Hemoglobin Importance Within the Body

Hemoglobin plays a vital role in your body. It's the protein in red blood cells (RBCs) that carries oxygen from your lungs to all of your tissues and organs. As such, any abnormalities of hemoglobin levels or structure can lead to serious symptoms.

Symptoms associated with hemoglobin abnormalities can include fatigue, rapid heart rate, pale skin, and more. If you have any of these problems, your healthcare provider will begin a diagnostic process to identify the cause and may order a hemoglobin test for you.


Hemoglobin is a protein made up of four amino acid chains. Each of these chains contains heme, a compound that contains iron and 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 can also bind with hemoglobin. Carbon monoxide binds to hemoglobin much more readily than oxygen, and its presence actually prevents oxygen from binding to hemoglobin. This is why carbon monoxide poisoning is so serious.

Conditions With Low Hemoglobin

A low hemoglobin level is often referred to as anemia. Causes of anemia may include anything that interferes either with the level or function of hemoglobin or RBCs.

Causes of 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. Premenopausal females are more likely to have a low hemoglobin level than men due to menstruation.
  • Lack of production: Diminished 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 leukemia, lymphoma, or solid tumors, such as metastatic breast cancer.
  • Hemolysis (breakdown of RBCs): Blood cells may be hemolyzed due to conditions such as severe infections, toxins, and malaria.
  • Nutritional deficiency: Iron deficiency, vitamin B12 deficiency, and folate deficiency can cause anemia.
  • Kidney disease: Healthy kidneys release erythropoietin, a hormone that promotes RBC production.
Risks of High and Low Hemoglobin Levels
Verywell / JR Bee

Conditions With Elevated Hemoglobin

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

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

In these cases, the increased hemoglobin is the result of the body's compensatory mechanism for low oxygen.

A hemoglobin test may show an artificially elevated hemoglobin level due to dehydration. In this situation, hemoglobin is more concentrated when the fluid in the body is low.

Hemoglobin may also be elevated in people living at high altitudes due to the oxygen in the atmosphere.

Abnormal Hemoglobin

Conditions in which hemoglobin has an abnormal structure include:

  • Sickle cell anemia: This is an inherited condition in which abnormal hemoglobin results in RBCs shaped like sickles. They can get "stuck" in blood vessels, resulting in pain, blood clots, and increased stroke risk.
  • Thalassemia: These hereditary diseases are characterized by different types of abnormal hemoglobin. 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 may require frequent blood 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 measured as a part of a complete blood count (CBC). The results of other lab tests may also help determine the cause of hemoglobin problems.

These include:

  • Total RBC count
  • Red blood cell indices such as MCHC (mean corpuscular hemoglobin concentration), MCH (mean corpuscular hemoglobin), and MCV (mean corpuscular volume)
  • Serum ferritin level, which measures 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 elevated or decreased hemoglobin. In addition, abnormal types of hemoglobin can contribute to disease.

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

Frequently Asked Questions

  • What are the signs that my red blood cell count is low?

    Fatigue is the number one sign. This is caused by anemia, a blood disorder resulting from a lack of hemoglobin, the essential protein found in red blood cells. Other symptoms may include headache, dizziness, weakness, pale skin, feeling cold, and trouble breathing.

  • Does exercising a lot cause anemia?

    Intense training, especially among endurance athletes, can cause a condition called “sports anemia.” It’s not the anemia that causes fatigue and requires iron supplements. Sports anemia refers to well-conditioned athletes’ relatively low hemoglobin levels, which result from an increased plasma volume. This has positive effects, enabling the blood to better circulate oxygen during exercise.

  • How do healthcare providers tell if you have a problem with your hemoglobin?

    A blood test called electrophoresis measures the types of hemoglobin in your blood and identifies abnormal hemoglobin including:

    • HgbS: Related to sickle cell disease
    • HgbC: Causes mild anemia
    • HgbE: Causes mild anemia 
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9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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