Will I notice changes in my body if I start taking dutasteride?

Dutasteride works by inhibiting the enzyme 5-alpha-reductase, which lowers levels of dihydrotestosterone (DHT), a hormone involved in prostate growth and in androgenetic hair loss. Because it is taken daily and long term, people often want to know what changes to expect. Prescribing information and published studies describe both intended effects and possible side effects, and the two are worth separating.

Expected changes

Dutasteride is approved for the treatment of benign prostatic hyperplasia (BPH). By reducing DHT levels, prostate volume decreases gradually, which the label and clinical trials link to relief of symptoms such as difficulty urinating, weak urinary flow, and frequent night-time urination. Trial data indicate these effects generally take several months — commonly cited as 3 to 6 months — to become noticeable.

In people with androgenetic alopecia (male pattern hair loss), reducing DHT is reported to slow hair loss. Some randomised studies suggest dutasteride may produce greater hair-count increases than finasteride, though head-to-head evidence is limited and dutasteride is not approved for hair loss in most countries. Any such effect is not immediate and is generally reported over several months of continuous use.

Possible side effects

Prescribing information and post-marketing studies describe side effects that mainly concern sexual function and, more recently, mood.

Effects on sexual function

5-alpha-reductase inhibitors, including dutasteride, are associated in their labelling with adverse sexual effects. The most commonly listed are decreased libido, erectile dysfunction, and ejaculation disorders. The manufacturer's first-year label data report erectile dysfunction in roughly 5% of users and decreased libido in roughly 3%, with reported ranges in the literature of about 5-8% and 2-6% respectively. These effects are generally described as reversible on stopping the medicine, and their reported frequency falls with longer use. Some users report that symptoms persist after stopping; the frequency and mechanism of this are disputed and not established.

Impact on mental health

A Swedish register-based cohort study of 2,236,876 men aged 50-90 (Garcia-Argibay et al., JAMA Network Open, 2022) reported an increased risk of a depression diagnosis among users of 5-alpha-reductase inhibitors: hazard ratio 1.68 (95% CI 1.43-1.96) for dutasteride and 1.61 (95% CI 1.48-1.75) for finasteride — that is, about a 68% higher relative risk for dutasteride users compared with non-users. The same study found no association with completed suicide (dutasteride HR 0.98, 95% CI 0.62-1.54). This is observational data and cannot establish cause, but the authors concluded that prescribers and users should be aware of the possible depression risk. An earlier Canadian cohort study (Welk et al., JAMA Internal Medicine, 2017) similarly reported increased self-harm and depression, concentrated in the first 18 months of use, with no increase in suicide.

Note: The European Medicines Agency (EMA) has reviewed finasteride- and dutasteride-containing medicines because of concerns about suicidal thoughts and behaviour. Suicidal ideation has been added as a side effect of unknown frequency to some finasteride-containing products, and regulators have asked manufacturers to remind patients to report mood changes.

Community Feedback:

Community users report a range of changes after starting dutasteride. On the positive side, some describe visible hair growth within about three months on the standard 0.5 mg daily dose, and increased hair thickness or density, including after finasteride had not worked for them. Some also mention a rise in blood testosterone; studies do report a modest average increase in serum testosterone with 5-alpha-reductase inhibition, and it is a consequence of the drug's mechanism rather than a benefit in itself.

Users also report negative effects. One described reduced semen volume and genital numbness after switching from finasteride to dutasteride, and stopped treatment. An initial shedding phase is frequently described in community posts — users often say it settles and is followed by better results — but this is anecdotal and not something the label or trial data quantify. Reduced libido and mild pelvic discomfort are also reported, sometimes described as easing over time. These are individual accounts, not study results.

Talk to a doctor

Dutasteride is a prescription medicine. Talk to a doctor or pharmacist before starting, stopping or combining dutasteride, and report any persistent sexual side effects or changes in mood while taking it. The label also warns that women who are or may become pregnant should not handle leaking capsules, because 5-alpha-reductase inhibitors can harm a developing male fetus, and that men should not donate blood during treatment or for six months after stopping.

References

MedlinePlus. (n.d.). Dutasteride. Retrieved February 20, 2025, from https://medlineplus.gov/spanish/druginfo/meds/a603001-es.html

Garcia-Argibay, M., Hiyoshi, A., Fall, K., & Montgomery, S. (2022). Association of 5alpha-Reductase Inhibitors With Dementia, Depression, and Suicide. JAMA Network Open, 5(12), e2248135. PMID 36547981. https://pubmed.ncbi.nlm.nih.gov/36547981/

Welk, B., McArthur, E., Ordon, M., Anderson, K. K., Hayward, J., & Dixon, S. (2017). Association of Suicidality and Depression With 5alpha-Reductase Inhibitors. JAMA Internal Medicine, 177(5), 683-691. PMID 28319231. https://pubmed.ncbi.nlm.nih.gov/28319231/

Martinez-Salamanca, J. I., & Carballido-Rodriguez, J. (2016). Efectos secundarios de los inhibidores de la 5-alfa-reductasa. Revista Mexicana de Urologia, 76(4), 252-257. https://www.elsevier.es/es-revista-revista-mexicana-urologia-302-articulo-efectos-secundarios-inhibidores-5-reductasa-S2007408516300611

Instituto de Evaluacion de Tecnologias en Salud e Investigacion. (2018). Finasterida en el tratamiento de la alopecia androgenica masculina. EsSalud. https://www.essalud.gob.pe/ietsi/pdfs/farmacoytecno/CS010_2018_Finasterida.pdf

Arias-Santiago, S., & Camacho-Martinez, F. M. (2016). Adverse effects of 5-alpha-reductase inhibitors in male pattern hair loss: is there cause for concern? Actas Dermo-Sifiliograficas, 107(9), 709-711. https://www.actasdermo.org/es-efectos-adversos-inhibidores-5-alfa-reductasa-alopecia-articulo-S0001731016302356

Veterans Health Administration. (n.d.). Dutasteride. Veterans Health Library. Retrieved February 20, 2025, from https://www.veteranshealthlibrary.va.gov/spanish/MedicationsVA/203%2Ca603001es

Memorial Sloan Kettering Cancer Center. (n.d.). Dutasteride and Tamsulosin. Retrieved February 20, 2025, from https://www.mskcc.org/cancer-care/patient-education/medications/adult/dutasteride-and-tamsulosin