IRMS's blog

a blog by Serena H. Chen, M.D., IRMS Reproductive Medicine at Saint Barnabas, January 31, 2012

How do you know what is “normal”? In medicine, “normal” can be defined in many different ways. For many lab values, “normal” is defined by the general population. What values do most people have for this particular lab test? A common criteria is to see what value do 95 percent of people have for this particular lab value? If you are outside the 95th percentile, then your lab value is “abnormal.” But what population do you choose? What if a lot of people in your population are actually abnormal?