Finasteride Side Effects: What the Numbers Actually Say

Reviewed by LPMD Medical Group cliniciansUpdated 2026-09-136 min read

The short answer

In the finasteride 1 mg trials, 3.8 percent of men reported a sexual side effect in the first year versus 2.1 percent on placebo: decreased libido 1.8 vs 1.3 percent, erectile dysfunction 1.3 vs 0.7 percent, and ejaculation disorder 1.2 vs 0.7 percent. Since then, regulators have added depression, suicidal ideation, breast changes and sexual dysfunction that persists after stopping to the label based on reports whose frequency cannot be reliably estimated. The risk is small for most men and real for some, and mood changes or suicidal thoughts mean stop and get help.

There are two finasteride internets. In one, the side effects are a myth invented by anxious men and the pill is basically a vitamin. In the other, one tablet ends your sex life by Tuesday. Both camps have screenshots. Neither has a denominator.

We take the medicine seriously, which means taking the numbers seriously, including the ones nobody has.

Key facts

In the one-year trials, 3.8 percent of men on finasteride 1 mg reported a sexual side effect versus 2.1 percent on placebo ¹.
Across 15 placebo-controlled trials, finasteride carried about 1.66 times the risk of sexual dysfunction compared with placebo ⁴.
Depression, suicidal ideation, breast changes and sexual dysfunction persisting after stopping were added from post-approval reports, whose frequency cannot be reliably estimated ¹².
In 2025, European regulators concluded suicidal thoughts are a side effect of finasteride with unknown frequency and added a patient card to 1 mg packs ³.
Finasteride lowers PSA, may increase the risk of high-grade prostate cancer, and must never be handled crushed or broken by anyone who is or may become pregnant ¹.

What are the finasteride side effect rates versus placebo?

Small, and the placebo column matters. The label’s 12-month trials had 945 men on finasteride and 934 on placebo ¹.

Side effect, year 1	Finasteride 1 mg	Placebo
Decreased libido	1.8%	1.3%
Erectile dysfunction	1.3%	0.7%
Ejaculation disorder	1.2%	0.7%
Any of the above	3.8%	2.1%
Stopped the trial because of them	1.2%	0.9%

Pooling more trials does not change it. A meta-analysis of 15 placebo-controlled trials with 4,495 participants found a relative risk of sexual dysfunction of 1.66 for finasteride 1 mg versus placebo ⁴: a real increase on a low baseline.

The label adds two reassurances. Sexual side effects resolved in men who discontinued because of them and in most who continued, and in years 2 through 4 finasteride and placebo did not differ significantly in rates of impotence, decreased libido or ejaculation disorder ¹.

Do finasteride sexual side effects persist after stopping?

Sometimes, and nobody can honestly tell you how often. After approval, men reported erectile, libido, ejaculation and orgasm disorders that continued after stopping, and the label lists them, noting that voluntary reports allow neither a reliable frequency estimate nor proof of cause ¹.

The evidence for persistence comes from case series and records. Irwig and Kolukula interviewed 71 otherwise healthy men aged 21 to 46 whose new sexual symptoms had lasted at least 3 months after stopping; 94 percent reported low libido, 92 percent erectile dysfunction, and symptoms had averaged 28 to 40 months ⁵. A 2017 electronic-records study of 11,909 men exposed to finasteride or dutasteride found erectile dysfunction persisting more than 90 days after stopping in 1.4 percent; of 530 men with new erectile dysfunction, 19.4 percent had it persist, and young men exposed more than 205 days had about 4.9 times the risk ⁶.

What tempers those findings is the trial data: resolution in most men and no difference from placebo after year one ¹. The case series had no control group and enrolled men who already believed finasteride had harmed them; the trials did not follow men after they stopped. Reporting also rose after the 2012 label change and its publicity, which may reflect awareness as much as incidence ⁸. The label’s wording, that frequency and cause cannot be reliably established, is the honest summary ¹. See the finasteride page for how we screen and follow men on it.

Can finasteride cause depression or suicidal thoughts?

The regulators now say yes, with the frequency unknown. In August 2022 the FDA approved a labeling change adding suicidal ideation and behavior, plus additional sexual and psychoneurocognitive adverse events, to the finasteride 1 mg label ². In May 2025 the European Medicines Agency concluded that suicidal ideation is a side effect of finasteride 1 mg and 5 mg with unknown frequency, and required a patient card in 1 mg packs telling men to stop and contact a doctor if their mood changes ³. The EMA also noted that sexual side effects may themselves contribute to mood changes ³.

The population data are mixed. A Canadian cohort of 93,197 men aged 66 and older who started a 5-alpha reductase inhibitor for prostate enlargement found no increase in completed suicide, but self-harm was about 1.9 times more likely in the first 18 months, and depression about 1.9 times more likely in that window and 1.2 times afterward, with small absolute increases ⁷. A WHO pharmacovigilance analysis found 356 suicidality reports and a signal concentrated in younger men taking finasteride for hair loss rather than older men with prostate disease ⁸.

What are the breast, PSA, prostate and pregnancy warnings?

Breast tenderness and enlargement and male breast cancer have been reported since approval, so any new breast lump, pain, nipple discharge or enlargement gets evaluated rather than watched ¹. Testicular pain, infertility or poor semen quality, and hypersensitivity reactions such as rash, hives and facial swelling are on the same list ¹.

Finasteride lowers PSA, the prostate cancer screening test. In the hair loss trials mean PSA fell from 0.7 to 0.5 ng/mL at 12 months, and any confirmed rise from your lowest value should be evaluated even if still in the normal range, so tell any clinician ordering a PSA that you take it ¹. The label also warns that 5-alpha reductase inhibitors may increase the risk of high-grade prostate cancer ¹.

The pregnancy warning is about handling. The danger is to a male fetus, so anyone who is or may become pregnant must never handle crushed or broken tablets; intact tablets are coated, so do not split them or leave fragments around ¹. Semen is a smaller concern: the label puts a partner’s exposure from the highest measured semen level at 650-fold below the dose shown to have no effect on DHT in men ¹.

What should you do if side effects appear?

Do not quietly quit or quietly suffer; both waste information. For low mood, hopelessness, anxiety or any thought of harming yourself, stop the medicine and contact a clinician immediately ³. Suicidal thoughts are an emergency: call or text 988 in the US.

For sexual side effects or testicular pain, message your clinician before changing anything. Because trial-era sexual effects resolved in men who stopped and in most who continued, a common Re-route is a short symptom log and a reassessment a few weeks later ¹. Options after that include stopping, a plan without finasteride, or a lower dose or compounded topical form, both off-label and, in the topical case, not FDA-approved. A breast lump or nipple discharge gets evaluated rather than logged.

When to talk to a clinician

Stop and call for mood changes or suicidal thoughts; breast lumps, pain, nipple discharge or enlargement; rash, hives or swelling of the face or lips; or testicular pain ¹³. Reach out promptly, without necessarily stopping, for changes in libido, erections or ejaculation, so the next step is decided with data rather than dread ¹. Raise an upcoming PSA test, a history of depression, or a partner who is or may become pregnant before the first tablet ¹.

Bring the screenshots from both internets to a $45 consult. We have read them, and we still prefer denominators.

Hairy questions, straight answers

What percentage of men get side effects from finasteride?

In the one-year trials behind the label, 3.8 percent of men on finasteride 1 mg reported one or more sexual side effects versus 2.1 percent on placebo, so the difference attributable to the drug was under 2 percent. A meta-analysis of 15 placebo-controlled trials put the relative risk of sexual dysfunction on finasteride at about 1.66 times placebo. Mood, breast and persistent effects were identified after approval, and their frequency is not established.

Do finasteride side effects go away?

In the trials, sexual side effects resolved in men who stopped finasteride and in most men who kept taking it, and by years 2 to 4 the rates were no different from placebo. Since approval, some men have reported sexual dysfunction that continued after stopping. How often that happens is not known; one electronic-records study found persistent erectile dysfunction in about 1.4 percent of men exposed to a 5-alpha reductase inhibitor.

Is post-finasteride syndrome real?

Persistent sexual, mood and cognitive symptoms after stopping finasteride are reported, listed on the label, and were the subject of an FDA patient listening session. What is unresolved is how often they occur and how much finasteride causes them, because the reports come from voluntary systems and uncontrolled case series and the trials were not designed to look after stopping. Both dismissing it and treating it as common go beyond the evidence.

Can finasteride cause depression or suicidal thoughts?

The FDA added suicidal ideation and behavior to the label in 2022, and in 2025 European regulators concluded suicidal thoughts are a side effect of finasteride with unknown frequency and added a patient card to 1 mg packs. A large Canadian cohort found more self-harm and depression, mostly in the first 18 months, but no increase in completed suicide. If your mood drops or you have thoughts of harming yourself, stop and get help right away.

Does finasteride affect PSA or prostate cancer risk?

Yes on both counts. Finasteride lowers PSA, so any confirmed rise from your lowest value while taking it should be evaluated even if the number is still in the normal range, and any clinician ordering a PSA needs to know you take it. The label also warns that 5-alpha reductase inhibitors may increase the risk of high-grade prostate cancer.

What should I do if I get side effects on finasteride?

For mood changes or suicidal thoughts, stop and contact a clinician right away; call or text 988 in the US if you are in crisis. For sexual side effects, breast changes or testicular pain, message your clinician before making changes so you can decide together whether to continue and reassess, adjust the plan, or stop. Breast lumps, pain or nipple discharge always need evaluation.

Sources

Information checked 2026-09-13 by LPMD Medical Group clinicians. This article is general education, not a diagnosis or a treatment plan for you. Your clinician and pharmacist provide the instructions for your actual prescription.

What are the finasteride side effect rates versus placebo?

Do finasteride sexual side effects persist after stopping?

Can finasteride cause depression or suicidal thoughts?

What are the breast, PSA, prostate and pregnancy warnings?

What should you do if side effects appear?

When to talk to a clinician

Hairy questions, straight answers

Sources

Further up the trail.

Finasteride for Hair Loss: How It Works and What to Expect

Topical Finasteride: Does It Really Cut Side Effects?

Dutasteride vs Finasteride for Hair Loss: Which Is Better?