▁or ▁newly ▁produced ▁red ▁cells ▁( ret icul ocy tes ) ▁are ▁larger ▁than ▁the ▁mean ▁( aver age ) ▁size , ▁due ▁to ▁slow ▁shr ink age ▁of ▁normal ▁cells ▁over ▁a ▁normal ▁red ▁cell ▁circul ating ▁lifetime . ▁Thus , ▁chron ic ▁ob struct ive ▁pul mon ary ▁disease ▁( CO PD ), ▁in ▁which ▁red ▁cells ▁are ▁rapidly ▁produced ▁in ▁response ▁to ▁low ▁o xygen ▁levels ▁in ▁the ▁blood , ▁often ▁produces ▁m ild ▁macro cy t osis . ▁Also , ▁rapid ▁blood ▁replacement ▁from ▁the ▁mar row ▁after ▁a ▁tra um atic ▁blood ▁loss , ▁or ▁rapid ▁red ▁blood ▁cell ▁turn over ▁from ▁rapid ▁hem ol ysis ▁( G 6 PD ▁def ic iency ), ▁also ▁often ▁produces ▁m ild ▁macro cy t osis ▁in ▁the ▁associated ▁an emia . ▁ ▁Di agn osis ▁Several ▁tests ▁can ▁help ▁to ▁el uc id ate ▁the ▁underlying ▁cause ▁of ▁a ▁person ' s ▁macro cy t ic ▁an emia . ▁A ▁peri pher al ▁blood ▁sm ear ▁is ▁often ▁recommended ▁as ▁a ▁first ▁step ▁in ▁the ▁evaluation ▁to ▁determine ▁if ▁the ▁macro cy t ic ▁an emia ▁has ▁meg al ob last ic ▁features ▁since ▁the ▁causes ▁of ▁meg al ob last ic ▁and ▁non - m eg al ob last ic ▁macro cy t ic ▁an emia ▁differ ▁and ▁making ▁this ▁distinction ▁can ▁narrow ▁the ▁list ▁of ▁differential ▁diagn oses . ▁▁ ▁For ▁non - m eg al ob last ic ▁macro cy t ic ▁an em ias , ▁a