The Full form of HB is Hemoglobin. HB is the protein molecule in red blood cells that carries oxygen from the lungs to the body’s tissues and returns carbon dioxide from the tissues back to the lungs. Hemoglobin is made up of four protein molecules called globulin chains that are connected together. The normal adult Hemoglobin (abbreviated Hb or Hgb) molecule contains two alpha-globulin chains and two beta-globulin chains. In fetuses and infants, beta chains are not common and the hemoglobin molecule is made up of two alpha chains and two gamma chains. HB is usually measured as a part of the routine CBC (Complete Blood Count) test from a blood sample. Several methods exist for measuring HB, most of which are done currently by automated machines designed to perform different tests on blood. The HB level is expressed as the amount of Hemoglobin in grams (gm) per deciliter (dL) of whole blood, a deciliter being 100 milliliters. The normal ranges for HB depend on the age, beginning in adolescence and the gender of the person. The normal ranges of Hemoglobin in children are from 11 to 13 gm/dL, in adult males it is 14 to 18 gm/dL, in adult women it is from 12 to 16 gm/dL and so on.