I'm 43 yo with low libido for a while. blood work shows testosterone @ 314 ng/dl (range is 292-867). doc says is normal. but, since lab range is for *huge* age range i don't get how 314 is ok for 43 yo?

Testosterone : That is toward the low end of the normal range for a man your age. However, the values can vary quite a bit, so i would check 3 separate morning values.

Low testosterone: Male sexual health that's not only depend on testosterone alone. You also have to take into account Estradiol levels, a protein called serum binding globulin, dhea, prolactin level, and free testosterone. You could have low normal levels of testosterone but elevated levels of Estradiol which also can cause the same effect this can lower your sex drive and your inability to have energy. Low it is !