
RBCs are the most common type of blood cell – they make up almost half of your blood - and they play an essential role in carrying oxygen to every cell in your body. All cells in every part of your body need oxygen to make energy so that they can function properly.
Haemoglobin is the red protein in RBCs that gives them their colour. Haemoglobin is made in the bone marrow, the spongy tissues inside many of your bones. To make haemoglobin, your body needs iron, and to make RBCs, your body needs vitamin B12 and folate.
Iron
Iron is crucial for making haemoglobin because it contains haem. Haem is the part of iron that binds to oxygen. Our bodies cannot make iron. It must be absorbed from our diet or from supplements. The amount of iron we absorb is decided by our body's needs. When we don’t have enough iron, our bone marrow cannot make haemoglobin because we do not have enough haem, which can lead to iron deficiency anaemia.
Vitamin B12 and folate
Vitamin B12 and folate are needed to make RBCs. (They are also needed to make and repair DNA and nerve cells.) If we don’t have enough vitamin B12 or folate, it can lead to a type of anaemia called megaloblastic anaemia, in which RBCs aren’t formed properly in our bone marrow, and they don't function properly, reducing their oxygen-carrying capacity.
Why get tested?
Measuring the amount of haemoglobin in your blood can help find out if you have enough RBCs to transport oxygen throughout your body. It helps screen for, diagnose, and monitor conditions that affect your blood or bone marrow. For more on this see red blood cell count.
Too few RBCs – anaemia
If the number of RBCs in your blood sample is10 per cent under what is considered normal, you are said to be anaemic.
Too many RBCs – polycythaemia (erythrocytosis)
If you have too many RBCs you are said to have polycythaemia. This makes your blood thicker than it should be, and without treatment it could increase your risk of blood clots.
There are two types of polycythaemia. Primary polycythaemia is due to a bone marrow problem (myeloproliferative neoplasm) as in polycythaemia vera (PV). PV is a condition in which the bone marrow produces too many RBCs, along with high numbers of WBCs and platelets. It is caused by a variant or mutation in particular genes, especially the JAK2 gene which is responsible for making a protein that is needed to produce blood cells.
Secondary polycythaemia is more common and occurs when a health condition is preventing oxygen from getting to your tissues. This may be due to problems with lung function, heart function or rarely, due to problems with the kidneys or adrenal glands (small glands on your kidneys). Your body makes up for lower oxygen levels by making more blood cells that can carry more oxygen.
Tests that are used together with haemoglobin
A measurement of haemoglobin is included in the full blood count (FBC), a routinely used test that assesses all the parts of your blood. It measures the number and the size of RBCs, white blood cells (WBCs), and platelets in your blood.
A haemoglobin test may also be ordered on its own if you are suspected of having a condition affecting your RBCs as well as to monitor any treatment you are having for a blood or bone disorder.
The test is also used before a surgical procedure to help make decisions about blood transfusion. It is also used to monitor a person’s condition if they have ongoing bleeding problems.
The results of other tests included in the FBC will be used to assess your RBCs.
Haemoglobin results are used in making calculations to gain more details about your red blood cells.
Possible further tests for anaemia
For more information see full blood count (FBC), and red blood cell (RBC) count.
Having the test
Sample
Blood.
Any preparation?
None.
Your results
Reading your test report
Your results will be presented along with those of your other tests on the same form. You will see separate columns or lines for each of these tests.
Low haemoglobin (anaemia) | High haemoglobin (polycythaemia) |
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Reference intervals - comparing your results to the healthy population
Your results will be compared to reference intervals (sometimes called a normal range).
If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation.
Reference intervals for haemoglobin vary between labs so you will need to go through your results with your doctor. Your doctor is the best person to interpret your results.
Example reference intervals for haemoglobin. | |
Adult male | 135 - 175 g/L |
Adult female | 115 - 165 g/L |
Reference intervals (normal ranges) for haemoglobin can vary between laboratories. This is because labs use different instruments and chemical processes to analyse samples. The reference intervals given here are used by many but not all laboratories. Haemoglobin reference intervals vary a lot between men and women. This may be important for transgender and gender-diverse people, especially when receiving gender affirming hormone therapy. They are also influenced by the age and ethnic origin of the person. g/L stands for grams per litre. |
More to know?
Questions to ask your doctor
The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.
You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.
Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:
More information
Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.
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