FAQ ON HAEMOGLOBIN (HGB) COUNT AND ITS CLINICAL SIGNIFICANCE
WHAT IS HAEMOGLOBIN (HGB), AND WHY IS IT IMPORTANT IN A FULL BLOOD COUNT (FBC)?
Haemoglobin (HGB) is a protein found in red blood cells that is essential for carrying oxygen from the lungs to the rest of the body and returning carbon dioxide back to the lungs for exhalation. Haemoglobin gives red blood cells their characteristic red colour and plays a vital role in maintaining the body’s oxygen balance. In a Full Blood Count (FBC), the haemoglobin count is a critical measure because it reflects the blood's ability to carry oxygen. Doctors use haemoglobin levels to assess whether the body is receiving sufficient oxygen and to identify potential problems like anaemia, polycythaemia, or other blood disorders.
WHAT IS THE NORMAL RANGE FOR HAEMOGLOBIN COUNT IN AN FBC?
The normal range for haemoglobin count varies slightly depending on factors such as age, gender, and overall health. For adult men, the normal range is typically between 13.8 and 17.2 grams per decilitre (g/dL) of blood. For adult women, the normal range is usually between 12.1 and 15.1 g/dL. These ranges may vary slightly depending on the laboratory's reference values. It’s also important to consider that factors like pregnancy can naturally lower haemoglobin levels, while higher altitudes can lead to increased levels as the body adapts to lower oxygen availability.
WHAT DOES A LOW HAEMOGLOBIN COUNT (ANAEMIA) INDICATE?
A low haemoglobin count, known as anaemia, indicates that your blood is not carrying enough oxygen to your body’s tissues. Anaemia can have many causes, including nutritional deficiencies, such as a lack of iron, vitamin B12, or folate, which are essential for red blood cell production. Iron-deficiency anaemia is the most common type and occurs when there is not enough iron to produce sufficient haemoglobin.
Chronic diseases, such as kidney disease or chronic inflammatory conditions, can also lead to anaemia. The kidneys produce a hormone called erythropoietin, which stimulates red blood cell production. When the kidneys are not functioning properly, this hormone production may decrease, leading to lower haemoglobin levels. Blood loss, whether from injury, surgery, or internal bleeding, can also cause a reduction in haemoglobin. Additionally, certain genetic conditions, such as thalassaemia or sickle cell disease, affect the production or structure of haemoglobin, leading to anaemia. Symptoms of anaemia often include fatigue, weakness, dizziness, and shortness of breath due to the reduced oxygen-carrying capacity of the blood.
WHAT DOES A HIGH HAEMOGLOBIN COUNT (POLYCYTHAEMIA) INDICATE?
A high haemoglobin count, known as polycythaemia, indicates that there are more red blood cells than normal in the blood, which can thicken the blood and increase the risk of clots, stroke, and heart attack. One common cause of polycythaemia is dehydration, where the loss of body fluids leads to a higher concentration of red blood cells and haemoglobin in the blood.
Another cause of polycythaemia is living at high altitudes, where the air contains less oxygen. In response, the body produces more red blood cells and haemoglobin to ensure that enough oxygen is delivered to the tissues. This condition, known as secondary polycythaemia, is a normal adaptation to low oxygen levels. However, polycythaemia can also be caused by more serious conditions, such as polycythaemia vera, a type of blood cancer where the bone marrow produces too many red blood cells. Other causes include chronic lung disease and heart disease, where the body tries to compensate for reduced oxygen levels by increasing haemoglobin production.
HOW DOES THE HAEMOGLOBIN COUNT RELATE TO OTHER FBC PARAMETERS?
The haemoglobin count is closely related to other parameters in the Full Blood Count (FBC), such as the red blood cell (RBC) count, haematocrit, and red cell indices like mean corpuscular volume (MCV) and mean corpuscular haemoglobin (MCH). The RBC count measures the number of red blood cells in your blood, while the haematocrit indicates the proportion of your blood that is made up of red blood cells. Both RBC count and haematocrit are often correlated with haemoglobin levels. For example, if your haemoglobin level is low, it’s likely that your RBC count and haematocrit will also be low, indicating anaemia.
Red cell indices provide further insight into the characteristics of your red blood cells. The mean corpuscular volume (MCV) measures the average size of your red blood cells, while the mean corpuscular haemoglobin (MCH) indicates the average amount of haemoglobin in each red blood cell. These indices help doctors determine the type of anaemia and its cause. For example, low MCV and MCH values suggest microcytic, hypochromic anaemia, which is often due to iron deficiency. High MCV may indicate macrocytic anaemia, which can be caused by vitamin B12 or folate deficiency.
WHAT IS THE SIGNIFICANCE OF HAEMOGLOBIN LEVELS IN CLINICAL PRACTICE?
Haemoglobin levels are a key indicator of your overall health and are used in clinical practice to diagnose and monitor a variety of conditions. Low haemoglobin levels can indicate anaemia, which requires further investigation to determine the underlying cause. Depending on the cause, treatment may involve dietary changes, supplements, or addressing underlying conditions such as kidney disease or chronic blood loss.
High haemoglobin levels can indicate polycythaemia, which might require treatments to reduce the risk of complications like blood clots. This might include therapeutic phlebotomy (removing blood from the body), medication to reduce red blood cell production, or treating the underlying cause, such as improving oxygenation in lung disease. Regular monitoring of haemoglobin levels is essential for managing chronic conditions that affect blood production or oxygen transport, and it helps doctors adjust treatment plans as needed.
CAN HAEMOGLOBIN LEVELS FLUCTUATE, AND WHAT FACTORS INFLUENCE THESE FLUCTUATIONS?
Yes, haemoglobin levels can fluctuate due to a variety of factors. Dehydration can cause a temporary increase in haemoglobin levels by reducing plasma volume, making the blood more concentrated. Conversely, overhydration can dilute the blood, leading to a lower haemoglobin level. Physical activity can also temporarily increase haemoglobin levels as the body demands more oxygen, prompting a rise in red blood cell production.
Living at high altitudes is another factor that can increase haemoglobin levels, as the body adapts to the lower oxygen levels by producing more red blood cells. Smoking is also known to increase haemoglobin levels due to the body’s attempt to compensate for the reduced oxygen levels caused by carbon monoxide from cigarette smoke. Certain medications, such as erythropoiesis-stimulating agents used in chronic kidney disease, can also influence haemoglobin levels by stimulating red blood cell production.
