Finasteride Dosage Guide: Protocols, Calculator & Safety
Everything you need to know about Finasteride dosing — protocols, safety, and where to buy.
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Dosing Protocols
Beginner protocol for androgenetic alopecia (male-pattern hair loss):
Dose: Finasteride 1mg orally once daily, taken at approximately the same time each day. May be taken with or without food. Tablet should be swallowed whole and not crushed or broken (crushed tablets pose handling risk for pregnant women).
Duration before evaluating: 6 months minimum for any meaningful efficacy assessment; ideally 12 months before final judgment. Hair follicle cycling takes months, and visible hair count improvements accumulate slowly. Early "shedding" (weeks 2-8) may occur as terminal hairs exit phase before new growth; this is usually a positive sign rather than failure.
Adjunctive therapy: Topical minoxidil 5% (foam or solution) applied twice daily to affected scalp areas — the evidence is clear that finasteride + minoxidil produces better outcomes than either alone. Start minoxidil concurrently with finasteride; do not delay the adjunct.
Monitoring and informed consent before starting: (1) Discuss with a physician and review informed consent including sexual side effects (~1-3% in RCTs), the post-finasteride syndrome possibility (rare but real), gynecomastia risk, and mood effects. (2) Establish a baseline assessment — photos of scalp/hairline in consistent lighting and angles, self-rating of libido/sexual function, self-rating of mood. (3) At 3 months: check for side effects (sexual, mood, breast), continue if tolerable. (4) At 6 months: photograph and compare to baseline; expect hair count stabilization or early improvement. (5) At 12 months: definitive efficacy assessment. (6) If sexual or psychological side effects develop: discontinue, do not persist through symptoms. (7) If improvement is achieved: continued indefinite therapy is required to maintain benefit; discontinuation reverses gains within 12 months.
Stopping criteria: Any persistent sexual dysfunction, mood symptoms, gynecomastia, or other concerning effects should trigger immediate discontinuation. If discontinuing for lifestyle reasons, expect gradual reversal of hair benefits over 6-12 months as DHT levels normalize.
Intermediate protocols:
For BPH symptom management (labeled use): Finasteride 5mg orally once daily, long-term. Usually combined with an alpha-blocker (doxazosin 2-4mg nightly, or tamsulosin 0.4mg daily) during the first 6-12 months for rapid symptomatic relief while finasteride's prostate-volume-reducing effect develops. Monitoring: baseline PSA, IPSS (International Prostate Symptom Score), uroflowmetry; repeat at 6-12 months. Adjust PSA interpretation by doubling the on-treatment value. Continue indefinitely if tolerated and symptomatically beneficial.
For prostate cancer chemoprevention (off-label, controversial): Some men at elevated prostate cancer risk (strong family history, prior high-grade PIN, elevated PSA without malignancy) consider finasteride 5mg/day based on PCPT data showing ~25% reduction in overall prostate cancer. This is controversial, not FDA-labeled for prevention, and requires detailed urologist-level discussion of the original Gleason-upgrading concern (now largely resolved but still sometimes cited). Not a routine recommendation.
For treatment-resistant androgenetic alopecia: If 12+ months of 1mg/day with topical minoxidil 5% produces inadequate response, options include: (1) Increase finasteride to 1.25-2mg/day (off-label, some case series show incremental benefit); (2) Switch to dutasteride 0.5mg/day which produces greater DHT suppression (~95% vs 70%); (3) Add oral minoxidil 0.25-2.5mg/day for enhanced hair growth effect; (4) Add ketoconazole 2% shampoo 3× weekly; (5) Consider PRP (platelet-rich plasma) or low-level laser therapy adjuncts. Resistant cases warrant dermatologist evaluation for alternative diagnoses (telogen effluvium, traction alopecia, scarring alopecias).
Topical finasteride as alternative to oral: For men wanting hair-loss benefit with minimized systemic side effect risk, topical finasteride 0.25% solution applied 1mL BID to affected scalp areas provides efficacy comparable to oral 1mg/day (Piraccini 2022, Ali 2020). Plasma DHT suppression is ~30-40% with topical versus ~70% with oral, likely correlating with reduced sexual side effect risk. Currently approved in Italy and some other European countries; available via compounding pharmacies in the US. Reasonable first-line for men concerned about oral side effects.
Female post-menopausal hair loss (off-label): Post-menopausal women with androgenetic pattern hair loss may use finasteride 2.5-5mg/day with some evidence of modest hair count benefit. Strict contraception or definitive menopause status is required. Typically prescribed by dermatologists with hormonal/endocrine assessment. Baseline testosterone, DHEA-S, and thyroid labs should be obtained to rule out other causes of androgenic alopecia.
Transgender feminizing therapy adjunct: Some gender-affirming care providers include finasteride 1-5mg/day as adjunctive androgen blockade alongside estradiol and/or spironolactone. The rationale: further suppress residual androgen signaling. This use has grown over the 2020s with some prospective outcome data emerging.
Advanced protocols and specialized contexts:
High-dose and dutasteride-transition strategies: Men with severe, treatment-resistant androgenetic alopecia despite comprehensive therapy (finasteride 1mg + topical minoxidil 5% + ketoconazole) for 18+ months without adequate response may consider transition to dutasteride 0.5mg/day. Dutasteride produces ~95% DHT suppression versus ~70% with finasteride, with correspondingly stronger hair outcomes in meta-analyses. Side effect profile is broader (sexual side effects ~1.5-2× higher); transition should include explicit informed consent about the trade-off. Typical approach: taper off finasteride over 1-2 weeks, then initiate dutasteride 0.5mg daily; evaluate at 6-12 months. Some protocols use dutasteride 0.5mg every other day for somewhat reduced side effects with maintained efficacy.
"Wash in, wash out" protocols — controversial: Some practitioners have used protocols alternating finasteride dosing to reduce cumulative drug exposure while preserving efficacy — e.g., 1mg every other day rather than daily. The pharmacology doesn't clearly support improved tolerability (the irreversible enzyme inhibition persists between doses), but some men find subjective improvements with intermittent dosing. This is not a standard recommendation and efficacy data are limited.
BPH with concurrent erectile dysfunction: Men with BPH who develop or have pre-existing ED face a nuanced choice. Finasteride's low-rate ED risk may be acceptable; alternatively, tadalafil 5mg/day (approved for both BPH and ED) addresses both indications without 5α-reductase effects. For severe BPH with concomitant hair loss interest, finasteride 5mg may address both; for pure BPH with dominant sexual concerns, tadalafil monotherapy may be preferable. Individual discussion required.
Monitoring for hepatic and metabolic changes: Long-term users (>5 years) should have periodic liver function tests, lipid panel, fasting glucose/A1c, and hormonal panel (testosterone, estradiol, DHEA-S). Finasteride is not known to cause lipid or glucose abnormalities routinely, but the "metabolic syndrome" connection to steroid hormones warrants awareness. Baseline + annual comprehensive metabolic panel is reasonable.
Post-finasteride syndrome management: For users developing PFS symptoms, there is no established treatment protocol, and the clinical evidence for any specific intervention is limited. Reported approaches (without strong evidence) include: (1) Neurosteroid replacement — pregnenolone 25-100mg/day, possibly allopregnanolone analogs (though these are not widely available); (2) Exercise therapy — resistance training can modestly improve depression, cognition, and libido in PFS; (3) Mental health support — depression, anxiety, and suicidal ideation in PFS warrant active psychiatric engagement; (4) Time — some PFS cases gradually improve over 1-3 years after discontinuation, though others are persistent; (5) Experimental therapies — various approaches including clomiphene, hCG, testosterone replacement (if T is suppressed), and SARM protocols have been tried anecdotally but lack RCT support. The Foundation for Post-Finasteride Syndrome (PFSfoundation.org) maintains a patient registry and funds research; affected individuals may find this community helpful.
Clinical monitoring framework for chronic use: (1) Baseline (before starting): comprehensive history, sexual function questionnaire (e.g., IIEF for men), depression screening (PHQ-9), PSA (if age >40), testosterone, liver function. (2) 3 months: clinical check-in, side effect screen, continuation assessment. (3) 6 months: photographic assessment (for hair loss), symptom scales (for BPH), sexual function and mood reassessment. (4) 12 months and annually: comprehensive reassessment, labs as indicated, discussion of continuation criteria. (5) Discontinuation planning: anyone considering stopping should have a clear plan — taper vs. abrupt, monitoring for withdrawal-like symptoms, expectations for hair/prostate effect regression.
Commonly Stacked With
Finasteride stacking should be approached with a clear understanding of why you are combining compounds — primarily either hair loss management or BPH/prostate management — and with awareness of the competing hormonal pathway effects.
Minoxidil (topical or oral) — synergistic for hair loss: Minoxidil, the potassium channel opener with vasodilator and hair follicle effects, acts through mechanisms distinct from finasteride (does not affect DHT) and the combination produces clearly additive or synergistic hair-growth effects. The two are frequently prescribed together in comprehensive hair loss regimens — finasteride 1mg PO daily plus minoxidil 5% topical BID is the current gold-standard combination for androgenetic alopecia. Some practitioners use oral minoxidil (0.25-5mg/day) for severe or treatment-resistant cases. The mechanisms are complementary: finasteride halts DHT-driven miniaturization; minoxidil promotes active anagen phase and follicle vascularization.
Ketoconazole (topical 2% shampoo): Topical ketoconazole has mild anti-androgen properties in skin and additional anti-fungal (Malassezia) effects. Adding 2% ketoconazole shampoo 2-3× weekly provides modest incremental hair-loss benefit beyond finasteride/minoxidil and helps with associated seborrheic dermatitis. Evidence is moderate; cost-benefit is favorable.
Dutasteride cautions: Do not combine finasteride with Dutasteride — they are in the same mechanistic class (5α-reductase inhibitors) and combination provides no additional benefit while compounding risk. Users who want more complete DHT suppression should switch entirely from finasteride to dutasteride rather than stack them.
Saw Palmetto — alternative or adjunct: Saw Palmetto extracts have weak 5α-reductase inhibitory effects and are sometimes used as a "natural" alternative to finasteride or as adjunctive therapy. The evidence is mixed (some BPH trials positive, most large well-designed trials negative). Combining saw palmetto with finasteride is safe but unlikely to provide meaningful additive benefit given finasteride's much more potent enzyme inhibition. Saw palmetto may make sense for men using finasteride intermittently or at reduced dosing.
Ashwagandha and adaptogens — caution regarding testosterone: Ashwagandha and other testosterone-supportive adaptogens produce modest testosterone increases. In men on finasteride (where T is already partially elevated from reduced 5α-reduction), this may further increase aromatization and estradiol levels, increasing risk of gynecomastia or mood effects. Not a strict contraindication, but worth monitoring for breast tenderness and mood changes.
Testosterone replacement therapy (TRT) considerations: Men receiving TRT for clinical hypogonadism who also use finasteride will have suppressed DHT (~70%) while having normal or high T. This is physiologically unusual and some practitioners consider it suboptimal — DHT has distinct biological roles and its chronic suppression may contribute to the subset of TRT patients reporting persistent low libido or cognitive symptoms despite normalized testosterone. Options: (1) continue finasteride on TRT to preserve hair; (2) discontinue finasteride on TRT and accept hair loss progression; (3) use topical finasteride to minimize systemic DHT effects while preserving some scalp effect; or (4) switch to dutasteride if greater hair benefit is prioritized over DHT preservation. Individual decision.
DHEA and pregnenolone: DHEA and Pregnenolone are upstream steroid precursors. DHEA could theoretically increase substrate for 5α-reductase, though the finasteride-induced enzyme block limits downstream DHT effects. Some PFS-affected individuals have used pregnenolone/allopregnanolone-boosting strategies to attempt neurosteroid restoration, with anecdotal but unproven benefit.
Vitamins and cofactors: Zinc, biotin, iron (if deficient), and vitamin D are frequently included in comprehensive hair-loss regimens. Zinc has weak 5α-reductase inhibition in vitro but clinical effect is minimal. Correct any deficiencies — biotin, iron, vitamin D, zinc — as these substantially affect hair quality.
Avoid with finasteride: High-dose DHT-based supplements or "testosterone boosters" claiming DHT effects make no sense on finasteride (you're suppressing DHT pharmacologically; you cannot simultaneously increase it). Competing 5α-reductase inhibitors (saw palmetto at high doses, stinging nettle extracts) provide no benefit over finasteride alone. Alcohol and finasteride are not specifically interactive but alcohol-induced hepatic stress is worth minimizing on any chronic medication.
Side Effects & Safety
Contraindications
**Absolute contraindications**: **Pregnancy** — finasteride is **Pregnancy Category X** (contraindicated) due to teratogenic risk. Finasteride crosses the placenta and produces **feminization of male fetal external genitalia** through DHT deprivation during critical developmental windows. Women who are pregnant or may become pregnant must not take finasteride and should not handle crushed or broken tablets (intact tablets are coated and safe to handle). If a partner of a man taking finasteride becomes pregnant, the low finasteride exposure from semen (<7 ng/ejaculate) is below any demonstrated teratogenic threshold and condoms are not typically mandated, though some guidelines recommend them as a precaution. **Hypersensitivity** to finasteride or its components — known allergic reaction to any 5α-reductase inhibitor. **Active liver disease** — significant hepatic impairment (Child-Pugh B-C or elevated transaminases >3× ULN) requires careful individual assessment; routine use is relatively contraindicated. **Relative contraindications requiring careful discussion**: **Pre-existing depression, anxiety, or psychiatric history** — given the association with depression and suicidal ideation in post-marketing surveillance, users with significant mood disorder history should have explicit risk-benefit discussion before initiating, close monitoring on treatment, and low threshold for discontinuation if mood symptoms emerge. Some practitioners will decline to prescribe finasteride in men with active major depressive disorder or recent suicidality. **Pre-existing sexual dysfunction** — men with baseline erectile dysfunction, low libido, or ejaculatory disorder may experience worsening on finasteride and may have difficulty distinguishing drug effect from baseline. Careful counseling and often preferential use of topical formulations are reasonable. **Planning pregnancy in the near term** — women planning pregnancy within ~1 year should not use finasteride or should discontinue with sufficient washout (4-6 weeks covers plasma clearance; semen clearance is similar). Men planning conception should be aware that finasteride does not impair fertility in most men but can affect ejaculate volume and has theoretical spermatogenesis effects at high doses. **Suspected or diagnosed prostate cancer** — finasteride suppresses PSA and can mask detection; in men with palpable prostate abnormalities or significantly elevated PSA, evaluation should precede initiation. In men with confirmed prostate cancer, finasteride is generally not used during active treatment without urologic oncologist direction. **Family history of male breast cancer** — rare but reported in finasteride users; men with strong family history should have careful breast examination at baseline and periodically. **Elderly with polypharmacy** — while finasteride has minimal drug interactions, elderly patients often have concurrent conditions (cardiovascular, renal, hepatic) that warrant complete review before adding another medication. **Situations requiring medical consultation before use**: **Any psychiatric symptoms on treatment** — new or worsened depression, anxiety, suicidal thoughts require **immediate discontinuation and psychiatric evaluation**. Do not persist through psychiatric side effects. **Breast changes** — new lumps, nipple discharge, skin changes, or persistent breast tenderness require prompt evaluation to rule out breast cancer and to assess gynecomastia severity. **Persistent sexual dysfunction** — does not resolve with brief drug holiday or dose reduction — warrants discontinuation and endocrine/urologic evaluation. **Urinary retention** (in men with BPH) — sudden inability to urinate despite finasteride use warrants emergency evaluation. **Unexpected PSA rise on treatment** — any increase in on-treatment PSA warrants urologic evaluation. **Legal and regulatory notes**: Finasteride is a **prescription medication** in essentially all countries. It is not a controlled substance and is not restricted in competitive sport (unlike DHT itself or anabolic steroids). Some military and law-enforcement entry requirements may inquire about finasteride use — disclosure is generally recommended. This is educational content only and not medical advice. Any use of finasteride for any indication warrants physician supervision, informed consent regarding the full spectrum of potential effects including post-finasteride syndrome, baseline assessment, and periodic monitoring. The decision to use or continue finasteride should involve clear-eyed assessment of individual risk tolerance, aesthetic/clinical priorities, and alternatives.
Additional Notes
Dosing:
Androgenetic alopecia: Finasteride 1mg PO daily, taken at approximately the same time each day. Food does not significantly affect absorption. Standard commercial formulations (Propecia, generic finasteride) are available as 1mg tablets. Some practitioners use 1.25mg (cutting a 5mg tablet into quarters) for perceived efficacy improvement over 1mg, but evidence for dose-response above 1mg in hair loss is limited. Duration: indefinite while efficacy and tolerance are maintained.
BPH: Finasteride 5mg PO daily, long-term. Often combined with alpha-blocker (doxazosin, tamsulosin) during the first 6-12 months for symptom relief pending finasteride's prostate-volume effect. Duration: indefinite in most cases; some urologists consider dose reduction to 1-2.5mg maintenance after significant prostate shrinkage, though this is not standard.
Topical finasteride: 0.25% solution 1mL applied BID to affected scalp areas. Allow to dry completely before combing or lying down. Wash hands after application. Some formulations combine topical finasteride with minoxidil (e.g., Minoxi+Fin); single-solution convenience may improve adherence. Currently non-FDA-approved in the US (available via compounding); approved in some EU countries.
Female pattern hair loss (post-menopausal, off-label): Finasteride 2.5mg or 5mg PO daily, with strict contraception or confirmed post-menopausal status. Lower doses (1mg) have limited efficacy in women.
Hirsutism / PCOS androgenic symptoms: Finasteride 2.5-5mg PO daily, in combination with reliable contraception. Usually combined with spironolactone and/or oral contraceptive for comprehensive androgen blockade.
Transgender feminizing HRT adjunct: Finasteride 1-5mg PO daily, depending on regimen specifics and practitioner preference. Usually alongside estradiol and antiandrogen.
Adjustments for renal/hepatic impairment: Renal impairment: no dose adjustment required for mild-moderate impairment; caution and possible dose reduction in severe impairment given reduced clearance. Hepatic impairment: dose reduction may be appropriate in moderate-severe impairment given CYP3A4-mediated metabolism; clinical judgment required.
Drug interactions affecting dosing: CYP3A4 inhibitors (ketoconazole, clarithromycin, ritonavir) may modestly increase finasteride levels but clinical significance is usually minimal. CYP3A4 inducers (rifampin, carbamazepine, phenytoin) may decrease levels. No clinically significant dose adjustment required for most common medications.
Timing and administration notes: Finasteride can be taken at any time of day. Many users prefer morning dosing to align with other medications; others prefer evening to minimize awareness of any subjective effects. Consistency in timing is more important than specific time. Missed doses: take as soon as remembered unless it's close to the next scheduled dose; do not double up. Given the irreversible enzyme inhibition mechanism, a single missed dose has minimal pharmacodynamic impact.
PSA monitoring adjustment: After 6+ months of finasteride therapy, double the measured PSA for interpretation in prostate cancer screening. Any rise from on-treatment baseline warrants urologic evaluation. Establish on-treatment PSA baseline at 6 months; monitor thereafter per standard prostate cancer screening guidelines.
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Frequently Asked Questions
What is the recommended Finasteride dosage?
Dosage for Finasteride varies by protocol. Consult a qualified healthcare provider.
How often should I take Finasteride?
Administration frequency depends on the specific protocol. Consult current research literature.
Does Finasteride need to be cycled?
Cycling requirements depend on the protocol. Follow established research guidelines.
What are Finasteride side effects?
**Finasteride's side effect profile requires honest, detailed discussion** given the unusual intersection of well-established common transient effects, rare-but-serious effects, and the disputed post-finasteride syndrome phenomenon. Trial data, post-marketing surveillance, and patient registry data each provide partial views of the full risk picture. **Common sexual side effects (RCT data)**: Across pivotal trials of finasteride 1mg/day for hair loss, sexual side effects were reported at modestly elevated rates versus placebo. **Decreased libido** occurred in ~1.8% vs 1.3% (placebo), **erectile dysfunction** in ~1.3% vs 0.7%, **ejaculation disorder** (reduced ejaculate volume, delayed ejaculation) in ~1.2% vs 0.7%. At 5mg/day for BPH, rates are approximately 2-3× higher: decreased libido ~6% vs 3%, erectile dysfunction ~8% vs 4%, ejaculation disorder ~4% vs 1%. Most trial-reported sexual side effects **reversed with drug discontinuation in the trial follow-up period** (typically days to weeks), and many resolved with continued dosing (tolerance development). These trial-reported rates may underestimate real-world sexual side effects for several reasons: trial subjects were generally younger and healthier than real-world users; subjects with baseline sexual dysfunction were often excluded; and spontaneous reporting without specific prompting tends to underestimate subjective symptoms. Real-world surveys and patient-reported outcome studies have documented sexual side effects in 5-15% of finasteride users at various time points. **Post-finasteride syndrome (PFS) — the persistent variant**: Distinct from the transient sexual side effects that resolve with discontinuation, a subset of users report **persistent** sexual, neurologic, and psychological symptoms lasting months to years after stopping finasteride. Documented PFS-associated symptoms include: **persistent loss of libido**, **persistent erectile dysfunction**, **loss of morning erections**, **genital sensory changes** (numbness, reduced tactile sensitivity), **penile shrinkage** or shape changes, **low mood, depression, anxiety, panic**, **cognitive symptoms** (brain fog, memory difficulties, emotional blunting), **sleep disturbance**, **muscle weakness or atrophy**, and **somatic symptoms** (body composition changes, temperature dysregulation). The **FDA updated Propecia labeling in April 2012** to include warnings about persistent sexual dysfunction, and subsequent updates added depression and suicidal ideation warnings. Europe, Canada, UK, and Australia have made parallel regulatory changes. Epidemiology is debated: PFS is clearly real in case series and registry data (**Foundation for Post-Finasteride Syndrome** patient registry has documented thousands of cases), but incidence estimates vary widely (<1% to 2-3% of users) and no prospective RCT has been specifically designed to quantify PFS rates. Individual susceptibility likely involves genetic variation in steroidogenic enzymes, age at initiation, duration of use, pre-existing mood/anxiety profile, and other factors that remain incompletely characterized. Mechanistic hypothesis involves persistent neurosteroid dysregulation (documented in **Melcangi et al.** studies), possibly with epigenetic or receptor-adaptation changes that don't fully resolve on discontinuation. **Suicidal ideation and depression**: Finasteride has been associated with **depression and suicidal ideation** in post-marketing surveillance, leading to FDA labeling updates including boxed warnings in some jurisdictions. **Irwig 2012** documented depression and suicidal thoughts in a subset of PFS-affected men. Population-level pharmacoepidemiology studies (**Welk et al. 2017** *JAMA Intern Med*) found modestly elevated suicide risk in older men initiating finasteride. Anyone with baseline depression, bipolar disorder, or suicidal history should have careful risk-benefit discussion before initiating; all users should be educated about mood-symptom warning signs and have a plan for prompt discontinuation and psychiatric evaluation if these occur. **Gynecomastia and breast changes**: Finasteride modestly increases serum estradiol (via reduced 5α-reduction of testosterone, leaving more T for aromatization). This produces **breast tenderness, swelling, or gynecomastia** in ~1-2% of users at 1mg/day and higher rates at 5mg/day (~2-4%). Gynecomastia is usually modest and often reverses with discontinuation but can become fibrotic and persistent with prolonged exposure, requiring surgical correction. **Male breast cancer** reports in finasteride users have appeared in case series and post-marketing data, though a definitive causal link remains unproven; pharmacoepidemiology is mixed. Any new breast lump, nipple discharge, or skin changes in a man on finasteride warrants immediate evaluation. **PSA effects and prostate cancer screening**: Finasteride suppresses serum PSA by approximately **50%**, which must be accounted for in prostate cancer screening. Standard practice is to **multiply the measured PSA by 2** for interpretation after ≥6 months of finasteride treatment, using the doubled value for screening algorithms. Any rise in PSA on finasteride (measured PSA increasing over baseline on-treatment level) is concerning and warrants urologic evaluation. This PSA suppression effect was a source of the initial Gleason score concern in the PCPT trial and is a real practical consideration for men using finasteride. **Prostate cancer risk — contested**: As discussed in clinical studies, the PCPT controversy around high-grade prostate cancer has largely been resolved in favor of finasteride's overall safety, but some practitioners remain cautious about recommending finasteride for younger men with family history of aggressive prostate cancer. This should be individually discussed. **Teratogenic risk — pregnancy-category X**: Finasteride causes **feminization of male fetal genitalia** through DHT deprivation during critical fetal developmental windows. Pregnant women should not handle crushed or broken tablets (intact tablets are coated and safe to handle). Women of reproductive potential should avoid finasteride altogether; if prescribed for post-menopausal hair loss, strict contraception should be ensured until menopause is definitively established. Semen exposure: finasteride is present in semen at low concentrations (<7 ng per ejaculate), and the theoretical exposure to a pregnant partner is below any demonstrated teratogenic threshold — condoms are not typically required for men taking finasteride with pregnant partners, though some guidelines recommend them as a precaution. **Hepatic and other effects**: **Hepatic effects** are uncommon but finasteride is CYP3A4-metabolized, and rare hepatotoxicity has been reported. **Allergic reactions** (rash, urticaria, angioedema) occur rarely. **Testicular pain** and orchialgia have been reported in post-marketing surveillance. **Depression-like cognitive symptoms** including reduced emotional range and concentration are commonly reported qualitatively even when not meeting clinical depression criteria. **Drug interactions**: Finasteride is minimally interactive in clinical practice. CYP3A4 is the primary metabolizing enzyme, but inhibition or induction rarely produces clinically significant finasteride level changes. No major interactions with most common medications have been established. Concomitant use with alpha-blockers (doxazosin, tamsulosin) for BPH is common and well-tolerated. Concomitant use with minoxidil for hair loss is standard and synergistic. Concomitant use with testosterone therapy (TRT) is possible but reduces the bodily DHT response to T normalization — some practitioners prefer to treat TRT patients without 5AR inhibitors to preserve normal DHT biology, while others continue finasteride for hair preservation during TRT.
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