What Is Finasteride Used For? Hair Loss and Enlarged Prostate Explained
Finasteride blocks the conversion of testosterone to DHT, the androgen that shrinks scalp hair follicles and enlarges the prostate. Taken once a day, it can slow male pattern baldness or ease urinary symptoms from benign prostatic hyperplasia (BPH).
Finasteride is a prescription 5-alpha-reductase (5-AR) inhibitor that treats two common male conditions: androgenetic alopecia (male pattern hair loss) at a 1 mg dose and benign prostatic hyperplasia (BPH) at a 5 mg dose. By lowering dihydrotestosterone (DHT) levels, it helps regrow or preserve scalp hair and shrinks an enlarged prostate, improving urine flow and reducing the risk of acute urinary retention. Women who are or may become pregnant must never handle crushed tablets because finasteride can harm a male fetus.
- Finasteride 1 mg daily (brand Propecia) increased scalp hair counts by an average of 17 hairs in a 1 cm² area at 48 weeks while placebo led to a loss of 10 hairs (dailymed.nlm.nih.gov).
- Finasteride 5 mg daily (brand Proscar) improved BPH symptom scores by −2.3 points versus −1.6 with placebo after one year (dailymed.nlm.nih.gov).
- Common sexual side effects in the first year include decreased libido (1.8 % vs 1.3 % with placebo) and erectile dysfunction (1.3 % vs 0.7 %) (dailymed.nlm.nih.gov).
- DHT levels fall by about 70 % within 24 hours of the first dose, but noticeable hair or prostate benefits usually take at least three to six months (dailymed.nlm.nih.gov).
- Finasteride is contraindicated in pregnancy, and women should not handle broken tablets because transdermal absorption could harm a developing male fetus (dailymed.nlm.nih.gov).
Finasteride at a glance
Finasteride is a type II 5-AR inhibitor that lowers circulating and scalp levels of dihydrotestosterone (DHT) by about 60-70 %. DHT is the androgen responsible for shrinking hair follicles in androgenetic alopecia and stimulating prostate tissue growth in BPH.
The drug comes as a finasteride 1 mg tablet for hair loss and a 5 mg tablet for prostate enlargement. Both strengths are taken orally once daily and can be swallowed with or without food. Brand names include Propecia (1 mg) and Proscar (5 mg).
Finasteride received its first FDA approval in 1992 for BPH and in 1997 for male pattern hair loss.
How finasteride lowers DHT
The enzyme 5-alpha-reductase converts testosterone into the more potent androgen DHT. Finasteride selectively blocks the type II isoform of this enzyme found in hair follicles and prostate tissue, causing a rapid drop in tissue DHT concentrations. Reduced DHT slows follicle miniaturization in the scalp and shrinks enlarged prostate tissue, easing bladder outlet obstruction. Serum testosterone rises slightly within the normal range.
FDA-approved and off-label uses
Finasteride has two FDA-approved indications and several emerging off-label uses.
Approved indications:- Male pattern hair loss (androgenetic alopecia): 1 mg once daily in men 18-41 years (dailymed.nlm.nih.gov).
- Benign prostatic hyperplasia: 5 mg once daily in men ≥45 years with symptomatic enlarged prostates (dailymed.nlm.nih.gov).
- Adjunct to hormonal therapy in transgender women to reduce scalp hair loss
- Treatment of female pattern hair loss in post-menopausal women (efficacy not demonstrated in trials (dailymed.nlm.nih.gov))
- Prevention of prostate cancer progression (not recommended; higher rates of high-grade tumors in trials)
Clinicians may also prescribe dutasteride, a dual 5-AR inhibitor, or combine finasteride with minoxidil for hair regrowth when appropriate.
| Use | Daily Dose | Typical Age Range | Earliest Expected Benefit |
|---|---|---|---|
| Male pattern hair loss | 1 mg | 18-41 years | 3 months (dailymed.nlm.nih.gov) |
| Benign prostatic hyperplasia | 5 mg | ≥45 years | 6 months (dailymed.nlm.nih.gov) |
How well does finasteride work?
Clinical trials show clinically meaningful improvements in both hair density and BPH symptom scores.
Hair regrowth:In a 48-week vertex-scalp study, men taking 1 mg finasteride gained a mean of 7 terminal hairs and 18 anagen hairs per 1 cm², while placebo recipients lost 10 hairs and 9 anagen hairs (dailymed.nlm.nih.gov). Visible improvement was noted by month 3 and maintained for at least five years (dailymed.nlm.nih.gov).
BPH symptom relief:The PROSCAR Long-Term Efficacy and Safety Study (PLESS) found a 2.3-point drop in American Urological Association (AUA) symptom score at one year versus 1.6 with placebo; benefits persisted through four years (dailymed.nlm.nih.gov). Maximum urine flow increased by 1.0 mL/s at month 4 compared with 0.3 mL/s on placebo (dailymed.nlm.nih.gov).
| Adverse experience (Year 1) | Finasteride 1 mg (%) | Placebo (%) |
|---|---|---|
| Decreased libido | 1.8 | 1.3 |
| Erectile dysfunction | 1.3 | 0.7 |
| Ejaculation disorder | 1.2 | 0.7 |
Possible side effects and risks
Finasteride is generally well tolerated, but sexual side effects and prostate-specific antigen (PSA) changes warrant discussion.
Sexual function: Decreased libido, erectile dysfunction, or reduced ejaculate volume occurred in 1-2 % of men during the first year; incidence fell to ≤0.3 % by year 5 (dailymed.nlm.nih.gov). Most cases resolved with continued therapy or after stopping the drug.Breast changes: Rare tenderness or enlargement were reported (<2 %) (dailymed.nlm.nih.gov).
High-grade prostate cancer: Finasteride 5 mg was associated with a higher rate of Gleason 8-10 tumors (1.8 % vs 1.1 %) in the Prostate Cancer Prevention Trial (dailymed.nlm.nih.gov). The clinical significance remains uncertain, so shared decision-making is key.
Depression and anxiety: Post-marketing cases exist, though causality is unclear; monitor mood changes.
PSA suppression: Finasteride lowers PSA by about 50 %. Tell your doctor before any PSA test so results can be interpreted correctly (dailymed.nlm.nih.gov).
⚠️ Tablet handling safety for women
Pregnant women should not handle broken or crushed finasteride tablets. If contact occurs, wash the area with soap and water immediately (dailymed.nlm.nih.gov).
Who should not take finasteride?
Finasteride is contraindicated in certain situations.
- Women who are or may become pregnant (risk to male fetus)
- Children and adolescents (no proven benefit; safety not established)
- Anyone with hypersensitivity to finasteride or tablet excipients
- Men undergoing PSA screening who cannot have results adjusted
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How to start finasteride treatment online
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Is finasteride the right first step for you?
Check the column that fits your situation:
✅ Likely a good fit
- Male pattern hair loss diagnosed by a clinician
- BPH with prostate volume >30 mL on imaging
- No plans for children in the next year
- Comfortable with once-daily tablets and routine lab follow-up
🏥 See a doctor in person
- Sudden patchy hair loss or scalp scarring
- Blood in urine, severe urinary pain, or fever
- Breast lumps, nipple discharge, or unexplained weight loss
- History of liver disease or abnormal liver tests
- Depression, low mood, or anxiety that is worsening
🚨 When to Contact Your Healthcare Provider
Contact your doctor immediately if you experience any of the following:
- Breast tenderness, swelling, or nipple discharge: could signal rare male breast cancer.
- Palpable breast lump: needs prompt evaluation.
- Persistent erectile dysfunction or loss of libido: may warrant dose adjustment or discontinuation.
- Severe depression or suicidal thoughts: stop the drug and call 988 or get emergency help.
- Hematuria (blood in urine): may indicate prostate or bladder issue.
- Urinary retention: inability to pass urine requires emergency care.
- Skin rash or swelling of lips/face: signs of allergic reaction.
- Any rapid change in PSA levels: could mask prostate cancer.
When to see a doctor
If you are unsure whether your symptoms fit routine hair loss or BPH, schedule an in-person evaluation. Sudden hair shedding, painful urination, or systemic symptoms like fever and weight loss should never be self-treated.
Scientific References
- These highlights do not include all the information needed to use PROPECIA safely and effectively. See full prescribing information for PROPECIA. PROPECIA® (finasteride) tablets for oral use Initial U.S. Approval: 1992. dailymed.nlm.nih.gov.
- DailyMed: PROSCAR- finasteride tablet, film coated. dailymed.nlm.nih.gov.
Frequently Asked Questions
How long does finasteride stay in your system?
Finasteride’s plasma half-life is about 6 hours in adults under 60 and 8 hours in older men, but its DHT-lowering effect lasts roughly 24 hours. Missing an occasional dose is unlikely to reverse benefits, yet consistent daily dosing is needed for sustained results.
Can I combine finasteride with minoxidil for better hair regrowth?
Yes. Finasteride and topical or oral minoxidil work through different mechanisms and are often combined for additive benefits, especially when monotherapy plateaus. Your provider can advise on timing and monitoring.
Does finasteride lower testosterone?
No. Finasteride blocks conversion of testosterone to DHT, so total testosterone may rise slightly within the normal range. It does not suppress testosterone production.
Will side effects go away if I stop taking finasteride?
Most sexual side effects resolve after discontinuation, and many improve even during ongoing therapy. Rare persistent cases have been reported, so discuss risks before starting.
Is generic finasteride as effective as brand Propecia or Proscar?
Yes. FDA-approved generics must demonstrate bioequivalence, delivering the same active ingredient and clinical effect at a lower cost.
Can women use finasteride for hair loss?
Finasteride is not FDA-approved for women, and a 12-month trial in post-menopausal women showed no benefit over placebo (dailymed.nlm.nih.gov). Pre-menopausal women must avoid it due to fetal risk.
What happens to my hair if I stop finasteride?
Benefits gradually reverse over about 12 months, and hair counts return to baseline as DHT levels rebound (dailymed.nlm.nih.gov). Continuing therapy is needed to maintain gains.
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