How worried should i be about an abnormal hemoglobin test resul that has to be retested?

Varies: There are in excess of several hundred recorded mutations in the hemoglobin molecules & some are little more than a curiosity and some (sickle cell) could have significant implications.The screening process just selects those who need to be looked at more closely. I would not spend a lot of emotional energy at this point. Get more facts first.