CLINICS CARE POINTS
*Measure testosterone levels on 2 or more days in early morning hours in a fasting state
*Measure total testosterone concentration using an LC-MS/MS assay, if available, in a laboratory that is certified by an accuracy-based benchmark, such as the CDC HoST Program
*Avoid making a diagnosis of testosterone deficiency based on 1 low value or only on the basis of testosterone levels
*Avoid measuring testosterone levels during an acute illness
*Measure free testosterone level when binding protein abnormality is suspected or when the total testosterone levels are at or near the lower limit of the normal range for men
*Use an equilibrium dialysis method for the measurement of free testosterone level in a reliable laboratory
*Avoid the use of tracer analog methods for free testosterone measurement
*For total testosterone assays that are certified by the CDC HoST Program, the published harmonized references can be applied. The 2.5th, 5th, 95th, and 97.5th percentile values of the harmonized reference range for healthy young, nonobese men, ages 19 years to 40 years, are 264 ng/dL, 303 ng/dL, 852 ng/dL, and 916 ng/dL, respectively
*Lack of standardization of the equilibrium dialysis method has retarded efforts to generate harmonized reference ranges for free testosterone levels. Clinicians have to rely on reference ranges provided by a laboratory. Reference ranges for free testosterone estimated using the ensemble allostery model have been published
