What is a hemoglobin test?
A hemoglobin test measures the amount of hemoglobin in your blood. Hemoglobin is a protein that’s the main component of red blood cells (erythrocytes). Hemoglobin contains iron, which allows it to bind to oxygen. Hemoglobin enables your red blood cells to carry oxygen from your lungs to other tissues and organs throughout your body.
The amount of hemoglobin you have, or your hemoglobin levels, provides clues about how healthy your red blood cells are. Knowing your hemoglobin level can help a healthcare provider diagnose blood disorders and other conditions. Hemoglobin tests are commonly used to diagnose anemia, which involves not having enough hemoglobin or healthy red blood cells.
Why is a hemoglobin test done?
Your provider may perform a hemoglobin test as part of a routine physical exam. Hemoglobin tests are part of a complete blood count (CBC) test, which identifies the number of red blood cells, white blood cells and platelets in a blood sample. This information allows your provider to assess your health and screen for certain conditions.
Your provider may also perform a hemoglobin test if you have symptoms that suggest conditions related to low hemoglobin levels or high hemoglobin levels.
Having low hemoglobin or too few red blood cells (RBC) can deprive your tissues and organs of the oxygen they need to make energy and keep you healthy.
Symptoms of low hemoglobin include:
- Pale skin (pallor).
- Shortness of breath.
- Cold hands and feet.
Having high hemoglobin or too many red blood cells can cause your blood to thicken and become sluggish. Thick blood doesn’t flow as quickly, depriving your organs of oxygen.
Symptoms of high hemoglobin include:
- Blurred or double vision.
- Blood clots.
Finally, your provider may check your hemoglobin to see how you respond to treatments meant to lower or boost your red blood cell count.
How do I prepare for a hemoglobin test?
A hemoglobin test doesn’t require any special preparation. It only takes a few minutes. You can get tested in your provider’s office, a medical laboratory or another outpatient setting.
In some instances, a hemoglobin test occurs alongside other blood tests that will require you to fast (no food or drink) for a specific time before the test. Follow your provider’s instructions so you’re prepared.
How is a hemoglobin test done?
Your healthcare provider will take a blood sample from your arm or hand. They can also draw blood using a finger prick. A heel stick may be used for newborns or infants.
First, your provider will swab your skin with alcohol. They’ll place an elastic band around your upper arm and ask you to make a fist to make the blood flow easier. Then, they’ll insert a small needle into a vein. You may feel a sting when the needle’s inserted. Your blood will flow from the needle into a vial.
Finally, your provider will send the vial to a lab for analysis.
What are the risks of a hemoglobin test?
Blood tests don’t involve many risks. You may experience slight pain during the blood draw, and the site may appear bruised or swollen for a few days. These symptoms usually go away on their own.
Results and Follow-Up
What do the test results mean?
A hemoglobin test can show if your levels are too low, as with anemia, or too high. It can also show how severe your condition is. It can’t detect what’s causing your abnormal levels.
Your healthcare provider will consider your hemoglobin levels alongside other test results to make a diagnosis.
What level of hemoglobin is normal?
The normal range for hemoglobin levels is 12 grams per deciliter to 17.4 grams per deciliter of blood for adults. However, levels may vary depending on your age, race and sex.
Factors related to your lifestyle and environment can also cause you to have abnormal levels, including:
- Your diet.
- Exercise or physical activity.
- Medications you’re taking.
What do low hemoglobin levels mean?
Lower than normal hemoglobin levels, or anemia, may be a sign that your body isn’t producing enough red blood cells. Low levels may also signal that your red blood cells are being destroyed faster than they’re made (hemolytic anemia). Chronic (long-lasting) blood loss also leads to a drop in hemoglobin levels. It’s one of the most common causes of anemia.
Low hemoglobin levels may be a sign of:
- An iron deficiency.
- A nutrient deficiency (for example, vitamin B12 or folic acid).
- Cancers that affect your blood or bone marrow.
- Kidney disease.
- Liver disease.
- Sickle cell disease.
- Autoimmune diseases.
- Blood loss resulting from surgery, injury, menstrual bleeding or bleeding from your gastrointestinal tract.
What do high hemoglobin levels mean?
Some conditions increase your number of red blood cells, causing too much hemoglobin in your blood. If you’re dehydrated, your hemoglobin may be high because you have too many red blood cells in relation to your blood volume.
High hemoglobin levels may be a sign of:
- Polycythemia vera.
- Congenital heart defects.
- Certain types of kidney diseases, including kidney cancer.
- Lung disease, including chronic pulmonary obstructive disease (COPD) and pulmonary fibrosis.
What follow-up is required?
Your healthcare provider will discuss the results with you if they’re concerned there’s a problem. They may order more tests, depending on the results. Treatment will depend on what’s causing your abnormal levels. Discuss treatment options with your provider. You may have to have hemoglobin tests regularly if you’re receiving treatment for a blood disorder.
What is the difference between a hemoglobin test and a hemoglobin a1c test?
While a hemoglobin test is often used to detect anemia, a hemoglobin a1c test is used to diagnose diabetes or monitor your blood sugar (glucose). Glucose in your blood sticks to hemoglobin. The hemoglobin a1c test measures how much glucose has attached to your hemoglobin over time. Higher levels mean higher blood sugar.
A note from Cleveland Clinic
A hemoglobin test is a simple, straightforward procedure that can provide valuable insight into your health. It’s just one piece of the puzzle to understanding how your blood cells are working to keep you healthy. Ask your healthcare provider what your results mean for your care plan if they’re higher or lower than normal.
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