Hemoglobin Test
Reviewed
Also called: Hb, Hgb, H&H
A hemoglobin test measures the level of hemoglobin in your blood. Hemoglobin is an iron-rich protein in red blood cells that carries oxygen from your lungs to the rest of your body. The test is often used to check for anemia and is usually part of a complete blood count (CBC).
Specimen: Blood (from a vein in your arm)
Urgent safety information
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Why this test may be ordered
- As part of a routine exam
- If you have symptoms of anemia, such as weakness, dizziness, and cold hands and feet
- If you have a family history of thalassemia, sickle cell anemia, or other inherited blood disorder
- If you have a diet low in iron and other minerals
- If you have a long-term infection or excessive blood loss from an injury or surgical procedure
Preparation and collection
No special preparation is needed. If your provider has ordered other blood tests, you may need to fast for several hours beforehand.
A blood sample is taken from a vein in your arm using a small needle. The procedure usually takes less than five minutes.
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.
Understanding results
Your results will compare your hemoglobin level to the normal range (reference range). This range may vary based on the laboratory used and your age, race, and sex. The test cannot tell you what is causing an abnormal level, but knowing how high or low your level is can help your provider determine how severe your condition may be.
- Low hemoglobin level: Low hemoglobin levels may indicate your body does not have enough healthy red blood cells to carry oxygen to your tissues; possible causes include anemia, thalassemia, iron deficiency, liver disease, cancer, blood loss, or lack of certain nutrients. Limitation: The test cannot tell you what is causing a low level. Other factors (diet, medications, high altitude) can also affect results. Next step: Your provider may order additional tests to determine the cause and assess severity.
- High hemoglobin level: High hemoglobin levels may indicate your body is producing too many red blood cells or that your oxygen levels are low; possible causes include lung disease, heart disease, polycythemia vera, or sleep apnea. Limitation: The test cannot tell you what is causing a high level. Other factors (smoking, genetic conditions, high altitude) can also affect results. Next step: Your provider may order additional tests to determine the cause and whether treatment is needed.
- The test cannot tell you what is causing an abnormal level.
- Abnormal results do not always mean you have a medical condition that needs treatment.
- Results can be affected by diet, activity level, medications, dehydration, smoking, certain genetic conditions, and living at a high altitude.
What to do next
Talk with your provider about your results. Your provider will consider your symptoms, medical history, and other blood test results to understand your hemoglobin levels.
- Do you have symptoms of anemia such as weakness, dizziness, or cold hands and feet?
- Do you have a family history of thalassemia, sickle cell anemia, or other inherited blood disorders?
- Do you have a diet low in iron or other minerals?
- Do you have a long-term infection?
- Have you had excessive blood loss from an injury or surgical procedure?