Free Testosterone Increases Libido

Do folks experience increased libido when on testosterone, and if so why?

Yes, sexual function is improved with testosterone replacement. Article over folks, thanks for stopping by.


Let’s dive into it further. Firstly, this is noted many times in studies involving hypogonadal men.

In 6 journal articles that covered trials that reported the effect of testosterone on libido, testosterone therapy was associated with greater improvements in libido but no significant improvements in self-reported erectile function compared with placebo

While I agree with the effect on libido, it’s an odd finding in respect to erectile function due to anecdotes and personal experience of erection quality when on-cycle. This could be due to issues in the studies themselves, with the journal going on to say that there is inconsistency across trials. For example, there’s a lack of a control group during many of these studies, instead using comparisons and self-reporting on before and after treatment. Rather than saying for sure that testosterone has not effect on erection quality, let’s tuck that away for future.

We do know however that testosterone supplementation is associated with an increase in sexual function. In a sample size of 922, free testosterone and libido were correlated. Note on these graphs: the libido score is ranked between 0-14 with 14 being best and 0 being worst. The lines displayed on the top left graph is what is of most interest, with the the curves shifted most to the right representing higher free T and higher libido respectively (actually, it’s bioavailable T, which is free T plus albumin bound, but point still mostly stands).

It’s this high free T that seems to impact libido most. In a sample of 2019 men aged 40-79, with all men in this sample being with normal range. Researchers found that low free testosterone is associated with new and worsening sexual symptoms including desire, and erectile dysfunction.

What is Free Testosterone?

Simply, unattached testosterone. Testosterone attaches to either albumin or SHBG, or remains free (<5% of total test). The former two bind loosely and tightly to testosterone respectively reducing free testosterone, with albumin being a more transient state than testosterone bound to SHBG. Despite it being only a small amount of total testosterone, free test is believed to be the metabolically active fraction.

How Do You Increase Free Testosterone?

Injecting testosterone is one way. Actually, it’s the only way I know to significantly improve free testosterone. In one study, free testosterone had a mean value of 2.05-2.29ng/mL at baseline, which improved 34% even at a relatively low dose of just 100mg test every week.


Exogenous test increases free test, presumably due to the higher testosterone and an unchanged SHBG (at least initially) and albumin leaving a higher amount circulating and unbound. This gives the benefit of increased libido to folks running high levels of test, and probably even to folks on TRT levels, though data is more conflicted on the latter. Of course, for those not running test on cycle and experiencing suppression and lower libido, the reason is due to lower free testosterone. Prevailing wisdom had been to always run test with any cycle, though the introduction of SARMs means more folks running cycles without a test base - as their total test decreases due to suppression, so does free test, causing the reduction in libido.