Summary :
Hemoglobin is a protein in your red blood cells that carries oxygen. The hemoglobin test is a common test that measures the amount of hemoglobin in your blood and is almost always done as part of a complete blood count (CBC).
◉ Introduction
Hemoglobin (Hb) is an iron-rich protein found in red blood cells (erythrocytes) and plays an essential role in transporting oxygen from the lungs to tissues and organs , thereby ensuring the proper functioning of various physiological processes.
Normal values of hemoglobin can indeed vary according to age, sex and other factors such as pregnancy or altitude. An abnormally low level of hemoglobin is generally called anemia.
The hemoglobin level in the blood is measured during a blood test called Complete Blood Count (CBC). To perform the test, a simple blood sample is taken, usually from the arm.
◉ Structure of hemoglobin
Hemoglobin is a tetrameric protein, meaning it is made up of four subunits, each with a polypeptide chain and a heme group that combine to form a functional structure .
- Protein subunits: In adults, there are two alpha-globin (α) chains and two beta-globin (β) chains, forming adult hemoglobin (HbA).
- The heme group is an organic compound that contains a central iron atom capable of bonding to an oxygen molecule.
- Each subunit of hemoglobin has an oxygen binding site where the heme iron atom binds to an oxygen molecule.
◉ Types
There are different types of hemoglobin that differ in their molecular composition. Hemoglobin electrophoresis is a test that measures the different types of hemoglobin in the blood.
The most commonly encountered types are:
- Hemoglobin A (HbA): This is the most abundant type of hemoglobin in adults. It is made up of two alpha-globin chains and two beta-globin chains.
- Fetal Hemoglobin (HbF): This type of hemoglobin is present in unborn babies and newborns. HbF levels gradually decrease to be replaced by HbA.
- Hemoglobin S (HbS): Associated with sickle cell disease, a genetic condition characterized by deformed (sickle-shaped) red blood cells and anemia.
- Hemoglobin C (HbC): Hemoglobin C, This type of hemoglobin does not transport oxygen well. It can cause mild to moderate anemia.
- Hemoglobin E (HbE): Associated with hemoglobinosis E, a genetic condition prevalent in Southeast Asia.
Note: There are many other hemoglobin variants and abnormalities (hemoglobinopathy) that may have specific medical implications.
◉ Hemoglobin function
- Oxygen Carrier: The main function of hemoglobin is to bind and transport oxygen from the lungs to the tissues of the body. It binds reversibly to oxygen, forming a complex called oxyhemoglobin.
- Carbon Dioxide Removal: Hemoglobin binds to carbon dioxide and transports it to the lungs, where it can be removed during exhalation.
- Hemoglobin also plays a role in the transport of nitric oxide (NO). Nitric oxide is a gas molecule that serves as a signaling molecule in various physiological processes.
◉ Hemoglobin assay
The monitoring and measurement of the hemoglobin level is usually done through laboratory blood tests called Complete Blood Count (CBC). The value of the result is usually expressed in Grams per deciliter (g/dL)
You do not need to be fasting for the exam. A healthcare professional will take a blood sample from your vein and send it to the lab where it will be tested.
◉ Normal level of hemoglobin in the blood
The amount of normal hemoglobin is included:
| Category | Hgb level, in grams per deciliter (g/dL) |
| Infants | 11-18 |
| Toddlers | 11.5-16.5 |
| Adult males | 13-16.5 |
| Adult females (non-pregnant) | 12-6 |
| Adult women (pregnant) | 11-16 |
Note: It is important to consider the specific reference values of the laboratory where the test was performed when interpreting hemoglobin results.
◉ Factors Affecting Hemoglobin Levels
Various factors influence hemoglobin levels in the body, including:
- Age: Hemoglobin levels are higher in newborns than in adults due to the high oxygen affinity of fetal hemoglobin compared to hemoglobin adult.
- Diet: Lack of iron in the diet is the leading cause of anemia. Therefore, ingestion of iron-rich foods, such as red meat, poultry, shellfish, dark leafy vegetables, and iron-fortified cereals, increases iron levels and subsequently increases iron levels. hemoglobin in the blood.
- Altitude: Because there is less air at high latitudes, the amount of hemoglobin in the blood of people there increases.
- Hydration: When dehydrated, the amount of plasma decreases. If the patient is well hydrated, hemoglobin and hematocrit will be higher than if the patient has normal plasma. Acute dehydration can increase the amount of hemoglobin in the blood by up to 10-15%.
- Pregnancy: it increases blood production by 30%. The production of hemoglobin requires more iron, causing anemia. Also, hemoglobin decreases during pregnancy due to the expansion of blood volume and the resulting dilution of red blood cells.
◉ Causes
2- Causes of low hemoglobin :
- Blood loss: Any type of blood loss can cause anemia
- Lack of production: Diseases of the bone marrow, such as aplastic anemia or leukemia, can disrupt the normal production of hematopoietic stem cells that give rise to red blood cells.
- Hemolysis
- Nutritional Deficiencies: Nutritional deficiencies can contribute to low hemoglobin: Deficiency of iron, vitamin B12, folate (vitamin B9), and vitamin C.
- Kidney disease: People with kidney disease may not produce enough erythropoietin (a hormone that promotes the production of red blood cells).
- Chronic diseases: Certain chronic diseases, such as cancer, autoimmune diseases or prolonged infections, can disrupt hemoglobin production.
2- Causes of High Hemoglobin :
If a hemoglobin test shows a higher than normal level, there are several potential causes:
- Smoking: Red blood cells and hemoglobin increase to compensate for the high levels of carbon monoxide in cigarette smoke.
- Living at high altitudes where there isn't as much oxygen in the air, like in the mountains.
- Heart or lung conditions that affect your ability to breathe, the ability of your lungs to pass oxygen into your bloodstream, or the ability of your heart to pump normally.
- Take erythropoietin EPO (example to improve high level physical performance).
- Being severely dehydrated.
- Chronically low oxygen levels.
- Polycythemia vera: A rare blood disorder often characterized by high hemoglobin levels due to excessive accumulation of red blood cells.
- Certain types of cancer (liver, kidney, etc.)
◉ Symptoms
1- What are the symptoms of low hemoglobin? :
- Fatigue and Weakness: Reduced oxygen-carrying capacity, leading to fatigue, weakness and decreased energy levels.
- Shortness of breath or rapid breathing: Inadequate supply of oxygen to the body can cause shortness of breath, especially during physical activity.
- Pale or sallow skin: Anemia can cause pale skin, mucous membranes and nails.
- Palpitations, rapid or irregular heartbeat: The heart may beat faster to compensate for reduced oxygen levels.
- Coldness in the extremities (cold hands and feet)
- Headaches, dizziness and dizziness: Insufficient oxygen supply to the brain can lead to headaches and dizziness.
- Difficulty concentrating or remembering
- Fragility of nails and hair
2- High Hemoglobin Symptoms :
If your hemoglobin level is higher than usual, you may experience the following symptoms:
- Increased blood viscosity: High hemoglobin levels can lead to thicker blood, making it harder for the heart to pump blood through the vessels.
- High Blood Pressure: Higher blood viscosity may contribute to increased blood pressure.
- Increased risk of blood clots: thicker blood can increase the risk of blood clots, which can lead to deep vein thrombosis, stroke or heart attack.
- Excessive sweating (hyperhidrosis)
- Headaches and dizziness: Thickened blood flow can impair the oxygen supply to the brain, causing headaches and dizziness.
- Redness or abnormal flushing of the skin: Polycythemia can cause a reddish appearance due to the increased concentration of red blood cells.
- Easy bruising or bleeding.
- Symptoms of the underlying condition leading to increased levels (which may vary)
- Unexplained weight loss.
- Swollen joints.
◉ Additional tests
To make an accurate diagnosis and implement appropriate treatment in the event of abnormally low hemoglobin levels, the healthcare professional may request several other complementary tests
- Red blood cell count: Assess the total number of red blood cells in the blood.
- MCV Blood Test: allows you to assess the average size of red blood cells and to differentiate between microcytic, normocytic and macrocytic anemias.
- Reticulocytes levels: assesses the ability of the bone marrow to produce new red blood cells
- Ferritinemia: assesses iron stores in the body.
- Dosage of vitamin B12 and folic acid.
- Transferrin saturation.
- Liver and kidney tests.
◉ Treatment
The treatment depends on the hemoglobin level in the blood, the cause and the symptoms that the patient has:
- In anemia caused by iron deficiency, treatment may involve iron supplementation or iron therapy to replenish iron stores and stimulate red blood cell production.
- If the cause of abnormal hemoglobin levels is related to other nutrient deficiencies or chronic diseases, treatment may involve treating those specific deficiencies or managing the underlying condition accordingly.
- In more severe cases or specific hemoglobin disorders, such as thalassemia or sickle cell disease, specialist treatments may be required.
- Therapies may include regular blood transfusions to maintain appropriate levels or specialized medications to manage the symptoms and complications associated with these disorders.
◉ Conclusion
Hemoglobin is an essential protein responsible for transporting oxygen in the body. Its ability to bind and release oxygen ensures the supply of oxygen to all tissues and organs, promoting their proper functioning.
Regular monitoring of hemoglobin levels and understanding the factors influencing its levels are essential for diagnosing and managing various health conditions.