HEMOGLOBIN (Hb) and Hemoglobin A1c test

HEMOGLOBIN (Hb) and Hemoglobin A1c test



Hemoglobin is the protein component of red blood cells that acts as a carrier for oxygen and carbon dioxide transport.  

It is an essential component of the blood and plays a crucial role in maintaining adequate oxygenation throughout the body.     

It is composed of heme (a pigment) that carries iron, and globin (a protein).

A hemoglobin test measures the amount of hemoglobin in your blood.

If your hemoglobin level is lower than normal, it means you have a low red blood cell count (anemia).

If a hemoglobin level is higher than normal, there are several potential causes of the blood disorder polycythemia vera, living at a high altitude, smoking, and dehydration.

When your hemoglobin level is low, it means your body isn’t getting enough oxygen, making you feel very tired and weak.

A severely low hemoglobin level for men is 13.5 gm/dL or lower.

For women, a severely low hemoglobin level is 12 gm/dL.

Hemoglobin tests are measured as part of a complete blood count (CBC).

Structure of Hemoglobin:

Hemoglobin consists of four protein subunits, each containing a heme group.

The heme group contains iron, which binds to oxygen molecules. Each hemoglobin molecule can bind up to four oxygen molecules.

Oxygen transport:

Hemoglobin facilitates the transport of oxygen from the lungs to the body tissues.

In the lungs, hemoglobin binds to oxygen, forming oxyhemoglobin.

When the blood reaches the tissues, oxyhemoglobin releases oxygen, which can then be utilized by the cells for various metabolic processes.

Clinical significance:

Measurement of hemoglobin levels is a crucial aspect of diagnosing and monitoring various medical conditions.

It helps assess oxygen-carrying capacity, evaluate anemia, determine the severity of blood loss, and monitor the response to treatment.


Hemoglobin levels are typically measured using a blood sample.

The most common method is a complete blood count (CBC), which provides information about various blood components, including hemoglobin concentration.

Hemoglobin levels are expressed in grams per deciliter (g/dL) or grams per liter (g/L) of blood.

The normal level of Hemoglobin

● Newborn: 14 to 24 g/dL or 140 to 240 g/L

● Infant One (1) week of age: 15 to 20 gm/dL

● Infant One (1) month of age: 11 to 15 gm/dL

● Children: 11 to 13 gm/dL

● Adult males: 14 to 18 gm/dL

● Adult women: 12 to 16 gm/dL

● Men after middle age: 12.4 to 14.9 gm/dL

● Women after middle age: 11.7 to 13.8 gm/dL

● Critical values: <5 g/dl or >20g/dl

Indications of Hemoglobin

To measure the severity of anemia or polycythemia and to monitor response to therapy.

Interpretation of Hemoglobin

● Low hemoglobin indicates anemia, characterized by an insufficient RBC count to deliver oxygen to peripheral tissues.

● High hemoglobin indicates polycythemia when the hemoglobin is more than 18.5g/dl in men and 16.5g/dl in women.

Increased Levels of Hemoglobin

Polycythemia vera


Chronic obstructive pulmonary disease

Congenital heart disease

Congestive heart disease


Decreased Levels of Hemoglobin


Nutritional deficiency

Bleeding from the digestive tract or bladder,

Heavy menstrual periods




Kidney disease



Liver disease



Low level of iron, folate, vitamin B12, or vitamin B6

Interfering Factors of Hemoglobin

Conditions that cause changes in plasma volume without changes in overall RBC cell count can also affect the Hb and may lead to relative anemia or relative polycythemia.

Nursing Implications of Hemoglobin

Manage fatigue

Maintain adequate nutrition

Maintain adequate perfusion and encourage patient compliance with prescribed therapy.

How to increase hemoglobin levels

Transfusing red blood cells

Receiving erythropoietin (a hormone used to stimulate red blood cell production in individuals with decreased red blood cell production or increased red cell destruction)

Taking iron supplements

Increasing the intake of iron-rich foods, such as eggs, spinach, artichokes, beans, lean meats, and seafood.

Increasing the intake of foods rich in cofactors, such as vitamin B6, folic acid, vitamin B12, and vitamin C.

Such foods include fish, vegetables, nuts, cereals, peas, and citrus fruits.


Hemoglobin A1c test

Hemoglobin A1c or glycosylated hemoglobin is a rough indication of blood sugar control in people with diabetes mellitus over the preceding 3 months.

As more glucose (blood sugar) circulates in the blood on a daily basis, is bound to the circulating hemoglobin.

Normal hemoglobin A1c levels range between 4% to 5.9%.

As this number reaches 6% or greater, it signifies poorer diabetes control.

Hemoglobin A1c of 6% roughly correlates with an average blood sugar level of 135 mg/dL (milligrams per deciliters) over the previous 3 months.

Each 1% increase in hemoglobin A1c above 6% represents an average blood sugar of approximately 35 mg/dL over 135 mg/dL

A hemoglobin A1c measurement of 7% corresponds to an average blood sugar level of 170 mg/dL in the previous 3 months.

Clinical considerations:

Hemoglobin levels are often evaluated alongside other blood parameters, such as hematocrit and red blood cell indices, to gain a comprehensive understanding of a person’s blood health.

Trends in hemoglobin levels over time, along with the individual’s symptoms and medical history, are important for diagnosis and monitoring of conditions.


The treatment for low hemoglobin levels depends on the underlying cause.

It may involve dietary changes, iron or vitamin supplementation, blood transfusions, or addressing the specific condition responsible for the anemia.

Treatment for high hemoglobin levels depends on the underlying cause and may include addressing the condition contributing to increased production or reducing blood thickness.

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