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This article summarizes published evidence — FDA-approved drug labeling, published meta-analyses, and pharmacovigilance data, each cited below. It is written by journalists, not clinicians, and has not been reviewed by a physician. Talk to a doctor or a board-certified dermatologist before starting or stopping any treatment. Full medical disclaimer.
This page reports adverse events that regulators and researchers have recorded, including depression and suicidal ideation, because they appear in an FDA-approved label and in an FDA safety communication. Reporting that they were recorded is not the same as saying a drug caused them, and this page cannot tell you what any of it means for you. If you are struggling, that is a conversation for a clinician, not a website.
What the status labels on this page mean
- FDA-approved
- The FDA reviewed the evidence and approved this drug for pattern hair loss.
- Off-label
- An FDA-approved drug being prescribed for something other than what it was approved for. Legal and common, but the hair loss use has not been through FDA review.
- Compounded
- Mixed to order by a pharmacy. Not FDA-approved, and not reviewed by the FDA for safety, effectiveness or quality.
What this page found
- In the trials behind the FDA-approved label, sexual adverse events in year one ran 1.8% vs 1.3% for decreased libido and 1.3% vs 0.7% for erectile dysfunction, finasteride against placebo — small absolute differences.[1]
- A meta-analysis of 15 double-blind trials and 4,495 men found a relative risk of 1.66 for sexual adverse effects with finasteride 1 mg. Only the erectile dysfunction subgroup reached statistical significance on its own.[2]
- A JAMA Dermatology review found that none of 34 trial reports gave adequate information on the severity, frequency or reversibility of sexual adverse events, and 76% followed safety for a year or less.[3]
- Post-finasteride syndrome is not a diagnosis in the FDA label. The label does list persistent symptoms under postmarketing reports, which the FDA says cannot establish causation.[1]
- The most concrete danger on this page is not to you: 8 of 62 affected cats died in a study of topical minoxidil exposures in pets.[8]
How to read any of these numbers
Three things make side effect figures in this category harder to read than they look, and they are worth holding on to before any of the numbers below.
- Placebo groups report side effects too. In the finasteride trials, 1.3% of men taking a dummy pill reported decreased libido.[1] The number that matters is the difference between arms, not the number on the drug.
- Trial populations are not you. The pivotal finasteride trials enrolled men aged 18 to 41.[1] A review of real-world prescribing found only 31% of 5,704 men actually taking the drug at one center would have qualified for those trials.[3]
- Absence of evidence is not evidence of absence. Several questions people most want answered — especially about persistence after stopping — are not answered by the trials, and that is a limitation researchers have themselves published about.
Finasteride: the rates in the FDA-approved label
These are the year-one figures from the controlled trials summarized in the label for the 1 mg tablet FDA-approved, comparing 945 men on finasteride with 934 on placebo.[1]
| Adverse event, year 1 | Finasteride 1 mg | Placebo |
|---|---|---|
| Decreased libido | 1.8% | 1.3% |
| Erectile dysfunction | 1.3% | 0.7% |
| Ejaculation disorder | 1.2% | 0.7% |
| Discontinued because of a sexual adverse event | 1.2% | 0.9% |
The label adds two things that rarely make it into summaries. Rates declined to 0.3% or less by year five, and reported symptoms resolved in men who stopped the drug and also in most of those who continued taking it.[1]
What that does and does not mean. On these numbers, roughly one to two men in a hundred reported a sexual side effect in year one, against roughly one in a hundred on placebo. That is the honest framing of the absolute risk. It is not the same as saying the difference is meaningless to the person it happens to.
What the meta-analysis added
What the trial found
Lee S, Lee YB, Choe SJ, Lee WS. Acta Dermato-Venereologica, 2019
- Design
- Systematic review and meta-analysis of double-blind randomized trials
- Participants
- 15 trials, 4,495 men
- Main result
- Relative risk of sexual adverse effects versus placebo: 1.57 for 5-alpha-reductase inhibitors overall (95% CI 1.19–2.08) and 1.66 for finasteride 1 mg daily (1.20–2.30). Broken down: erectile dysfunction 1.99 (1.10–3.60, significant); decreased libido 1.40 (0.87–2.27, not significant); ejaculation difficulty 1.59 (0.76–3.29, not significant). Dutasteride 0.5 mg: 1.37 (0.81–2.32, not significant).[2]
Stated limitation: Relative risk describes proportional change, not absolute risk. A relative risk of 1.66 applied to a baseline of about 1% is still a small absolute number. Two of the three individual symptom categories did not reach statistical significance.
Source: published systematic review and meta-analysis[2].
The finding that reframes all of the above
A review of how well those trials reported safety at all
A 2015 JAMA Dermatology analysis reviewed 34 clinical trial reports of finasteride for hair loss and found that not one provided adequate information on the severity, frequency or reversibility of sexual adverse events against a clear toxicity grading scale.[3]
76% (26 of 34) of the trials followed safety for one year or less.[3]
And only 31% of 5,704 men actually prescribed the drug at one medical center would have met the eligibility criteria of the pivotal trials.[3]
Belknap et al., JAMA Dermatology, 2015, as summarized by Northwestern Medicine.
This is not an argument that finasteride is dangerous. It is a statement about what the evidence base can and cannot support. If someone tells you confidently that side effects always resolve, or that they never do, the trials underlying that claim were not designed to answer it.
Post-finasteride syndrome, stated precisely
First, what the term means. Post-finasteride syndrome, usually shortened to PFS, is the name used in patient communities for sexual, mood or cognitive symptoms that people report continuing after they have stopped taking the drug. It is not a diagnosis in the FDA-approved label, and there is no agreed diagnostic definition or test for it. That is a statement about the state of the evidence, not a statement that nobody has these experiences.
This is the most contested topic in the category, so here is exactly what each source says, without interpretation stacked on top.
| Source | What it says |
|---|---|
| FDA-approved label[1] | Under Postmarketing Experience, lists continued sexual dysfunction after discontinuation — including erectile dysfunction, and libido, ejaculation and orgasm disorders — plus male infertility and/or poor semen quality, depression, and suicidal ideation. The FDA states postmarketing reports are voluntary, come from a population of uncertain size, and cannot reliably establish causation. |
| FAERS pharmacovigilance analysis[4] | Across 11,557 reports where finasteride was the primary suspect drug, disproportionality signals were high: erectile dysfunction ROR 144.15 (n=3,377), sexual dysfunction ROR 220.84 (n=2,160), libido decreased ROR 119.46 (n=1,476). The authors state directly that pharmacovigilance does not demonstrate a biological causal relationship and that signals may reflect reporting bias. |
| JAMA Dermatology review[3] | The original trials did not report safety data adequately enough to establish whether adverse events persist. |
The honest summary. Post-finasteride syndrome is not a recognized diagnosis in the FDA label. Persistent symptoms after stopping are listed in that label as postmarketing reports, and large numbers of such reports exist in the FDA’s adverse event database. Neither the regulator nor the researchers who analysed those reports claim they prove the drug caused them, and the underlying trials were not built to answer the question. Anyone who tells you this is definitively settled in either direction is going beyond the published evidence.
Pregnancy: the one absolute warning
This is the least ambiguous safety statement in the whole category. Finasteride reduces DHT, and DHT is required for normal development of the external genitalia in a male fetus. The FDA label states finasteride can cause abnormalities of the external genitalia of a male fetus, that PROPECIA is not indicated for use in women, and that women who are or may become pregnant should not handle crushed or broken tablets because of possible absorption through the skin.[1] Intact tablets are film-coated, so ordinary handling is not the concern.
The FDA’s 2025 alert on compounded topical finasteride Compounded raised the same issue for topicals, advising prescribers to educate patients about risks including those arising from handling the product and transference to women.[10] A compounded topical does not have a tablet’s protective coating.
Topical minoxidil: what the label warns about
The FDA-approved Drug Facts label FDA-approved for Women’s Rogaine 5% lists these warnings:[5]
- Extremely flammable — keep away from fire or flame.
- May cause unwanted facial hair growth.
- Not for use under 18 years of age.
- May be harmful if used when pregnant or breastfeeding.
- If you stop, normal hair loss restarts and you will likely lose newly grown hair within three to four months.
In the head-to-head trial of 5% against 2% in men, itching and local irritation were more common at 5%, and in the equivalent trial in women, itching, local irritation and hypertrichosis were all increased at 5%. We cover both trials in our minoxidil formats guide.
The early shedding many people experience when starting minoxidil — sometimes called a “dread shed” — is not described as a distinct phenomenon in the FDA-approved label, and we could not obtain a primary source quantifying how often it happens or how long it lasts. We are therefore not putting a figure on it.
Oral minoxidil: off-label, and why the boxed warning is confusing
Minoxidil tablets Off-label are FDA-approved for resistant high blood pressure, not hair loss. That label carries a boxed warning about pericardial effusion progressing to tamponade and possible worsening of angina, and it describes hypertrichosis in about 80% of patients.[6]
Read the boxed warning in context. The approved dose range on that label is 10 to 40 mg per day, up to 100 mg — a blood-pressure dose. Low-dose oral minoxidil for hair is typically a small fraction of that. Quoting the boxed warning as if it applied unchanged at hair-loss doses is misleading; so is pretending the tablet has no cardiovascular profile at all.
What the trial found
Vañó-Galván S, et al. Journal of the American Academy of Dermatology, 2021
- Design
- Multicenter safety study
- Participants
- 1,404 patients (943 women, 461 men), median age 43
- Main result
- Hypertrichosis 15.1%; lightheadedness 1.7%; fluid retention 1.3%; tachycardia 0.9%; headache 0.4%; periorbital oedema 0.3%; insomnia 0.2%. No severe adverse events. Discontinuation 1.7% overall.[7]
Stated limitation: This is a safety study, not a randomized efficacy trial, and it does not establish that the treatment works. The authors state that low-dose oral minoxidil remains an off-label treatment.
Source: published multicenter study[7].
The warning almost nobody gives you: minoxidil and pets
If you have a cat, read this before you buy topical minoxidil. A study of 211 topical minoxidil exposures in dogs and cats found 87 animals developed clinical signs (62 cats, 25 dogs). Of the cats that developed signs, 8 of 62 died. Cats were typically exposed accidentally — licking an owner’s treated skin or a pillowcase, or being splashed during application.[8]
The American Academy of Dermatology states that a few drops can make a cat sick enough to require life-saving emergency veterinary care, lists loss of appetite, vomiting, difficulty breathing and lethargy as signs, and notes onset can occur within 30 minutes.[9] Its practical advice: store it securely, keep pets away from treated areas, wash your hands thoroughly, do not let pets touch your scalp, dispose of contaminated items properly, and never apply human minoxidil to an animal. If exposure happens, the AAD directs people to call a veterinarian or the ASPCA Poison Control line immediately.[9]
The AAD page cites a follow-up of 68 exposed cats with 10 deaths, which differs from the 62 cats and 8 deaths in the 2021 study. We have quoted the figures from the primary study above and cited the AAD separately rather than merging two different counts into one number.
Compounded topical finasteride: a separate risk profile
Products in this category Compounded are not FDA-approved and have not been evaluated by the FDA for safety, effectiveness or quality. In April 2025 the FDA published a safety communication describing 32 adverse event reports received between 2019 and 2024, listing erectile dysfunction, anxiety, suicidal ideation, brain fog, depression, fatigue, insomnia, decreased libido, testicular pain, and local reactions.[10]
The same document notes that some prescribers had falsely stated there was no risk of any adverse event because the product was topical.[10] If a service tells you that, the regulator has already addressed it. We go through the trial data and the alert in detail in our oral versus topical guide.
When to stop reading and talk to someone
Nothing on this page can tell you whether something you are experiencing is caused by a drug. These are the situations where a clinician, not an article, is the right next step:
- Any new sexual, mood or cognitive symptom that started after beginning treatment — including low mood or thoughts of self-harm, which appear in the label’s postmarketing section and should be raised promptly.
- Chest pain, unusual shortness of breath, a racing heart, or swelling, particularly on oral minoxidil.
- Persistent scalp irritation, rash or burning that does not settle.
- Any possibility of pregnancy in a household where finasteride is used, especially a compounded topical.
- A pet that has been near a treated area and is not itself — that one is a call to a vet, not a doctor.
Side effects are a conversation, not a search result
Whether a symptom is related to a drug, and what to do about it, needs someone who knows your history. Sesame Care is a US marketplace that lists upfront cash prices for consultations before you book, including hair loss visits — useful if you do not have a dermatologist and want to price the conversation first.
Sesame Care is a US telehealth marketplace that lists upfront cash prices for appointments. The link below is an affiliate link: if you book, we may earn a commission at no extra cost to you.
See consultation prices →Where to go next
Frequently asked questions
How common are sexual side effects with finasteride?
In the first year of the trials in the FDA-approved label, decreased libido was reported by 1.8% on finasteride versus 1.3% on placebo, erectile dysfunction by 1.3% versus 0.7%, and ejaculation disorder by 1.2% versus 0.7%. The label also states these rates declined to 0.3% or less by year five. A separate meta-analysis of 15 double-blind trials covering 4,495 men found a relative risk of 1.66 for sexual adverse effects overall.
Is post-finasteride syndrome real?
It is not a recognized diagnosis in the FDA-approved label. The label does list, under postmarketing experience, continued sexual dysfunction after discontinuation, along with depression and suicidal ideation – but the FDA notes postmarketing reports are voluntary, come from a population of unknown size, and cannot establish causation. A 2015 JAMA Dermatology review separately concluded that the original trials did not report safety data well enough to answer the question of persistence.
Do finasteride side effects go away?
The FDA-approved label states that reported sexual adverse events resolved in men who discontinued the drug, and also in most of those who continued taking it. The same label separately lists postmarketing reports of symptoms continuing after discontinuation. Both statements are in the label; neither one settles the question for any individual.
Is minoxidil dangerous for pets?
Yes, and this is under-reported. A study of 211 topical minoxidil exposure cases in dogs and cats found 87 animals developed clinical signs, and 8 of the 62 affected cats died. The American Academy of Dermatology states that a few drops can make a cat sick enough to need emergency care. Cats are typically exposed by licking an owner’s skin or a pillowcase after application.
Is oral minoxidil safe for hair loss?
It is off-label – minoxidil tablets are approved for resistant high blood pressure, at much higher doses, and that label carries a boxed warning about pericardial effusion. The largest safety study of low-dose oral minoxidil for hair, in 1,404 patients, reported hypertrichosis in 15.1%, other effects at under 2% each, and no severe adverse events. Its authors state clearly that the use remains off-label.
Can finasteride affect a pregnancy?
Finasteride can cause abnormalities of the external genitalia of a male fetus. The FDA label states the drug is not indicated for use in women, and that women who are or may become pregnant should not handle crushed or broken tablets. The FDA’s 2025 alert on compounded topical finasteride specifically flagged risks arising from handling the product and transference to women.
Sources
- U.S. Food and Drug Administration. PROPECIA (finasteride) tablets, prescribing information. 2022. accessdata.fda.gov
- Lee S, Lee YB, Choe SJ, Lee WS. Adverse sexual effects of treatment with finasteride or dutasteride for male androgenetic alopecia: a systematic review and meta-analysis. Acta Derm Venereol. 2019. medicaljournals.se
- Belknap SM, West DP, Brannigan R, Nardone B, et al. Adverse event reporting in clinical trials of finasteride for androgenic alopecia: a meta-analysis. JAMA Dermatol. 1 April 2015. Summarized by Northwestern Medicine: news.feinberg.northwestern.edu
- Zhong X, Yang Y, Wei S, Liu Y. Multidimensional assessment of adverse events of finasteride: a real-world pharmacovigilance analysis based on FAERS from 2004 to April 2024. PLOS ONE, 2025. journals.plos.org
- U.S. Food and Drug Administration. Women’s ROGAINE 5% Minoxidil Topical Aerosol, Drug Facts label. 2019. accessdata.fda.gov
- U.S. Food and Drug Administration. LONITEN (minoxidil) tablets, prescribing information. 2015. accessdata.fda.gov
- Vañó-Galván S, et al. Safety of low-dose oral minoxidil for hair loss: a multicenter study of 1404 patients. J Am Acad Dermatol. 2021;84(6):1644-1651. PMID 33639244.
- Tater KC, Gwaltney-Brant S, Wismer T. Topical minoxidil exposures and toxicoses in dogs and cats: 211 cases (2001-2019). J Am Anim Hosp Assoc. 2021;57(5):225-231. PMID 34370845.
- American Academy of Dermatology. Minoxidil can be toxic to cats and dogs. Updated 17 August 2026. aad.org
- U.S. Food and Drug Administration. FDA alerts health care providers, compounders and consumers of potential risks associated with compounded topical finasteride products. 22 April 2025. fda.gov
Affiliate disclosure: this page contains affiliate links. We may earn a commission when you buy through them, at no additional cost to you. Commissions never determine what we cover or what the evidence sections say. Read our full affiliate disclosure.
How we researched this: every figure on this page is sourced to a numbered reference below. For this article those sources are FDA-approved drug labeling, an FDA safety communication, published meta-analyses and safety studies, an FAERS pharmacovigilance analysis, and guidance from the American Academy of Dermatology. Where a figure could not be verified from a primary source, we say so in the text rather than estimating. We do not test products and we do not practice medicine. See our review methodology.
