Topical Finasteride Safety: Yu 2026 Research Summary
This is a plain-language summary of the original published research. We do not add conclusions or opinions of our own. This is not medical advice — consult a certified healthcare practitioner before making any decision.
Original research published in JMIR Dermatology, 2026
Patient Satisfaction, Side Effects, and Other Reactions Reported by Adult Men Prescribed Compounded Topical Finasteride via a National Telehealth Platform: Retrospective Analysis of Real-World Data
Study conclusion
In the largest real-world safety study of compounded topical finasteride to date, sexual side effects were reported by just 12 of 638,629 men (0.002%), and no patients stopped treatment due to side effects. The most common reactions were scalp irritation and dizziness, most likely caused by the topical application and the minoxidil component respectively. Note: this study was funded by Hims & Hers, whose employees authored the research and who sell the products studied, which limits how much weight can be placed on these findings.
Strength of evidence
Based on a single retrospective study with no control group. The entire author team is employed by or serves as paid advisors to Hims & Hers, which funded the study and sells the products analysed, introducing a strong potential for positive-result bias. Only 23.7% of patients completed the follow-up check-in, likely skewing toward more satisfied patients. Despite the extraordinary sample size, these limitations prevent drawing causal conclusions.
Who it applies to
Who was studied
Adult men with pattern hair loss (hair loss caused by genetics and hormones) who were prescribed a compounded topical finasteride and minoxidil product via the Hims & Hers telehealth platform between April 2021 and April 2025. Mean age was 39.6 years. All 638,629 patients in the sample were male. The products studied were 0.3% topical finasteride combined with minoxidil, dispensed as a spray or serum applied to the scalp once daily.
Who was NOT studied
Women were not included. Men who stopped treatment early or did not engage with the platform after starting may be underrepresented, as only 23.7% completed the follow-up check-in. The study cannot be applied to oral finasteride, FDA-approved topical finasteride products, or compounded formulations at different concentrations. Men who reported side effects to their own doctors outside the platform would not have been captured in this data.
What to look for when shopping
The most commonly reported reactions were scalp irritation (likely from the topical route) and dizziness, fast heart rate, and headache (likely from the minoxidil component, which affects blood vessels). These are the side effects most worth monitoring in the first few months of use. Because the products studied combine both topical finasteride and minoxidil, it is not possible to say with certainty which ingredient caused a given side effect.
What research cannot help you decide
Because there was no control group, this study cannot prove that any reported side effect was caused by the product rather than occurring by chance in a large population. The combination product means side effects cannot be attributed to topical finasteride specifically. The low response rate to the check-in means satisfied patients may be overrepresented, and true side effect rates could be higher than reported. The study also cannot tell you whether side effects would be the same with FDA-approved or differently formulated topical finasteride products.
Key findings
- 80.4% of patients who completed a follow-up check-in reported being satisfied with their treatment.
- 2.7% of patients who completed the check-in reported experiencing a side effect of any kind.
- Only 0.04% of all 638,629 patients proactively messaged their care team about a side effect or medication reaction.
- The most reported reactions were scalp irritation (0.007%), dizziness (0.005%), and increased heart rate (0.003%).
- Sexual side effects (reduced libido or erectile dysfunction) were reported by just 12 of 638,629 patients (0.002%).
- No patients discontinued treatment or sought emergency care due to a side effect during the study period.
What they did
Hims & Hers researchers conducted a retrospective analysis of patient data collected between April 2021 and April 2025 from their own telehealth platform. Patients with pattern hair loss who were prescribed a compounded topical finasteride and minoxidil product were included. No control group was used, as all patients analysed were actively taking the treatment.
Two data sources were used. First, a follow-up check-in was sent to patients approximately 130 days after starting treatment. This check-in asked two yes/no questions: whether the patient was satisfied with treatment and whether they were bothered by side effects. Second, unprompted messages that patients sent to their care team at any time were reviewed for reports of side effects. A clinical quality team monitored messages in real time and validated which reports related to the finasteride or minoxidil products.
The study was approved by an institutional review board and data were de-identified before analysis. The research was funded by Hims & Hers, and all six authors are employees of or paid advisors to that company. The company had no formal role in the study design or analysis according to the authors, but the financial relationship represents a meaningful conflict of interest.
What they found
| Comparison | Result | Significant? |
|---|---|---|
| Treatment satisfaction (check-in respondents, n=151,352) | 80.4% reported being satisfied with treatment | Yes |
| Any side effect (check-in respondents, n=151,352) | 2.7% reported experiencing a side effect of any kind | Yes |
| Any side effect (all patients, n=638,629) | 0.04% proactively messaged their care team about a side effect | Yes |
| Scalp irritation (all patients, n=638,629) | 0.007% reported scalp irritation | Yes |
| Dizziness (all patients, n=638,629) | 0.005% reported dizziness | Yes |
| Sexual side effects (all patients, n=638,629) | 0.002% reported reduced libido or erectile dysfunction (12 of 638,629 patients) | Yes |
| Depression (all patients, n=638,629) | 0.002% reported depression (13 of 638,629 patients) | Yes |
| Treatment discontinuation due to side effects | 0% — no patients discontinued or sought emergency care due to a side effect | Yes |
Limitations
- 1.Retrospective study with no control group: side effects cannot be causally attributed to the product.
- 2.Only 23.7% of patients completed the follow-up check-in, likely skewing results toward more satisfied patients with fewer side effects.
- 3.The products studied combine topical finasteride and minoxidil: side effects cannot be attributed to either ingredient specifically.
- 4.Patients who reported side effects to outside healthcare providers were not captured.
- 5.Entire author team is employed by or serves as paid advisors to the company that funded the study and sells the products analysed.
Who funded it
Funded by Hims & Hers Health, Inc., which sells the products studied. All six authors are full-time employees of or paid advisors to Hims & Hers Health, Inc. The authors state the company had no role in study design, data analysis, or publication decisions.
Used in these articles
Links added as fact-checks and articles citing this study are published.