High hemoglobin levels should be taken seriously. It normally happens when the body needs more oxygen-carrying capability, which happens when you smoke or live at a high elevation area, your RBC production naturally increases to compensate for the lower oxygen supply.
A high hemoglobin can result in blood clots, heart attacks, and strokes. It could also be an indication of another problem, such as lung or heart disease. It is a dangerous long-term condition that can be fatal if not treated.