Does Finasteride Lower Testosterone?

Article Summary

Finasteride’s reputation for affecting hormones has led many to assume it suppresses testosterone, but the biology is far more nuanced. In this article, we unpack what happens to testosterone when DHT is inhibited, why levels often rise instead of fall, and how this squares with the sexual side effects reported by some users. By separating hormonal myths from clinical evidence, we clarify what finasteride changes, what it doesn’t, and what that means for treatment decisions.

Full Article

Finasteride is a prescription medication originally created to treat benign prostate hyperplasia (BPH), and now commonly used to treat androgenic alopecia (AGA). It achieves this through targeting 5α‑reductase (5AR), an enzyme that converts testosterone to dihydrotestosterone (DHT), lowering levels of DHT in the scalp. DHT is the key androgen driving follicular miniaturization and is known to drive hair loss. Therefore, the finasteride-induced reduction of DHT results in increased hair growth.^[1]Asfour L, Cranwell W, Sinclair R, (2023), Male Androgenetic Alopecia. In: Feingold KR, Adler RA, Ahmed SF, et al., editors, Endotext [Internet], South Dartmouth (MA): MDText.com, Inc.; Available at: … Continue reading 

Despite the high amount of evidence supporting finasteride use, users may be disincentivized due to its potential side effects, including a loss of libido and erectile dysfunction. In some cases, the symptoms can persist after ceasing finasteride use, a condition known as post-finasteride syndrome.^[2]Diviccaro, S., Melcangi, R.C., Giatti, S. (2019). Post-finasteride syndrome: an emerging clinical problem. Neurobiology of Stress. 12. 100209. Available at: https://doi.org/10.1016/j.ynstr.2019.100209

The potential for the finasteride mechanism to lower testosterone levels is a common fear; however, the sexual side effects observed in a minority of finasteride users do not occur due to a finasteride-induced reduction in testosterone. Paradoxically, finasteride causes a rise in testosterone, yet occasional sexual side effects are still seen.

In this article, we will discuss whether finasteride lowers testosterone and what the mechanisms are behind sexual side effects in finasteride users.

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How Does Finasteride Work?

AGA is a progressive remodelling of the hair follicle, which is induced by androgen sensitivity. Activation of the androgen receptor shortens the growth phase of the hair growth cycle, resulting in progressive miniaturization of susceptible hair follicles. The rest phase of the hair growth cycle remains the same or lengthens, altering the ratio of growth to rest from 12:1 to 5:1. As a result of follicle miniaturization, the hair growth is insufficient to penetrate the outer layer of the skin.^[3]Ho, C.H., Sood, T., Zito, P.M., (2024), Androgenetic Alopecia. Available at: https://www.ncbi.nlm.nih.gov/books/NBK430924/ (Accessed: 07 January 2026)

DHT is the key androgen driving follicular miniaturization. As mentioned above, the 5AR enzyme metabolizes testosterone to produce DHT. Both 5AR and DHT have been shown to be elevated in balding areas of the scalp compared to the hair-containing scalp.^[4]Dallob, A.L., Sadick, N.S., Unger, W., Lipert, S., Geissler, L.A., Gregoire, S.L., Nguyen, H.H., Moore, E.C. and Tanaka, W.K. (1994). The Effect of Finasteride, a 5 Alpha-Reductase Inhibitor, on … Continue reading

Effect of Finasteride on DHT Suppression

Finasteride suppression of DHT can be fit to a non-linear (logarithmic) dose-response curve, i.e., even very low levels of finasteride (≥0.2 mg/day) can produce near-maximal suppression of DHT in both the serum and the scalp.^[5]Drake, L., Hordinsky, M., Fiedler, V., Swinehart, J., Unger, W.P., Cotterill, P.C., Thiboutot, D.M., Lowe, N., Jacobson, C., Whiting, D., Stieglitz, S., Kraus, S.J., Griffin, E.I., Weiss, D., … Continue reading The majority of its inhibitory action is achieved at low doses, with higher dosing only providing marginal additional effects.

Clinical trials have demonstrated that finasteride treatment decreases levels of DHT in the serum by 71-72% and in the scalp by 64-69%.^[6]Drake, L., Hordinsky, M., Fiedler, V., Swinehart, J., Unger, W.P., Cotterill, P.C., Thiboutot, D.M., Lowe, N., Jacobson, C., Whiting, D., Stieglitz, S., Kraus, S.J., Griffin, E.I., Weiss, D., … Continue reading

Clinical Effectiveness

The clinical effectiveness of finasteride in improving hair growth has been demonstrated in multiple clinical trials. It has been shown to improve hair growth and slow further hair loss across 1-year, 2-year, and 5-year clinical trials, with 65% of finasteride-treated men demonstrating increased hair count at 5 years compared to 0% of the placebo-treated (sugar pill group) men.^[7]Finasteride Male Pattern Hair Loss Study Group. (2002). Long-Term (5-Year) Multinational Experience With Finasteride 1 mg in the Treatment of Men With Androgenetic Alopecia. Eur J Dermatol. 12:38-49. … Continue reading,^[8]Shapiro, J., Kaufman, K.D. (2003). Use of Finasteride in the Treatment of Men With Androgenetic Alopecia (Male Pattern Hair Loss). J Investig Dermatol Symp Proc. 8(1):20-23. Available at: … Continue reading

Does Finasteride Lower Testosterone?

Myths around finasteride treatment resulting in testosterone deficiency abound; however, there is no evidence supporting this. In fact, research has actually shown that finasteride treatment increases levels of testosterone.

A four-year clinical trial investigating the safety and efficacy of finasteride in patients with BPH demonstrated a ~15% rise in testosterone in the serum compared to the placebo group.^[9]Roehrborn, C., Lee, M., Meehan, A., Waldstreicher, J. (2003). Effects Of Finasteride On Serum Testosterone And Body Mass Index In Men With Benign Prostatic Hyperplasia. Urology. 62(5). 894–899. … Continue reading Additional trials have also reported a moderate rise in testosterone (5-33%; not dose-dependent).^[10]Drake, L., Hordinsky, M., Fiedler, V., Swinehart, J., Unger, W.P., Cotterill, P.C., Thiboutot, D.M., Lowe, N., Jacobson, C., Whiting, D., Stieglitz, S., Kraus, S.J., Griffin, E.I., Weiss, D., … Continue reading,^[11]Uygur, M.C., Arık, A.İ., Altuğ, U., Erol, D., (1998). Effects Of The 5α-Reductase Inhibitor Finasteride On Serum Levels Of Gonadal, Adrenal, And Hypophyseal Hormones And Its Clinical … Continue reading,^[12]Amory, J.K., Wang, C., Swerdloff, R.S., Anawalt, B.D., Matsumoto, A.M., Bremner, W.J., Walker, S.E., Haberer, L.J. and Clark, R.V. (2007). The Effect Of 5α-Reductase Inhibition With Dutasteride And … Continue reading

Although the rise in testosterone was significantly different between finasteride- and placebo-treated individuals, levels of testosterone consistently remained within the normal physiological range. The increase in testosterone was identified in women as well as men, and was found to be more pronounced in men with low baseline testosterone.^[13]Albasher, G., Bin-Jumah, M., Alfarraj, S., Al-Otibi, F., Al-Sultan, N.K., Alarifi, S., Alkahtani, S. and Al-Qahtani, W.S. (2020). Prolonged Use Of Finasteride-Induced Gonadal Sex Steroids … Continue reading,^[14]Roehrborn, C., Lee, M., Meehan, A., Waldstreicher, J. (2003). Effects Of Finasteride On Serum Testosterone And Body Mass Index In Men With Benign Prostatic Hyperplasia. Urology. 62(5). 894–899. … Continue reading However, not all patients tested experienced this rise in testosterone.

The evidence therefore supports a short-term rise in testosterone on finasteride treatment, while remaining within the physiological range. Many of these studies were carried out in relation to BPH, where the finasteride doses are higher (generally 5 mg vs 1 mg), so the impact of finasteride for AGA treatment is likely to be even lower.

Why Does Testosterone Increase When DHT Falls?

The inhibition of the 5AR enzyme results in the blocking of the DHT production pathway, resulting in the testosterone that would otherwise have been converted to DHT remaining as testosterone. No large increases in testosterone are seen, as not only do negative feedback adjustments occur, but free testosterone is also thought to be redistributed within the androgen pathway, where it is converted into estradiol. 

Can the Rise in Testosterone Have Sexual Side Effects?

The moderate rise in testosterone identified in individuals taking finasteride does not result in a rise above the physiological range, making sexual side effects directly as a result of the rise in testosterone unlikely. In general, a moderate rise in testosterone levels improves sexual function. This appears to contradict the well-characterized (though uncommon) sexual side effects of finasteride treatment. Therefore, another mechanism must be at work to induce these sexual side effects.

Finasteride Sexual Side Effects

What are the Sexual Side Effects of Finasteride?

Sexual side effects have been reported in a small minority of users. These include:

• Erectile dysfunction
• Ejaculatory dysfunction
• Loss of libido

While these symptoms often improve or resolve on their own, persistent sexual dysfunction has been reported in a very small number of finasteride users, in a condition known as post-finasteride syndrome.^[15]Hirshburg, J.M., Kelsey, P.A., Therrien, C.A., Gavino, A.C. and Reichenberg, J.S. (2016). Adverse Effects And Safety Of 5-Alpha Reductase Inhibitors (Finasteride, Dutasteride): A Systematic Review. … Continue reading However, reports of this condition are controversial, and conflicting results are seen in different studies. If you are interested in learning more, see our article exploring whether post-finasteride syndrome is real.

What is the Prevalence of Sexual Side Effects?

In controlled clinical trials, sexual side effects of taking finasteride are uncommon, but exact estimates vary depending on the dose, study design, and population receiving treatment.

• In a 4-year, randomized, placebo-controlled clinical trial assessing the prevalence of sexual adverse experiences (AEs) on the treatment of BPH with 5 mg of finasteride, 15% of finasteride-treated and 7% of placebo-treated men had sexual AEs within the first year, indicating an increase in AEs in the finasteride group. However, no differences between placebo- and finasteride-treated AEs were seen in years 2-4.^[16]Wessells, H., Roy, J., Bannow, J., Grayhack, J., Matsumoto, A.M., Tenover, L., Herlihy, R., Fitch, W., Labasky, R., Auerbach, S., Parra, R., Rajfer, J., Culbertson, J., Lee, M., Bach, M.A. and … Continue reading
• A meta-analysis (a study where data from multiple independent studies are analyzed) of 15 clinical trials where AGA was treated with 1 mg of finasteride found that only 5.31% of users had adverse sexual effects compared to 3.05% of those taking a placebo.^[17]Lee, S., Lee, Y.B., Choe, S.J. and Lee, W. (2019). Adverse Sexual Effects Of Treatment With Finasteride Or Dutasteride For Male Androgenetic Alopecia: A Systematic Review And Meta-Analysis. Acta … Continue reading
• A different meta-analysis of 17 clinical trials found that men taking finasteride had a 1.29 times higher risk of underactive sexual desire or a 1.47 times higher risk of erectile dysfunction.^[18]Corona, G., Tirabassi, G., Santi, D., Maseroli, E., Gacci, M., Dicuio, M., Sforza, A., Mannucci, E. and Maggi, M. (2017). Sexual Dysfunction In Subjects Treated With Inhibitors Of 5α-Reductase For … Continue reading

Meta-analyses and studies with a high number of participants are the gold standard for assessing the risk of sexual side effects. Smaller studies have put the incidence of sexual side effects higher; however, these results should be interpreted with caution due to the limitations of the clinical trials.

Further caution should be taken due to the “nocebo” phenomenon, where a patient may experience negative symptoms or worse outcomes due to their being informed that the product may cause them harm. 

A small study investigating this phenomenon in patients treated for BPH with 5 mg finasteride found that the group who received counseling on the sexual side effects (i.e., were informed of these side effects) demonstrated a significantly higher proportion of sexual side effects than the group who did not receive counseling (43.6% vs. 15.3%).^[19]Mondaini, N., Gontero, P., Giubilei, G., Lombardi, G., Cai, T., Gavazzi, A. and Bartoletti, R. (2007). Finasteride 5 mg And Sexual Side Effects: How Many Of These Are Related To A Nocebo Phenomenon? … Continue reading

Care should also be taken when interpreting information on natural health websites and online forums, as the perceived prevalence of sexual side effects may seem incredibly high on these. This may occur due to multiple reasons, including:

• Fearmongering due to the desire to sell natural remedies claiming to be sexual side-effect-free (which often isn’t true).
• Users are more likely to post in anger about issues with the product, whereas those content with the product are less likely to post (the “Yelp Effect”).

Why do Sexual Side Effects Occur Despite Higher Testosterone?

As discussed above, increased testosterone (within the physiological range) enhances sexual function. However, despite the slightly raised testosterone seen in men taking finasteride, sexual side effects still occur. Below are three main pathways through which these side effects have been suggested to occur. Please consider that none of these mechanisms have been conclusively proven, and are only suggestions as to how sexual side effects may be occurring.

DHT Depletion

DHT is a potent androgen, binding the androgen receptor with greater strength than testosterone. DHT and testosterone can bind to androgen receptors in the corpora cavernosa (erectile tissue in the penis), causing an upregulation in nitric oxide production and resulting in increased blood flow into the penis and an erection.

It has been suggested that susceptible individuals experiencing decreased levels of DHT on finasteride treatment experience a reduction in nitric oxide production, limiting blood flow into the penis, and, consequently, in erectile dysfunction.^[20]Clapauch, R. (2011). Finasteride and Erectile Dysfunction: Fact or Fiction? Brasília Medical (Medical Experience). 48(4), pp.422–427. Available at: … Continue reading,^[21]Erdemir, F., Harbin, A. and Hellstrom, W.J.G. (2008). 5-Alpha Reductase Inhibitors And Erectile Dysfunction: The Connection. The Journal Of Sexual Medicine. 5(12), pp.2917–2924. Available at: … Continue reading

DHT is also an important contributor to secretory function and semen volume, as controlled by two glands – the prostate and seminal vesicles. These glands are androgen-dependent. DHT is the primary androgen involved, but testosterone can compensate for reduced DHT.^[22]Anitha, B., Inamadar, A.C., Ragunatha, S. (2009). Finasteride-Its Impact on Sexual Function and Prostate Cancer. J Cutan Aesthet Surg. 2(1):12–16. Available at: … Continue reading,^[23]Cai, L.Q., Fratianni, C.M., Gautier, T., Imperato-McGinley, J. (1994). Dihydrotestosterone Regulation of Semen in Male Pseudohermaphrodites with 5 Alpha-Reductase-2 Deficiency. Journal of Clinical … Continue reading

Finasteride treatment does not cause low semen or ejaculatory volume in all users, but this does appear in rare cases. This ejaculatory dysfunction could occur as a result of testosterone not sufficiently compensating for DHT’s role in secretory function.

Neurosteroids in the Central Nervous System

In addition to its ability to convert testosterone to DHT, 5AR is also important in the conversion of other molecules into neurosteroids. Neurosteroids are steroids synthesized within the central nervous system (CNS; formed of the brain and spinal cord) that play a key role in controlling activity within the CNS, including anxiety, stress, and depression. 

Treatment with 5AR inhibitors, such as finasteride, can cause a decrease in active neurosteroids within the CNS and altered transmission of certain signals within the brain. This disrupted neurosteroid signaling has been suggested as a potential cause of the decreased libido side effect that is occasionally seen in users of finasteride.^[24]Irwig, M.S. (2014), Persistent Sexual and Nonsexual Adverse Effects of Finasteride in Younger Men. Sex Med Rev. 2(1):24–35. Available at: https://doi.org/10.1002/smrj.19,^[25]Traish, A.M., Hassani, J., Guay, A.T., Zitzmann, M., Hansen, M.L. (2011). Adverse Side Effects of 5 Alpha-Reductase Inhibitors Therapy: Persistent Diminished Libido and Erectile Dysfunction and … Continue reading

Androgen Redistribution

As discussed above, the inhibition of 5AR results in less testosterone being converted into DHT and a mild rise in testosterone. It has been suggested that the increase in free testosterone may be compensated for through androgen redistribution via conversion to estradiol (an estrogen).

Estradiol levels show a minor rise in finasteride users of approximately 15% (while remaining within physiological reference ranges).^[26]U.S. Food and Drug Administration, (2022), Propecia (Finasteride) Tablets Label. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2022/020788s030lbl.pdf (Accessed: 07 January 2026) For those with a genetic predisposition to high estrogen or whose diets, lifestyles, and environments have elevated their estrogen levels, a finasteride-induced further rise in estrogen may be sufficient for the development of gynecomastia (the development of male breast tissue).

How Can We Reduce the Risk of Sexual Side Effects?

The first step if side effects occur is to speak to your primary care physician to ensure that side effects are recorded and appropriate management steps are taken. If side effects are severe or rapidly worsening, you should immediately see your physician. The strategies discussed below are only applicable if mild to moderate side effects are experienced, and should only be carried out under clinical supervision. More information on finasteride-associated side effects can be found in our articles on topical finasteride and reducing side effects.

• Lowering your daily dose of finasteride

Finasteride produces the majority of its DHT-lowering effects at relatively low doses. The standard finasteride daily dose is 1 mg. Due to its non-linear dose-response curve, lower doses can still have significant effects on lowering serum and scalp DHT and enhancing hair growth.

Finasteride side effects are often dose-sensitive, meaning that lowering the daily dose could be a first step to reducing side effects, without a significant loss in benefits.

• Lowering the frequency of dosing

Mild flexibility in finasteride dosing also allows for carefully controlled alterations in dosing frequency. Finasteride has a relatively short half-life (time taken for the amount of drug in the body to halve), but does accumulate with repeated doses.^[27]Steiner, J.F. (1996). Clinical Pharmacokinetics and Pharmacodynamics of Finasteride. Clinical Pharmacokinetics. 30(1):16–27. Available at: https://doi.org/10.2165/00003088-199630010-00002

As a result, the frequency of finasteride dosing can be reduced to 1 mg three times per week or 0.5 mg every other day (once steady-state suppression has been achieved) while maintaining sufficient DHT inhibition for significant hair growth effects.

This has the potential to reduce finasteride-associated side effects, particularly sexual side effects associated with hormonal changes.

• Switching to a topical finasteride

Topical, as opposed to oral, formulations deliver the drug directly to the scalp without extensive systemic circulation and therefore reduce overall drug exposure.

Randomized clinical trials have been carried out to assess the effectiveness of oral vs topical finasteride. These have demonstrated comparable clinical benefits, including hair count, hair thickness, and size of bald area.^[28]Hajheydari, Z., Akbari, J., Saeedi, M., Shokoohi, L. (2009). Comparing the Therapeutic Effects of Finasteride Gel and Tablet in Treatment of the Androgenetic Alopecia. Indian Journal of Dermatology, … Continue reading,^[29]Bhura, M. (2013). Comparative Analysis of Topical and Oral Finasteride in Androgenetic Alopecia: Impact on Hair Growth, Systemic Absorption, and Adverse Effects. Indian Journal of Basic and Applied … Continue reading

Topical application lowers the amount of systemic drug, resulting in reduced side effects. Studies have shown that sexual side effects, in particular, are improved when using finasteride topically instead of orally.^[30]Piraccini, B.M., Blume-Peytavi, U., Scarci, F., Jansat, J.M., Falqués, M., Otero, R., Tamarit, M.L., Galván, J., Tebbs, V., Massana, E., Topical Finasteride Study Group. (2022). Efficacy and Safety … Continue reading

The beneficial effects of topical finasteride require consistent, measured application and strong adherence to the prescribed application regimen. As such, users who are not experiencing side effects may find it easier to use oral finasteride instead.

• Using PDE5 inhibitors to manage sexual side-effects

PDE5 inhibitors can be used to treat erectile dysfunction by relaxing the blood vessels so as to allow increased blood flow into the penis. The effectiveness of these drugs is well studied, and they have also been shown to improve erectile function specifically in men taking finasteride.^[31]Casabé, A., Roehrborn, C.G., Da Pozzo, L.F., Zepeda, S., Henderson, R.J., Sorsaburu, S., Henneges, C., Wong, D.G. & Viktrup, L. (2014). Efficacy and Safety of the Coadministration of Tadalafil … Continue reading

While PDE5 inhibitors improve erectile performance and sexual confidence, they do not address other sexual side effects of finasteride, such as libido or ejaculatory volume. In addition, as prescription medications, they should only be used under clinical supervision to reduce the risk of drug interactions.

Final Thoughts

Finasteride does not lower testosterone. In fact, clinical evidence consistently demonstrates that the reduced conversion of testosterone into DHT causes a modest increase in serum testosterone, which remains within the normal physiological ranges. Concerns about finasteride causing testosterone deficiency are therefore not supported by the scientific literature.

Sexual side effects, while real, occur only in a small minority of users and are unlikely to be caused by changes in testosterone. Instead, they are more likely linked to DHT depletion in androgen-sensitive tissues, altered neurosteroid signaling, androgen distribution, or the “nocebo” effect. 

For most users, finasteride is effective and well-tolerated. For those who do experience side effects, strategies like dose adjustment or switching to topical use under the guidance of your physician may improve tolerability while maintaining benefits.