Blood test

Normal hemoglobin level in the blood

Blood test
Normal hemoglobin level in the blood
Last update: 09/12/2020

What is the normal level of hemoglobin in the blood?

Adult men: 13 - 18 g/dl
Adult women: 12 - 16 g/dl
Boys from 15 years old: 13 - 17 g/dl
Girls from 15 years old: 12 - 15 g/dl
Children from 12 to 14 years old: 12 - 15.5 g/dl
Children from 5 to 12 years old: 11.5 - 14.5 g/dl
Children from 6 months old to 11 years old: 11 - 14.5 g/dl
Babies from 2 weeks old to 6 months old: 9 - 15 g/dl
Newborns: 13 - 20 g/dl

In the International System of Units (SI), hemoglobin in the blood is measured in mmol/L. The normal hemoglobin level in the blood in the SI is:

Adult men: 8 - 11 mmol/l
Adult women: 7.5 - 10 mmol/l
Boys from 15 years old: 8 - 10.5 mmol/l
Girls from 15 years old: 7.5 - 9.3 mmol/l
Children from 12 to 14 years old: 7.5 - 9.6 mmol/l l
Children from 5 to 12 years old: 7 - 9 mmol/l
Children from 6 months old to 11 years old: 6.8 - 9 mmol/l
Babies from 2 weeks old to 6 months old: 5.6 - 9.3 mmol/l
Newborns: 8 - 12.5 mmol/l

Why normal levels can differ across different labs?

Each laboratory must establish its own normal ranges for hemoglobin level in the blood. These ranges depend on the makeup of the local population, the technologies used and the accuracy of the measurement. There may be also slight differences in the normal levels, according to age, gender, race or ethnic origin, geographic region, diet, type of sample and other relevant status.

Your doctor will study the results along with your medical record, screenings, physical condition, symptoms and any other relevant information about your situation.

There are some circumstances that can alter the previous ranges:

  • Black people have slightly lower values of hemoglobin in the blood. They may have a 2% reduction from the normal ranges.
  • Pregnant women have a hemoglobin concentration less than normal to accommodate the increasing maternal blood volume. The normal range for a pregnant woman is from 11 to 12 mg/dl.
  • Hemoglobin show diurnal variation. The hemoglobin values are highest in the morning and lowest in the evening.

What is the role of hemoglobin in the body?

Hemoglobin (Hb) is the main constituent of the RBCs (Red Blood Cell).

Hemoglobin carries out the important function of transportation of oxygen from the lungs to body’s cell through the bloodstream. To a lesser extent, it transports back carbon dioxide from the body to the lungs to be exhaled in the respiratory process.

When fully saturated, each gram of hemoglobin holds approximately 1.34 ml of oxygen per 100 ml of blood.

Hemoglobin is composed of a pigment (heme), which contains iron atoms and the red pigment porphyrin that gives RBC its characteristic red color. In addition, there are other essential elements of an adequate hemoglobin production such as vitamin B12 or folic acid.

What is the hemoglobin blood test used for?

The hemoglobin level is used mainly to screen for anemia, where the hemoglobin level is below the normal range. It is a way to determine the severity of the anemia or the response to a treatment for it.

When hemoglobin level is below the normal range, the cells do not receive enough energy and you can feel fatigue or pale skin.

Anemia is a group of disorders that can be due to multiple causes. The main causes are:

  • Deficiency of some elements: iron-deficiency anemia is due to lack of iron; megaloblastic anemia is due to lack of vitamin B12 or folic acid.
  • Chronic diseases: kidney disorders (renal failure) or liver disorders (cirrhosis, hepatitis, etc.)
  • Post hemorrhagic anemia: due to acute blood loss.
  • Genetic disease: Some genetic disorders may cause an alteration in the hemoglobin production. They are called hemolytic anemias (thalassemia, sickle cell disease, hereditary spherocytosis, etc.)
  • The bone marrow fails to produce enough blood cells: In this group, it can be found the aplastic anemia and the myelodysplastic syndromes.

A low hemoglobin value in the blood requires a further study to know the concrete type of anemia that may be suffering. For this matter, it is useful to study the rest of RBC parameters such as the hematocrit, MCV (Mean Corpuscular Volume), MCH (Mean Corpuscular Hemoglobin), MCHC (Mean Corpuscular Hemoglobin Concentration) and RDW (red cell distribution width).

A high value of hemoglobin, above the normal range, is also clinically significant and it may be due to multiple causes, although the main ones are dehydration and polycythemia vera (a genetic disease where the bone marrow produces too many blood cells).

Where can I find more information about hemoglobin level in the blood?

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Which values are considered a normal hemoglobin level in the blood?

The following values are considered to be normal values:

IMPORTANT: These levels are expressed in gr/dl. They are an example of a healthy woman of about 45 years old with no known disease and not taking any medication. The ranges can be different depending on the laboratory or on your personal circumstances.

12 g/dl12.1 g/dl12.2 g/dl12.3 g/dl12.4 g/dl12.5 g/dl12.6 g/dl12.7 g/dl
12.8 g/dl12.9 g/dl13 g/dl13.1 g/dl13.2 g/dl13.3 g/dl13.4 g/dl13.5 g/dl
13.6 g/dl13.7 g/dl13.8 g/dl13.9 g/dl14 g/dl14.1 g/dl14.2 g/dl14.3 g/dl
14.4 g/dl14.5 g/dl14.6 g/dl14.7 g/dl14.8 g/dl14.9 g/dl15 g/dl15.1 g/dl
15.2 g/dl15.3 g/dl15.4 g/dl15.5 g/dl15.6 g/dl15.7 g/dl15.8 g/dl15.9 g/dl
16 g/dl       
Medically reviewed by our Medical staff on 09/12/2020


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