What is a hemoglobin test?

hemoglobin test

The hemoglobin test measures the levels of hemoglobin in the blood. Hemoglobin is a protein in red blood cells that carries oxygen from the lungs to the rest of the body. Abnormal levels of hemoglobin could be a sign of a blood disorder.

Other names: Hb, Hgb

For what do you use it?

Hemoglobin analysis is commonly used to detect anemia, an abnormally low level of red blood cells in the body. When a person has anemia, the cells do not receive the oxygen they need. Hemoglobin tests are also commonly done with other tests, for example:
  • Hematocrit, which measures the percentage of red blood cells in the blood
  • Complete blood count, which measures the number and type of blood cells

Why do I need a hemoglobin test?

Your doctor or health professional may ask for this test as part of a routine exam or if you:
  • You have symptoms of anemia such as weakness, dizziness, paleness, or cold hands and feet
  • Have a family history of thalassemia, sickle cell anemia, or other inherited blood disorders
  • Eat a diet low in iron and minerals
  • Have a long-term infection
  • You have lost an excessive amount of blood from a wound or surgical procedure

What happens during a hemoglobin test?

A doctor or health professional takes a blood sample from a vein in one arm using a small needle. After inserting the needle, remove a small amount of blood and place it in a test tube or vial. You may feel mild discomfort when the needle is inserted or removed. This process usually takes less than five minutes.

Will I have to do something to prepare for the test?

No special preparation is necessary for a hemoglobin analysis. If your doctor has ordered other tests with your blood sample, you may be instructed not to eat or drink anything for several hours before the test. Your doctor or health professional will tell you if you should follow any special instructions.

Does this test have any risk?

The risks of a blood test are minimal. After the test, some people feel mild pain, dizziness, or a bruise. Usually, these symptoms disappear quickly.

What do the results mean?

hemoglobin test

Hemoglobin levels may be outside normal limits for many reasons.
If hemoglobin levels are low, this could be a sign of:
  • Different types of anemia
  • Thalassemia
  • Lack of iron
  • Liver disease
  • Cancer and other diseases
If hemoglobin levels are high, this could be a sign of:
  • Lung disease
  • Heart disease
  • Polycythemia vera, a disorder in which the body produces too many red blood cells. It can cause headaches, fatigue, and shortness of breath
If any of your levels are abnormal, that does not necessarily mean you have a medical problem that requires treatment. Diet, activity level, medications, a woman's menstrual cycle, and other considerations can affect the results. Also, you may have an abnormally high level of hemoglobin if you live in a highland region. Ask your doctor or health professional what your results mean.

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

Some forms of anemia are mild, while others can be serious and even life-threatening if left untreated. If you are diagnosed with anemia, be sure to talk to your doctor or health professional to find out what is the best treatment plan for you.