Hemoglobin Importance Within the Body

Hemoglobin has a critical role in your body. It's the protein in red blood cells (RBCs) that carries oxygen from your lungs to the tissues of your body. As such, abnormal levels of hemoglobin, or abnormal types of hemoglobin can result in serious disease.

Let's look at the normal ranges of hemoglobin in adults in children, conditions that cause either a low hemoglobin or a high hemoglobin level, and the tests for and significance of hereditary abnormal hemoglobins.


Hemoglobin is protein in red blood cells that is made up of four chains. Each of these chains contains a compound known as heme, which in turn contains iron, which is what transports oxygen in the bloodstream.

Hemoglobin is responsible for the shape of RBCs, which usually appear like donuts but with a thin center rather than a hole. In conditions involving abnormal hemoglobin, such as sickle cell anemia, the abnormal shape of the RBCs can lead to problems.

The pigment in hemoglobin is responsible for the red color of blood.


Hemoglobin functions by binding and transporting oxygen from the capillaries in the lungs to all of the tissues in the body. It also plays a role in the transport of carbon dioxide from the tissues of the body back to the lungs.

Nitric oxide and carbon monoxide are also able to bind with hemoglobin, with carbon monoxide binding much more readily than oxygen (the reason why carbon monoxide poisoning is so serious).

Conditions With Low Hemoglobin

A low hemoglobin level is referred to as anemia. Causes of anemia may include anything that interferes either with hemoglobin or the number of red blood cells present in the body.

With RBCs, in turn, there may be:

  • A loss (as in bleeding)
  • A lack of production in the bone marrow, either due to bone-marrow damage or tumor cells replacing the marrow
  • Break down in the bloodstream (called being "hemolyzed").

The many possible causes of a low hemoglobin include:

  • Blood loss: This may occur due to surgery, heavy menstrual periods, bleeding in the gastrointestinal tract, or any other form of bleeding. If you're premenopausal, you're more likely than men to have a low hemoglobin level due to the monthly loss of blood.
  • Lack of production: Lack of production of cells in the bone marrow may occur due to bone marrow failure (such as aplastic anemia), or infiltration of the bone marrow with cancer (such as with leukemias or lymphomas or solid tumors such as metastatic breast cancer).
  • Breakdown of red blood cells: Blood cells may be broken down (hemolyzed) in conditions such as hemolytic anemia.
  • Nutritional deficiency: An inadequate intake of iron (iron deficiency anemia), folic acid, or vitamin B12 (pernicious anemia).
  • Kidney disease
Risks of High and Low Hemoglobin Levels
Verywell / JR Bee

Conditions With Elevated Hemoglobin

Several conditions are associated with an elevated level of hemoglobin, including:

  • Lung diseases such as COPD and pulmonary fibrosis
  • Congenital (present at birth) heart disease
  • Right heart failure (cor pulmonale)

In many of these, the increased level is a compensatory mechanism to try to supply more oxygen to the body.

A hemoglobin level may be artificially elevated (only appear to be elevated) due to dehydration. Hemoglobin may also be "normally" elevated in people living at high altitudes.

Abnormal Hemoglobin

Conditions in which hemoglobin has an abnormal structure include:

  • Sickle cell anemia: An inherited condition in which the abnormal hemoglobin results in RBCs shaped like sickles. They can get "stuck" in blood vessels, resulting in a number of problems.
  • Thalassemia: Hereditary abnormal hemoglobins. Both alpha thalassemia and beta thalassemia have many different types, and symptoms vary from none to severe.

People with thalassemia often have life-long anemia and many require frequent transfusions. Thalassemia intermedia is also termed "non transfusion dependent thalassemia" and may not be discovered until adulthood.

Evaluating Hemoglobin Levels

A hemoglobin level is usually checked as a part of a complete blood count (CBC). When a doctor notes a low hemoglobin level, they also looks at other lab tests that may help determine the cause. These include:

  • Total red blood cell count
  • Red blood cell indices such as MCHC (mean corpuscular hemoglobin concentration), MCH (mean corpuscular hemoglobin), and MCV (mean corpuscular volume)
  • Serum ferritin level to check iron stores in the body

Normal Hemoglobin Ranges

Normal hemoglobin levels vary by age and sex. They're measured in grams per deciliter (g/dL).

  • Adult male: 13.8-17.2 g/dL
  • Adult female: 12.1-15.1 g/dL

A Word From Verywell

If you hear about hemoglobin, you may think of bleeding, especially heavy menstrual bleeding. Yet there is a wide range of disorders that can result in either an elevated or decreased hemoglobin. In addition, abnormal types of hemoglobin can contribute to disease.

In order to determine a cause of a low or high hemoglobin, your doctor will ask questions, perform a physical exam, and look at other blood tests in combination with your hemoglobin level.

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Article Sources
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