The serum testosterone can be measured at any time in men who are using any of the transdermal preparations, with the recognition that the peak values occur six to eight hours after application of the nonscrotal patch. The concentrations fluctuate when the gel is used, but not in a predictable way, so at least two measurements should be made at any dose of gel; the time of measurement does not appear to matter.
The timing of the libido return would vary from patient to patient. You may want to consider rechecking the testosterone level while on the Androgel to ensure they have normalized.
If there continues to be a dearth of libido despite a normal testosterone level, you may want to consider looking for another cause other than a low testosterone level.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Thanks,
Kevin, M.D.
Bibliography:
Snyder. Testosterone treatment of male hypogonadism. UptoDate, 2004.