Haemoglobin

What is being analysed?
This test measures the concentration of haemoglobin, a protein found inside red blood cells, and is a good indicator of the blood’s ability to carry oxygen throughout the body. Haemoglobin carries oxygen from the lungs to the cells. If the haemoglobin level is low, you may have anaemia, a condition in which the body does not get enough oxygen, causing tiredness and weakness.
Haemoglobin rises as the number of red blood cells increases. Haemoglobin falls below normal, indicating anaemia, when the body produces fewer red blood cells or destroys more of them, or when blood is lost through bleeding.

How is the sample collected for testing?
The test is carried out on a blood sample taken with a needle from a vein in the arm, by finger-prick (children and adults) or by heel-prick (newborn babies).

How is it used?
When is it requested?
What does the test result mean?
Is there anything else I should know?

How is it used?
The haematocrit is an integral part of a proper assessment of health. The test is used to:

• measure the severity of anaemia (too few red blood cells) or polycythaemia (too many red blood cells), assess the severity of these conditions and monitor their response to treatment.
• monitor the response to treatment of anaemia or polycythaemia.
• help decide whether a transfusion is needed if anaemia is severe.

When is it requested?
The haemoglobin test is usually requested as part of the full blood count (FBC), which is requested for many different reasons, including a general health screen. The test is also repeated in patients with bleeding problems, chronic anaemia or polycythaemia.

What does the test result mean?
Normal values in adults are 12 to 18 g/dL. Values above the normal limit can be the result of:

• dehydration
• excessive production of red blood cells by the bone marrow
• severe, prolonged illness
• numerous other conditions

Values below normal occur with anaemia, which can be the result of:

• deficiency of iron or essential vitamins such as B12, folate or B6
• inherited haemoglobin defects affecting red blood cells
• other inherited red blood cell defects
• liver cirrhosis
• excessive bleeding
• excessive destruction of red blood cells
• diseases of the spleen
• other chronic diseases
• bone marrow failure or aplastic anaemia
• bone marrow cancer.

Is there anything else I should know?
Haemoglobin normally falls during pregnancy.

Haemoglobin peaks at around 8 am and is lowest at around 8 pm. Heavy smokers have higher levels than non-smokers.

Living at high altitude increases haemoglobin by increasing the number of red blood cells. The body produces more red blood cells in response to the lower oxygen levels at altitude.

Haemoglobin levels are lower in elderly people, women and children.

1. Does exercise affect haemoglobin?
2. How are abnormally low haemoglobin levels treated?
3. Who is at high risk of abnormal haemoglobin levels?
4. Are there warning signs of low haemoglobin?
5. Can optimal haemoglobin levels be reached with a healthy, balanced diet?

1. Does exercise affect haemoglobin?
No, except for dehydration, which can temporarily raise haemoglobin levels.

2. How are abnormally low haemoglobin levels treated?
Treatment depends closely on the cause. Some types of anaemia are treated with iron, folic acid or vitamin B12, supported by B6.

3. Who is at high risk of abnormal haemoglobin levels?
Women of childbearing age may have temporary falls in haemoglobin during menstruation and pregnancy.

4. Are there warning signs of low haemoglobin?
Some warning signs are tiredness, weakness, pallor (loss of normal skin colour) and shortness of breath.

5. Can optimal haemoglobin levels be reached with a healthy, balanced diet?
A healthy diet including vegetables and iron-rich foods can be beneficial