Haemoglobin Test: Why and How is it Done?

What is the Haemoglobin Test?

The Haemoglobin test, abbreviated as Hb test or Hgb blood test, measures the level of haemoglobin in the human bloodstream. Haemoglobin refers to the protein carried by the red blood cells (RBCs). It specialises in absorbing oxygen in the lungs and then carrying it to the peripheral tissues throughout the body. This helps in maintaining the viability of cells. 

Haemoglobin is produced from two types of proteins known as alpha and beta. These are of the same kind and stick to each other. The presence of both these proteins is essential for the haemoglobin to absorb and release oxygen as expected. The beta protein does not get expressed until birth. Another protein called gamma acts as its substitute during foetal development and exists only till the birth of the baby. A low level of haemoglobin below the acceptable limit may indicate a blood disorder owing to iron deficiency.

Why is the Haemoglobin Test Done?

The objective of the haemoglobin test is to analyse the level of haemoglobin in your blood. It can be suggested as a part of a routine health check-up or when the doctor suspects the presence of a blood disorder that is affecting your red blood cells. The Hb test evaluates whether the haemoglobin level is normal or beyond the acceptable limits. 

In case it is below or above the acceptable range, it assesses the severity of blood disorders like anaemia, polycythaemia and monitors the response to treatment. Anaemia implies that the level of red blood cells is below normalcy, indicating various medical conditions that may even be life-threatening. The lower the haemoglobin level, the greater will be the severity of the blood disorder. 

The haemoglobin test may be advised along with other blood tests to patients with blood disorders like anaemia and polycythaemia. These blood tests include:

• Haematocrit – This analyses the percentage of RBCs in the human blood.
• Complete blood count – This evaluates the type and number of cells in the blood.

A thorough and comprehensive screening for anaemia should combine the cutoff values of all the three tests – Hb, haematocrit, and HCT. This is necessary for an accurate diagnosis of iron deficiency and blood disorders. It is also necessary to evaluate the eligibility of blood donation and make decisions regarding blood transfusion.

The health conditions and lifestyle habits that these tests help in diagnosing are as below:

• Anaemia that manifests through symptoms like weakness, pale skin, dizziness, cold limbs, etc.
• A genetic history of inherited blood disorders like sickle cell anaemia and thalassemia
• A chronic infection anywhere in the body
• Excessive loss of blood due to surgery or injury
• An iron-deficient diet

Read More : HbA1c Test: Why and How is it Done?

Prerequisites for the Haemoglobin Test

There are no special preparations required to be followed before undergoing the haemoglobin test, unless specified otherwise by your doctor. Some tests need overnight fasting but this is usually not applicable for the haemoglobin test.

Make sure that you discuss the medications that you may be taking now or in the recent past. These medications include OTC (over-the-counter) medications, prescription medications, vitamins, supplements, herbals, and also illicit drugs that you may be taking. This is because there may be some medications that react with your haemoglobin and alter the result of your Hgb blood test. Your doctor will guide you in case of any preparations that you may need before the test.

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Understanding the Results of the Haemoglobin Test

The results of the hemoglobin test can be of two types:

• Anaemia or low haemoglobin, and
• Polycythaemia or high haemoglobin

The normal level of haemoglobin varies on the basis of gender, age, and other factors like reproductive age of women. Below are the normal ranges for Hb test:

Low haemoglobin may indicate one of the below medical conditions:

• Iron deficiency
• Anaemia
• Thalassaemia
• Cancer
• Liver disorders

High haemoglobin may indicate the below health conditions:

• Heart diseases
• Lung disorders
• Polycythemia vera, a condition that arises when the body produces more red blood cells than required. The common symptoms are weakness and fatigue, headaches and breathlessness.

However, abnormal levels of haemoglobin, that is, low or high haemoglobin, does not necessarily imply a serious medical condition that needs to be treated. It can occur due to monthly menstrual cycle in women and/or the result of iron-deficient diet and other lifestyle habits. A daily diet rich in iron, regular physical activities, and iron supplements are usually effective in maintaining the normal level of haemoglobin. 

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When should the Haemoglobin Test be Repeated?

The haemoglobin test is usually repeated at regular intervals to assess the level of haemoglobin. For evaluation of certain medical conditions or to monitor the treatment of some medical conditions, the doctor may advise repeating the test regularly. Follow the doctor’s advice.

Procedure for the Haemoglobin Test

For the Hb test, a blood sample is drawn from any of the following parts of the body:

• Vein for children and adults
• Fingerstick for children and adults, or
• Heelstick for newborns

The healthcare expert selects the location from where he/she will draw blood and applies an antiseptic solution to clean the area. The needle is then inserted into the vein to draw blood, which is then collected in the vial of the injection. A cotton swab is used to soak the blood from the puncture and then covered with a bandage. The entire process usually does not take more than 5 minutes. The bandage can be disposed of after about 10 minutes or as advised by the healthcare expert. The blood sample is sent to a laboratory for microscopic analysis to evaluate the haemoglobin level.