anniekim Red blood count might in indeed go back to normal range, or be low, or high, it depends on a number of factors. My point is this can be calculated. The assumption that it will go back to normal is just a guess.
Let me give an example. Suppose there was a great reduction in blood volume, and RBC count per unit volume went up a little. Total RBC numbers could still be low, its the concentration that is high. So restoring blood volume would, in this case, only result in more plasma, the same number of RBCs would be distributed across the higher volume, and total RBC count would be unaltered. This would mean the diagnosis moved from low blood volume to anemia.
Indeed its possible RBC count goes up only because the blood volume is low, essentially concentrating the RBCs. Its also possible that these high concentrations may inhibit new RBC formation, resulting in low total RBC number even if concentration is high.