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Defining a clinically relevant lower limit of “normal” blood testosterone level is challenging, in part because levels decline gradually as men age. An additional complication is that laboratories post varying reference ranges for testosterone levels, which is the issue examined in this survey of 120 hospital-associated laboratories in 47 U.S. states.
Mean lower and upper limits for total testosterone reference ranges at surveyed laboratories were 231 ng/dL and 850 ng/dL, respectively. However, lower limits ranged from 160 to 300 ng/dL, and upper limits ranged from 726 to 1130 ng/dL. About one third of hospitals sent specimens to large outside reference laboratories (e.g., Quest, Mayo, ARUP). About one third of hospitals used age-stratified …