Hemoglobin

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Hemoglobin

Overview

Risks

Results

Hemoglobin

Definition:

A hemoglobin test measures the total amount of hemoglobin in the blood. Hemoglobin is almost always ordered as part of a complete blood count (CBC). See also Hemoglobin electrophoresis.

Alternative Names:
Hgb; Hb
How the test is performed:

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Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins to fill with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children:

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test:

No special preparation is necessary.

In infants and children:

The preparation you can provide for this test depends on your child's age, interests, previous experiences, and level of trust. For more information on how you can prepare children for lab tests, see the following topics:

infant test or procedure preparation (birth to 1 year)
toddler test or procedure preparation (1 to 3 years)
preschooler test or procedure preparation (3 to 6 years)
schoolage test or procedure preparation (6 to 12 years)
adolescent test or procedure preparation (12 to 18 years)

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

Hemoglobin is the protein that carries oxygen in the blood. It is contained in red blood cells. Both high and low hemoglobin counts indicate defects in the balance of red blood cells in the blood, and may indicate disease.