Hemoglobin
Hgb; Hb; Anemia - Hb; Polycythemia - HbHemoglobin is a protein in red blood cells that carries oxygen. The hemoglobin test measures how much hemoglobin is in your blood.
How the Test is Performed
A blood sample is needed.
Blood sample
Venipuncture is the collection of blood from a vein. It is most often done for laboratory testing.

How to Prepare for the Test
No special preparation is necessary.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the Test is Performed
The hemoglobin test is a common test and is almost always done as part of a complete blood count (CBC). Reasons or conditions for ordering the hemoglobin test include:
Complete blood count
A complete blood count (CBC) test measures the following:The number of red blood cells (RBC count)The number of white blood cells (WBC count)The tota...

- Symptoms such as fatigue, poor health, or unexplained weight loss
- Signs of bleeding
- Before and after major surgery
- During pregnancy
- Chronic kidney disease or many other chronic medical problems
- Monitoring of anemia and its cause
- Monitoring during treatment for cancer
- Monitoring medicines that may cause anemia or low blood counts
Normal Results
Normal results for adults vary, but in general are:
- Male: 13.8 to 17.2 grams per deciliter (g/dL) or 138 to 172 grams per liter (g/L)
- Female: 12.1 to 15.1 g/dL or 121 to 151 g/L
Normal results for children vary, but in general are:
- Newborn: 14 to 24 g/dL or 140 to 240 g/L
- Infant: 9.5 to 13 g/dL or 95 to 130 g/L
The ranges above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your health care provider about the meaning of your specific test results.
What Abnormal Results Mean
LOWER THAN NORMAL HEMOGLOBIN
Low hemoglobin level may be due to:
- Anemia caused by red blood cells dying earlier than normal (hemolytic anemia)
Hemolytic anemia
Anemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to body tissues. Normally, red ...
ImageRead Article Now Book Mark Article - Anemia (various types)
- Bleeding from digestive tract or bladder, heavy menstrual periods
Bleeding from digestive tract
Gastrointestinal (GI) bleeding refers to any bleeding that starts in the gastrointestinal tract. Bleeding may come from any site along the GI tract, ...
ImageRead Article Now Book Mark Article - Chronic kidney disease
- Bone marrow being unable to produce new red blood cells. This may be due to leukemia, other cancers, drug toxicity, radiation therapy, infection, or bone marrow disorders
Leukemia
Leukemia is a type of blood cancer that begins in the bone marrow. Bone marrow is the soft tissue in the center of the bones, where blood cells are ...
ImageRead Article Now Book Mark Article - Poor nutrition (including low level of iron, folate, vitamin B12, or vitamin B6)
Poor nutrition
Malnutrition is the condition that occurs when your body does not get enough nutrients.
ImageRead Article Now Book Mark Article - Low level of iron, folate, vitamin B12, or vitamin B6
Folate
Folic acid and folate are both terms for a type of B vitamin (vitamin B9). Folate is a B vitamin that occurs naturally in foods such as green leafy v...
ImageRead Article Now Book Mark ArticleVitamin B12
Vitamin B12 is a water-soluble vitamin. Water-soluble vitamins dissolve in water. After the body uses these vitamins, leftover amounts leave the bo...
ImageRead Article Now Book Mark ArticleVitamin B6
Vitamin B6 is a water-soluble vitamin. Water-soluble vitamins dissolve in water so the body cannot store them. Leftover amounts of the vitamin leav...
ImageRead Article Now Book Mark Article - Other chronic illness, such as rheumatoid arthritis
HIGHER THAN NORMAL HEMOGLOBIN
High hemoglobin level is most often caused by low oxygen levels in the blood (hypoxia), present over a long period of time. Common reasons include:
- Certain birth defects of the heart that are present at birth (congenital heart disease)
Congenital heart disease
Congenital heart disease (CHD) is a problem with the heart's structure and function that is present at birth.
ImageRead Article Now Book Mark Article - Failure of the right side of the heart (cor pulmonale)
Cor pulmonale
Cor pulmonale is a condition that causes the right side of the heart to fail. Long-term high blood pressure in the arteries of the lung and right ve...
ImageRead Article Now Book Mark Article - Severe chronic obstructive pulmonary disease (COPD)
- Scarring or thickening of the lungs (pulmonary fibrosis) and other severe lung disorders
Pulmonary fibrosis
Idiopathic pulmonary fibrosis (IPF) is scarring or thickening of the lungs without a known cause.
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Other reasons for high hemoglobin level includes:
- A rare bone marrow disease that leads to an abnormal increase in the number of blood cells (polycythemia vera)
Polycythemia vera
Polycythemia vera (PV) is a bone marrow disease that leads to an abnormal increase in the number of blood cells. The red blood cells are mostly affe...
Read Article Now Book Mark Article - The body having too little water and fluids (dehydration)
Risks
There is little risk involved with having your blood taken.Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Multiple punctures to locate veins
- Hematoma (blood buildup under the skin)
- Infection (a slight risk any time the skin is broken)
References
Chernecky CC, Berger BJ. Hemoglobin (HB, Hgb). In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. Philadelphia, PA: Elsevier; 2013:621-623.
Marcdante KJ, Kliegman RM. Hematology assessment. In: Marcdante KJ, Kliegman RM, eds. Nelson Essentials of Pediatrics. 8th ed. Elsevier; 2019:chap 149.
Means RT. Approach to the anemias. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 149.
Hemoglobin - illustration
Hemoglobin is the most important component of red blood cells. It is composed of a protein called heme, which binds oxygen. In the lungs, oxygen is exchanged for carbon dioxide. Abnormalities of an individual's hemoglobin value can indicate defects in the normal balance between red blood cell production and destruction. Both low and high values can indicate disease states.
Hemoglobin
illustration
Hemoglobin - illustration
Hemoglobin is the most important component of red blood cells. It is composed of a protein called heme, which binds oxygen. In the lungs, oxygen is exchanged for carbon dioxide. Abnormalities of an individual's hemoglobin value can indicate defects in the normal balance between red blood cell production and destruction. Both low and high values can indicate disease states.
Hemoglobin
illustration
Review Date: 1/13/2020
Reviewed By: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.