I suspect this question should read "How long does a red blood 
cell live." A red blood cell lives for between 100 and 120 days. It 
takes 7 days for a new red blood cell to develop from stem cells. Stem 
cells are similar to base cells. They can also be seen as a general 
template from which specialized cells are made. Stem cells can be taken 
from a newborn baby's umbilical chord or extracted from an adult blood 
donor's blood.