Hemoglobin is the protein molecule in red blood cells; it picks up oxygen from the lungs and delivers it to the body's tissue to maintain the good condition of cells. Although hemoglobin functions primarily as an oxygen carrier, it is also important in the transport of carbon dioxide and in the maintenance of the acid-base balance of the body tissues.

Hemoglobin is normally produced by the red blood cells in the bone marrow. It circulates with the cell until it has aged for approximately120 days. When the old cell is filtered from the blood by the spleen, the components of the hemoglobin molecule are either reutilized or excreted. The iron contained in hemoglobin is responsible for the red color of blood.

Hemoglobin Levels: In each milliliter of blood there are approximately 4.5 billion red cells and 150 milligrams of hemoglobin. The normal ranges for hemoglobin depend on the age and sex of the person.

• Newborns hemoglobin level is 17-22 grams/ 100ml of blood
• One month baby is 11-15 grams/ 100ml of blood
• Normal hemoglobin level for men is 14-18 grams/100ml of blood.
• Normal hemoglobin level for women and children is 12-16 grams/100ml of blood.
• Men after middle age is 12-16 grams/ 100ml of blood
• Women after middle age is 11.7-13.8 grams/100ml of blood
• The body cannot tolerate an acute reduction of more than 30% in the hemoglobin content of the body (as in hemorrhage), if this occur the following symptoms such as dizziness and faintness will result. However, a gradual decrease in hemoglobin over a period of weeks, as in pernicious anemia, may be tolerated until the hemoglobin level is 25% of normal.

Low and High Hemoglobin level:

• Low hemoglobin level is referred to as being anemic. Cause of anemia includes loss of blood due to surgery, injury, and internal bleeding, nutritional deficiency, bone marrow problem, and abnormal hemoglobin.
• High hemoglobin level is seen in smokers and in people living in high altitudes areas. Dehydration can also cause high hemoglobin level; it can be corrected as soon as normal proper fluid balance is restored. Other causes include; bone marrow problem and excessive intake of drug erythropoietin (Epogen) by athletes for blood doping purposes.

Fetal Hemoglobin. The blood of newborn infants contains fetal hemoglobin. Fetal hemoglobin has a greater oxygen-carrying capacity at low pH (high acid concentration) than adult hemoglobin. After birth, the infant's red cells produce less fetal hemoglobin and more adult hemoglobin.

Abnormalities. The composition of hemoglobin is the same in all people. Abnormalities of the hemoglobin molecule may be produced by genetic mutations, which alter one or more amino acids in the globin chain; these alterations in the genes are very rare. Since genes are inherited, and they contain the information needed to make a protein, if a mutation produces an abnormal hemoglobin gene in a person, the gene will be passed on to his or her children. The children will produce modified hemoglobin identical to that of the parent. Most mutations in hemoglobin produce no problem, but if these alterations occur at certain critical points, severe illness such as sickle-cell anemia and thalassemia may result. Sickle-cell anemia is a serious disease in which there is a replacement of one amino acid in each beta chain by an incorrect amino acid.