Hemoglobin test

A hemoglobin test is a blood test. It measures the amount of a protein in red blood cells called hemoglobin. Hemoglobin carries oxygen to the body's organs and tissues when you breathe in. Then it carries the waste gas carbon dioxide back to the lungs to be breathed out. If a hemoglobin test shows that your hemoglobin level is lower than it should be, that's a sign of a condition called anemia. Causes of anemia include low levels of certain nutrients, blood loss and some long-term diseases.

You may have a hemoglobin test for various reasons, including: To check your overall health. Your healthcare professional may test your hemoglobin as part of a complete blood count (CBC) during a routine checkup. A CBC is done to look at your general health and to screen for a variety of disorders, such as anemia. To find the cause of certain symptoms. A hemoglobin test may be done if you have weakness, fatigue, shortness of breath or dizziness. These symptoms may point to anemia or polycythemia vera. A hemoglobin test may help find these or other medical conditions. To monitor a medical condition. If you have anemia or polycythemia vera, your healthcare professional may use a hemoglobin test to track your condition. The test results also can help guide treatment.

If your blood will be tested only for hemoglobin, you can eat and drink before the test. If your blood also will be tested for other reasons, you may be told not to eat before the test. This is called fasting. It's done for a certain amount of time before your blood sample is taken. Your healthcare team will give you instructions.

For a hemoglobin test, a member of your healthcare team takes a sample of blood. Often, this is done by inserting a needle into a vein in the arm or the top of the hand. For infants, the sample may be taken by pricking the heel or finger. After the test, your healthcare team may have you wait in the office for a few minutes. This is done to make sure that you don't feel dizzy or lightheaded. If you feel fine, you can get back to your usual activities. The blood sample is sent to a lab to be checked.