Hi Chirley,
As far as I understand NRBCs in adults indicate a condition producing haemopoietic (the fabrication of blood) stress such as severe infection, hypoxia (not enough oxygen) or massive acute bleeding. We know that your HGB is sometimes very low

and that can lead to NRBCs in the blood.
http://www.sysmex.co.za/files/f1/Image/pic_305/NRBC.pdf
Kind regards
Birgitta-A