Normal, High, and Low Hemoglobin Levels

Low Hemoglobin Levels can lead to serious condtions such like Heart Attacks and Congestive Heart Failure. In this article you are going to learn about the causes of Low Hemoglobin Levels, the Normal Hemoglobin Levels based on age and gender, and the Causes of High Hemoglobin Levels. Hemoglobin Normal Level is very close to Normal Hematocrit Levels. also alternations to Hemoglobin Level would usually lead to High and Low Hematocrit Levels. Hemoglobin Levels are used with RBC Count and Hematicorit Levels to calculate the Mean Corpuscular Hemoglobin (MCH) and Mean Corpuscular Hemoglobin Concentration (MCHC) respectively. Both MCH and MCHC are Red Blood Cell Indices which are used to classify Anemia.


Hemoglobin (Hgb) is found in Red Blood Cells (RBCs) as well as other types of cells. In Red Blood Cells Hemoglobin is functioning as a carrier for the inhaled Oxygen molecules (O2) from the lungs to the tissues of other body organs. The Oxygen in generating energy in the body organs by burning the food, as a result, unwanted Carbon Dioxide molecules (CO2) are produced and carried to the lungs to be exhaled.

Hemoglobin consists of Heme and Globin. Heme is a chemical compound of an Iron ion that is surrounded by porphyrin. The Iron ion in Heme is responsible of binding with the Oxygen molecules while Globin is a protein that binds with the Carbon Dioxide molecules.


Hemoglobin levels reflect the Hgb concentration and are measured in terms of grams per deciliter (g/dl). The levels are very close to both Hematocrit (Hct) levels and Red Blood Cell (RBC) Count. Hemoglobin, Hematocrit, and Red Blood Cell count tests are ordered together by a physician in order to give a clear picture of the cause of abnormality with any of the tests.As an example, with a normal RBC size, Hematocrit level percentage should approximately equals 3 times the Hemoglobin levels in terms of g/dl. If 3 times ratio alternates, this would be an indication of abnormalities with the Red Blood Cells size.




Hemoglobin Levels
  Normal Hemoglobin Levels
    Normal Alternations to Hemoglobin Levels
  Causes of Low Hemoglobin Levels
  Causes of High Hemoglobin Levels
Hemoglobin Variants
  Benefits of having different Hemoglobin Variants
  Genetics and structure of Hemoglobin Variants
Normal Hemoglobin Variants
  Embryonic Hemoglobin
    Hemoglobin Gower 1
    Hemoglobin Gower 2
    Hemoglobin Portland 1
    Hemoglobin Portland 2
Fetal Hemoglobin (Hemoglobin F)
  Hemoglobin F Normal Levels
  Function of Hemoglobin F
Adult Hemoglobin (Hemoglobin A)
  Hemoglobin A1
Hemoglobin A2





Normal Hemoglobin Levels

Normal Hemoglobin levels vary based on age and gender. Children normally have the highest Hemoglobin levels and Hemoglobin concentration tends to decrease with age. Males also tend to have higher Hemoglobin concentration than females. Pregnancy also decreases the Hemoglobin level for females.


The following listing shows the normal Hemoglobin ranges for each distinct age or sex group:

Normal, High and Low Hemoglobin Levels

Normal, High and Low Hemoglobin Levels

Newborn: the Normal Hemoglobin Level ranges between 14 and 24 g/dl.

Newborn to 2 weeks: Hemoglobin Normal Ranges between 12 and 20 g/dl.

2 to 6 months: Normal Hemoglobin Level Range is 10 to 17 g/dl.

6 to 12 months: Normal Hemoglobin Level ranges between 9.5 and 14 g/dl.

1 to 6 years: 9.5 to 14 g/dl.

6 to 18 years: 10 to 15.5 g/dl.

Adults over 15: The values may be decreased slightly.

Male: 14 to 18 g/dl.

Female: 12 to 16 g/dl.

Pregnant Female: More than 11 g/dl.



Normal alternations to Hgb levels

As with the case of pregnant females, Hemoglobin Levels may increase or decrease due to normal causes that don’t indicate or associate with any disorders. The following is a listing of the normal reasons that can cause alternations to the Hemoglobin levels, these causes should be considered before jumping into any conclusions that the Hemoglobin levels are alternated due to a disorder:


  • Hemoglobin levels vary during the day within the same person. Hgb levels are always higher during the morning and lower at evening. The highest level can be seen around 8 am and the lowest level can be reached around 8 pm. The difference between the highest and lowest levels during the day can be a slight difference but it can reach as much as 1 gram per deciliter.
  • Hemoglobin concentration is normally affected by hydration. Hydration increases the plasma level in the blood, and as a result Red Blood Cells, Hematocrit, and Hemoglobin levels will be decreased due to overhydration or increased due to dehydration. Even though the Hemoglobin level can be affected by hydration, the patient is not required to be fasting when the Hgb test is done.
  • Heavy smokers normally have higher Hemoglobin levels than nonsmokers. The cause of those high hemoglobin levels among heavy smokers is not related to any disorder but it is a normal response to the little oxygen they inhale. Heavy smokers inhale large amounts of smoke and very few amounts of oxygen due to that death causing habit, as a result, the tissues in the body organs don’t receive enough oxygen to burn the food, release energy and perform their basic vital processes and the human body will produce more than usual Red Blood Cells as an attempt to increase the oxygen supply to the tissues and overcome the possibility that Hemoglobin molecules are not able to bind with enough amount of oxygen molecules. The increased RBC count will lead to high Hgb level.
  • People who live on high elevation normally have high Red Blood Cells count and high Hemoglobin Levels due to the decreased amounts of oxygen in the air at high altitudes. This is also a normal response by the human body in attempt to increase the oxygen supply to the different body tissues by overcoming the possibility that Hemoglobin molecules are not able to bind with enough amount of oxygen molecules and that the increased production of Red Blood Cells would insure a higher supply of oxygen to the body organs and tissues.




Causes of Low Hemoglobin Levels

To assure sufficient oxygen carrying capacity; with very Low Hemoglobin Level the heart have to push more amounts of blood to the different body organs, which puts a strain on the Cardiopulmonary system. Very Low Hemoglobin Levels put the patient at a great risk or Heart Attacks, Congestive Heart Failure, Angina, and Strokes. To avoid such cases from occurring, the causes of Low Hemoglobin levels should be known and treated or controlled if possible.


Low Hemoglobin levels can be a result of using drugs such like Aspirin, Antibiotics, Antineoplastic drugs, Indomethacin, Rifampin, and Sulfonamides.

Low Hemoglobin Levels can be a sign of and caused by any of the following:


–          Anemia is the decrease in Red Blood Cells count which leads to Low Hemoglobin Levels. Anemia is associated with several types of diseases.

–          Hemoglobinopathy is the decrease in Hgb Levels due to a Hemoglobin disorder or any other blood disorders that decreases the RBC count or reduces the life span of Red Blood Cells which cause Low Hemoglobin Levels.

–          Dietary Deficiency with deficiencies of vitamins (B12 as an example) or minerals (Iron) that necessary to produce Red Blood Cells. Also problems with digesting or absorbing those necessary vitamins and minerals will cause producing fewer or small size RBCs and causing the Low Hemoglobin Levels.

–          Pregnancy cause several physiological changes including a chronic state of overhydration which cause the total blood volume to increase and lower down the Red Blood Cells concentration in the blood which is also represented as a Low Hemoglobin Level.

–          Bone Marrow Failure causes lower production of blood cells in general including the Red Blood Cells which leads to low RBC count and Low Hemoglobin Levels.

–          Cancers that cause increased production of other types of blood cells also reduce the production of Red Blood Cells and cause Low Hemoglobin Levels. These cancers include:

  •  Lymphoma a cancer which occurs as a result of increased production of B or T Lymphocyte White Blood Cells.
  • Hodgkin’s Lymphoma a cancer which occurs as a result of increased production of Lymphocytes.
  • Leukemia a cancer which occurs as a result of increased production immature white blood cells.
  • Multiple Myeloma a cancer which occurs as a result of increased production of Myeloma cells which are a malignant plasma cells that accumulate in the bone marrow and reduces the production of blood cells.

–          Rheumatoid Vascular Diseases such like Rheumatoid Arthritis and Lupus are associated with reduced production of Red Blood Cells which cause low RBC count and also Low Hemoglobin Levels.

–          Hemolytic Anemia is the disease that occurs when abnormal breakdown of Red Blood Cells causes a shorter life span for the RBCs. The RBCs breakdown reduces RBC count, and therefor causes Low Hemoglobin Levels.

–          Renal Disease cause the kidneys to secrete fewer amounts of the Erythropoietin hormone which is responsible in stimulating the production of Red Blood Cells, as a result fewer RBCs are produced causing low hemoglobin levels.

–          Cirrhosis is the state of fluid retention and overload that is caused by chronic liver disease. The fluid overload cause the Red Blood Cells to be diluted and make up a low percentage of the total blood volume and low hemoglobin levels as a result.

–          Prosthetic Heart Valves cause the a mechanical trauma to the Red Blood Cells which reduces the RBCs life span and as a result the RBC count will be reduced causing Low Hemoglobin Levels.




Causes of High Hemoglobin Levels

If Hemoglobin Levels are too high as a result of high Red Blood Cells count, intravascular sludging can occur which leads to stroke. To avoid such a case from happening, the causes of High Hemoglobin levels should be figured and treated.


High Hemoglobin levels can be a result of using drugs such like Gentamicin and Methyldopa.

High Hemoglobin Levels can be a sign of and caused by any of the following:


–          Erythrocytosis, which is the increase in Red Blood Cells count that is not caused by hematogenic systemic disorder. An example of Erythocytosis the RBC count increases due to physiological response to external stimulations such like living in high altitude.

–          Severe Dehydration decreases the volume of plasma, and as a result, it decreases the total blood volume. Even that Severe Dehydration doesn’t increase or even affect the Red Blood Cells count, however, the consequent reduction of the total blood volume would increase the concentration of RBCs and Hemoglobin in the blood causing high Hgb levels.

–          Polycythemia Vera is myeloproliferative blood disorder which occurs when the bone marrow produces unnecessary massive numbers of Red Blood Cells which leads to High Hemoglobin Level.

–          Cyanotic Heart Defects are a group of Congenital (Birth) Heart Defects that cause the blood which passes the lungs and entering the systemic circulation to reach the other organs to be deoxygenated causing the patient skin to have a bluish or cyan color (be Cyanotic). The human body produces large numbers of Red Blood Cells as physiological response to decreased levels oxygen potential pressure (pO2) resulting from Cyanotic Heart Defects. The High RBC count in the blood will also cause High Hemoglobin Levels.

–          Chronic obstructive pulmonary disease (COPD) cause the airways of respiratory system to be narrowed overtime and leading to insufficient oxygen supplies to the different body members. In advanced cases of the disease, as a result the body produced more Red Blood Cells causing high Hgb Levels.