✓ Medically reviewed by · Last reviewed: May 2026
Pharmacy Researcher · 8 years experience
Pharmacy researcher with 8 years reviewing clinical drug information, generic formulation equivalence, and international pharmaceutical standards. Focuses on patient-facing accuracy in medication education.
Reviewed by Sophie Carter, MPharm — last reviewed 11 May 2026
Quick Answer — Finasteride 1mg vs 5mg
Finasteride 1 mg (brand: Propecia, generic: Finpecia) is the approved dose for male pattern hair loss. Finasteride 5 mg (brand: Proscar, generic: Proscar) is the approved dose for benign prostatic hyperplasia (BPH). Both doses reduce scalp DHT by 60–70%. The 5 mg dose does not meaningfully outperform 1 mg for hair loss — it just adds cost and side-effect risk with no clinical advantage for androgenetic alopecia.
Why two doses exist
Finasteride was first approved in 1992 at 5 mg for BPH (Proscar). In 1997, Merck trialled it at lower doses and found that 1 mg produced equivalent scalp DHT suppression for hair loss purposes. The FDA approved finasteride 1 mg (Propecia) for androgenetic alopecia in 1997. Since then, both doses exist — 5 mg for prostate, 1 mg for hair.
The key pharmacological point: finasteride’s dose-response curve for DHT suppression is steep at low concentrations and flattens early. Most of the DHT-lowering effect is achieved by 0.2 mg; the difference between 1 mg and 5 mg in scalp DHT suppression is modest (60–70% vs 70–75%), while systemic DHT suppression is substantially higher at 5 mg, which drives the different side-effect exposure.
DHT suppression comparison
| Metric | 1 mg | 5 mg |
|---|---|---|
| Serum DHT reduction | ~70% | ~85% |
| Scalp DHT reduction | ~60–70% | ~70–75% |
| Hair loss efficacy (AGA) | Well-established (FDA-approved indication) | Not significantly superior in head-to-head trials |
| Systemic DHT suppression | Lower | Higher — drives more side-effect risk |
Research Spotlight
A 2002 Merck-sponsored trial directly comparing 1 mg and 5 mg finasteride in 424 men with AGA found no statistically significant difference in hair count improvement at 48 weeks. The 1 mg dose was associated with equivalent efficacy and a trend toward fewer sexual side effects. Most subsequent hair-loss trials use 1 mg as standard.
Side effects — where the doses differ
Finasteride’s side effects are driven by systemic DHT suppression. Because 5 mg suppresses serum DHT more aggressively than 1 mg, the risk is proportionally higher at 5 mg:
- Sexual side effects (decreased libido, erectile dysfunction, reduced ejaculation volume): ~2–4% at 1 mg in clinical trials; reported higher in real-world post-marketing data. At 5 mg, absolute risk is higher due to greater DHT suppression.
- Post-finasteride syndrome: a contested but documented cluster of persistent sexual and neurological symptoms after discontinuation. Most robust signal at higher doses in observational literature.
- PSA reduction: finasteride halves PSA levels. Anyone being screened for prostate cancer must tell their doctor they are on finasteride — normal range PSA must be doubled to interpret correctly.
- Pregnancy: finasteride is teratogenic in male foetuses. Women who are or could be pregnant must not handle crushed or broken tablets. Not a concern for the male user himself.
Which dose for hair loss?
Always 1 mg. There is no clinical evidence that 5 mg produces better hair outcomes than 1 mg for androgenetic alopecia. The 5 mg dose adds systemic DHT suppression without proportionally adding scalp benefit, while meaningfully increasing exposure to side effects.
Some men use finasteride 5 mg tablets and quarter them (effectively ~1.25 mg) as a cost-reduction strategy — the pill-splitting approach gives approximately equivalent DHT suppression to branded 1 mg tablets at a fraction of the price. This is a widely used off-label approach. Tablet-splitting finasteride is pharmacologically reasonable (it is not a sustained-release or enteric-coated formulation) but is not approved practice.
Products: Finpecia 1 mg (Cipla, WHO-GMP) is the standard generic. Proscar 5 mg (MSD) is available for BPH or cost-splitting use.
How long until results?
- 3 months: hair shedding often increases initially (miniaturised hairs shedding to make way for terminal hairs). This is alarming but expected.
- 6 months: shedding stabilises. Some users see early regrowth in the crown.
- 12 months: peak hair count improvement in most responders. ~66% of users see regrowth; ~30% see stabilisation; ~5% see continued loss.
- Ongoing: benefits persist only with continued use. Stopping finasteride leads to return of DHT-driven miniaturisation within 6–12 months.
Finasteride vs dutasteride — is there a stronger option?
Dutasteride inhibits both Type I and Type II 5-alpha-reductase (finasteride only inhibits Type II), suppressing serum DHT by ~95% vs ~70% for finasteride. It outperforms finasteride in some head-to-head hair trials but with a substantially higher side-effect burden and much longer washout period (~5 months vs 1–2 weeks for finasteride). For a full comparison, see our finasteride vs dutasteride guide.
Combining with minoxidil
Finasteride and minoxidil act through completely independent mechanisms — finasteride blocks DHT production; minoxidil prolongs the anagen (growth) phase and increases follicular blood supply. Combination therapy consistently outperforms either agent alone in clinical trials. See our minoxidil vs finasteride comparison for the full evidence.
Medical Disclaimer
This article is for informational purposes. Finasteride is a prescription medicine in many countries. Do not use if you are a woman of childbearing potential. Discuss side-effect risk with a doctor or pharmacist before starting.
Written by
Sophie ChenPharmaceutical Content Researcher · 8 years experience
Sophie Chen is a pharmaceutical content researcher with 8 years covering generic medication access and clinical pharmacology. She specialises in international regulatory frameworks, bioequivalence standards, and patient-facing education on therapeutic drug classes. She is not a clinician.