People who do not know whether they make sickle hemoglobin (hemoglobin S) or another abnormal hemoglobin (such as C, Î² thalassemia, E) can find out by having their blood tested. This way, they can learn whether they carry a gene (i.e., have the trait) for an abnormal hemoglobin that they could pass on to a child.eople who do not know whether they make sickle hemoglobin (hemoglobin S) or another abnormal hemoglobin (such as C, Î² thalassemia, E) can find out by having their blood tested. This way, they can learn whether they carry a gene (i.e., have the trait) for an abnormal hemoglobin that they could pass on to a child.