Q. In high altitudes is it necessary for the blood to have less or more hemoglobin?
In high altitudes the oxygen concentration and air is rarefied is lower than in low altitudes. In this situation the efficiency of the respiratory system must be greater and thus the organism synthesizes more hemoglobin and more red blood cells trying to get more oxygen this phenomenon is known as compensatory hyperglobulinemia.
The compensatory hyperglobulinemia this is the reason why athletes that will compete in high altitudes need to arrive in the place some days before the event so that there is time for their body to make more red blood cells and they will be less affected by the effects of the low atmospheric oxygen concentration that are fatigue, reduced muscular strength.