What is the definition or description of: low testosterone?

Lab vs clinical: Laboratory definition of low testosterone is a result below lower limit of normal reference range for that person's age & gender. Blood should be drawn in early morning (before 10am) w/2 abnormal results to support clinical definition of low t (hypogonadism) which may include low energy, loss of or inability to gain muscle, increase in abdominal fat, depression, cognitive impairment, loss of libid.