Table of ContentsView AllTable of ContentsFunctionLow HemoglobinElevated HemoglobinAbnormal HemoglobinEvaluating LevelsFrequently Asked Questions
Table of ContentsView All
View All
Table of Contents
Function
Low Hemoglobin
Elevated Hemoglobin
Abnormal Hemoglobin
Evaluating Levels
Frequently Asked Questions
Hemoglobinis an iron-containing protein inred blood cells (RBCs)that gives blood its red color. It has two primary functions: It transfers oxygen from your lungs to tissues throughout your body, and it carries carbon dioxide from cells back to the lungs so it can be expelled.
When hemoglobin is too low, it can indicate certaintypes of anemia. There are also abnormal types of hemoglobin that cause anemia as well as illnesses such assickle cell disease.
This article explains the functions of hemoglobin in your body. It also looks at some of the conditions associated with high and low hemoglobin.
Verywell / JR Bee
The Function of Hemoglobin
Hemoglobin binds and transports oxygen from the lungs to the tissues in the body. It also transports carbon dioxide from tissues back to the lungs.
Nitric oxide and carbon monoxide can also bind with hemoglobin. Carbon monoxide binds to hemoglobin much more strongly than oxygen. Its presence keeps oxygen from binding to hemoglobin. This is whycarbon monoxide poisoningis so serious.
Hemoglobin contains around 70% of the iron in your body and gives red blood cells their distinctive red color.
Structure and Abnormalities
There are several different types of hemoglobin, the two most common of which are:
There are abnormal types of hemoglobin that affect both the shape of RBCs but also their ability to transport oxygen and carbon dioxide, including:
RBCs usually look like donuts, but with a thin center instead of a hole.
Conditions Involving Low Hemoglobin
Causes of anemia include:
Blood Loss
Any type ofblood losscan cause anemia. This includes:
Premenopausal females are more likely to have a low hemoglobin level than males.
The Different Types of Anemia
Lack of Production
In some conditions, thebone marrowmay not produce enough RBCs. These conditions include:
Hemolysis
Hemolysisis the breakdown of RBCs. This may happen with conditions like:
Understanding the Many Types of Hemolytic Anemia
Nutritional Deficiencies
Certain nutritional deficiencies can cause anemia. These include:
Kidney Disease
Healthy kidneys releaseerythropoietin. This is a hormone that promotes RBC production. People withkidney diseasemay not produce enough of this hormone.
Conditions Involving Elevated Hemoglobin
Several conditions are associated withhigh hemoglobin levels. These include:
If you aredehydrated, yourhemoglobin testmay show an artificially high hemoglobin level. This is because hemoglobin is more concentrated when the fluid in the body is low.
Hemoglobin may also be high in people living at high altitudes. This is because of the low levels of oxygen in the air.
Recognizing Dehydration
Conditions with Abnormal Hemoglobin
Conditions where hemoglobin has an abnormal structure include:
Sickle Cell Anemia
Sickle cell anemia is an inherited condition. In people with this condition, abnormal hemoglobin causes sickle-shaped RBCs. These cells can get “stuck” in blood vessels. This can cause:
Thalassemia
Alpha thalassemiaandbeta thalassemiaare the two main types. There are also many different subtypes. Symptoms vary from none to severe.
People with thalassemia often have lifelong anemia. They may require frequentblood transfusions.
Thalassemia intermediais also called “non-transfusion-dependent thalassemia.” This kind of thalassemia may not be discovered until adulthood.
RecapConditions like sickle cell anemia and thalassemia can cause hemoglobin to have an abnormal structure.
Recap
Conditions like sickle cell anemia and thalassemia can cause hemoglobin to have an abnormal structure.
Hemoglobin Tests
Hemoglobin levels are usually measured as part of acomplete blood count (CBC). The results of other lab tests may help identify the cause of hemoglobin problems. These include:
Normal Hemoglobin Levels
Summary
Hemoglobin is a protein in red blood cells that carries oxygen from your lungs to your tissues. Problems with hemoglobin can cause symptoms like fatigue and rapid heart rate.
Hemoglobin levels that are too high or too low can lead to health problems. In conditions like sickle cell anemia, hemoglobin can have an abnormal shape. This can lead to serious problems like pain and blood clots.
Hemoglobin levels are usually checked as part of a complete blood count. Other lab tests can help confirm the cause of hemoglobin issues.
A Word From Verywell
—STEFFINI STALOS, DO, MEDICAL EXPERT BOARD
Learn MoreWhat to Expect if You Have Anemia
A blood test calledelectrophoresismeasures the types of hemoglobin in your blood. This test identifies abnormal hemoglobin including:HgbS: Related to sickle cell diseaseHgbC: Causes mild anemiaHgbE: Causes mild anemia
A blood test calledelectrophoresismeasures the types of hemoglobin in your blood. This test identifies abnormal hemoglobin including:
9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
MedlinePlus.Hemoglobin electrophoresis.
University of Rochester Medical Center. Health Encyclopedia.What are red blood cells?
Karakochuk CD, Hess SY, Moorthy D, et al.Measurement and interpretation of hemoglobin concentration in clinical and field settings: a narrative review.Ann N Y Acad Sci. 2019;1450(1):126-146. doi:10.1111/nyas.14003
MedlinePlus.Hemoglobin test.
MedlinePlus.Thalassemia.
MedlinePlus.RBC indices.
Cleveland Clinic.Low hemoglobin.
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