As for the topic, it seems that the "kick-in" time before test increase libido is longer if T has been low for a while.
(Or maybe it's because of the lower dosages in TRT)
But my feeling is that friends, etc that needed TRT and have went some time with low T, noticing reduced libido, takes some weeks to reverse this, (often a gradual increase over time), while when you are normal or on TRT and dose up with more T, the effect seems much more immediate. As soon as the circulating T is high, libido goes up too
For myself I notice it doesn't take long at all.
It's usually always high though, but I never let T fall very low either.
I've tried some androgens as prosexual/aphrodisiacs (don't ask me why when I didn't need it, but I had a (or have at times) period where I kinda go even further than what I can handle, anyways..
I noticed that halotestin will impact it some within hours, but that it also seemed to have a lag effect of one day.
I wonder if that Is because of 5alpha reduction taking place and needing some time, or it might just be I was just still very amped up the next day.
Test suspension also seems to work right away, but I would also take that both the same day and the day before.
(During those periods I did have sex the day before as well, but more "normal")
Not too sure what those experiences have told me really,
except that this seems to be, at least also, a neurotransmitter like effect,
and not dependent on gene transcription taking place, as it seems to fast for that. But I also think there is a gene regulatory side to it as well.