Hemoglobin Level Test

Hemoglobin May Be Measured Via a Blood Test

Blood tube sitting on blood results with technician at microscope in lab
Hemoglobin levels in the blood can help a physician determine what is causing various physical symptoms. Rafe Swan/Cultura/Getty Images

Hemoglobin is a protein that is contained within red blood cells (RBCs). Hemoglobin is the part of the red blood cell that carries oxygen to, and carbon dioxide away from, the cells in the body. Without the right amount of hemoglobin in the red blood cells, the cells of the body will not be able to receive enough oxygen. When a problem with hemoglobin is suspected, a physician will order a blood test to see if a patient has normal hemoglobin levels.

When hemoglobin is abnormal, the shape of the red blood cells is affected. The distinctive shape of a red blood cell—which looks like a donut that doesn't have a complete hole through the middle—is altered. Having the right shape helps red blood cells to travel through the blood vessels and do their job. A malformed red blood cell may not be able to perform its functions in the body. And a red blood cell of the wrong size or shape may have trouble passing easily through blood vessels. A normal hemoglobin level will vary slightly from person to person, which is why the hemoglobin test result will be used along with other tests to make healthcare decisions.

The Hemoglobin Level Test

The hemoglobin level in blood may be tested during the course of diagnosing or monitoring many diseases and conditions. This test is not specific enough to be used by itself to diagnose any particular condition. This is why, in most cases, physicians will use the results of the hemoglobin level test in along with the results of another blood test, the hematocrit level test.

The hematocrit level is the volume of red blood cells measured in a blood sample. Other test results, as well as a history of signs and symptoms, may also be used to determine what is happening in the blood.

Reference Range For Hemoglobin Level

A hemoglobin test is typically ordered as one part of a complete blood cell (CBC) count.

Hemoglobin levels in the blood are often measured as grams per deciliter of blood, but other measuring units may also be used. The type of units used will depend on what is commonly used by the lab that is processing the blood samples. Each lab will have its own definition of a "normal" hemoglobin range, therefore the levels given below are only examples, and shouldn't necessarily be used to compare with any actual test results. Talk to your physician if you have any questions regarding the levels reported in a hemoglobin test and what they might mean for your health.

 Example Hemoglobin Level Reference Ranges
 Approximate Range for Women 12.1 to 15.1 gm/dl
 Approximate Range for Men 13.8 to 17.2 gm/dl
 Approximate Range for Children 11 to 16 g/dl
 Approximate Range for Pregnant Women 11 to 12 g/dl
 Expressed in grams per deciliter of blood (g/dl)  



Why Do We Measure Hemoglobin?

Hemoglobin levels that are higher than typical may be caused by low oxygen levels. A low level of hemoglobin could be associated with diseases and conditions such as congenital heart diseasecor pulmonale (a complication associated with emphysema), increased red blood cell production caused by an excess of erythropoietin, pulmonary fibrosis (scarring in the lungs), or polycythemia vera (a rare disease of the bone marrow).

A low level of hemoglobin is a common condition called anemia. This is the most common of the blood disorders, and it has many different causes. There are a wide array of diseases and conditions that are associated with anemia, like erythropoietin, hemorrhaging, malnutrition, overhydration, lead poisoning, or deficiencies in iron, folate, vitamin B12 or vitamin B6. 

What If Your Hemoglobin Is Low?

Low hemoglobin and anemia are common, especially in people with chronic illnesses like inflammatory bowel disease (IBD). However, getting the underlying disease under control will help in correcting the problem.

There are other effective treatments that a physician can prescribe to treat anemia.  


Sohrabi F, Stump-Sutliff K. "Hematocrit." University of Rochester Medical Center. 2015. 30 Jun 2015.