What is a Hemoglobin Test?

A hemoglobin test measures the levels of hemoglobin in your blood. Hemoglobin is an iron-rich protein in your red blood cells. It carries oxygen from your lungs to the rest of your body. Your cells need oxygen to grow, reproduce, and make energy for you to function. Your hemoglobin levels provide information about the health of your red blood cells. If your hemoglobin levels are abnormal, it may be a sign that you have a blood disorder.

Other names: Hb, Hgb, H&H

What is it used for?

A hemoglobin test is a blood test often used to check for anemia, a condition in which your body does not make enough healthy red blood cells. If you have anemia, the cells in your body don't get all the oxygen they need. Hemoglobin levels are usually measured as part of a complete blood count (CBC). A CBC is a group of tests that measure the number and type of cells in your blood.

A hemoglobin test is not the same as a hemoglobin A1C test. The A1C test is used to check your average blood glucose (blood sugar).

Why do I need a hemoglobin test?

Your health care provider may order the test as part of a routine exam, or if you have:

• Symptoms of anemia, which include weakness, dizziness, and cold hands and feet
• A family history of thalassemia, sickle cell anemia, or other inherited blood disorder
• A diet low in iron and other minerals
• A long-term infection
• Excessive blood loss from an injury or surgical procedure

You may also need this test to monitor the treatment of anemia or the other health conditions that could affect your hemoglobin level.

What happens during a hemoglobin test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You don't need any special preparation for a hemoglobin test. If your provider has ordered other blood tests, you may need to fast (not eat or drink) for several hours before the test. Your provider will let you know if there are any special instructions.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

Your results will compare your hemoglobin level to the normal range, which may be called the reference range. This range may vary, based on the laboratory used and your age, race, and sex. The test can't tell you what's causing an abnormal level. But knowing how high or low your hemoglobin level is can help your provider determine how severe your condition may be.

Your hemoglobin levels may not be in the reference range for many reasons.

Low hemoglobin levels may be a sign of:

• Different types of anemia
• Thalassemia
• Iron deficiency
• Liver disease
• Cancer and other diseases
• Blood loss from injury, a heavy menstrual period, or other problems
• Lack of certain nutrients, such as iron or vitamin B-12

High hemoglobin levels may be a sign of:

• Lung disease
• Heart disease
• Polycythemia vera, a disease which causes your bone marrow to make too many red blood cells
• Sleep apnea, a disorder that causes you to repeatedly stop breathing during sleep

If any of your levels are abnormal, it doesn't always mean you have a medical condition that needs treatment. Living at a higher altitude can also cause a high hemoglobin level. Other factors that can affect your results can include:

• Diet
• Activity level
• Certain medicines
• Dehydration
• Smoking
• Certain genetic conditions

Talk with your provider if you have questions about your results. To understand your hemoglobin results, your provider will also consider your symptoms, medical history, and the results of other blood tests.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about a hemoglobin test?

Some forms of anemia are mild, while other types of anemia can be serious and even life threatening if not treated. If you are diagnosed with anemia, talk to your provider about the best treatment plan for you.