Finasteride Dosage UK

Finasteride Dosage UK — 1 mg & 5 mg Guide

Posology based on the MHRA-approved Summary of Product Characteristics (SmPC) for Propecia (1 mg) and Proscar (5 mg). | Back to UK hub

MHRA-approved dosing

Indication	Brand (UK)	MHRA-approved dose	Route	Frequency
Androgenetic alopecia (AGA)	Propecia / generic 1 mg	1 mg	Oral	Once daily
Benign prostatic hyperplasia (BPH)	Proscar / generic 5 mg	5 mg	Oral	Once daily

Source: MHRA-approved SmPCs for Propecia and Proscar (eMC, 2024). No dose adjustment required for renal impairment. Dose reduction not required in elderly patients.

Finasteride 1 mg — hair loss (AGA)

Dose: 1 mg by mouth, once daily
With or without food: Either; food does not affect bioavailability
Best time: No evidence for a specific time of day; consistency is more important than timing. See time of day guide.
Duration: Indefinite — hair loss returns to pre-treatment baseline within 6–12 months of stopping
Minimum trial period: 6–12 months before assessing response per NICE CKS and MHRA SmPC

Finasteride 5 mg — BPH

Dose: 5 mg by mouth, once daily
NHS prescribable: Yes — on FP10; NICE NG145 endorsed for men with enlarged prostate (≥30 mL or PSA ≥1.4 ng/mL)
Expected response: Maximum prostate volume reduction (20–30%) at 6–12 months; symptom improvement (IPSS) typically evident at 3–6 months
Combination with alpha-blocker: NICE NG145 recommends combination therapy (finasteride + alpha-blocker) for men with moderate-to-severe LUTS and enlarged prostate

Missed dose

The MHRA SmPC does not provide explicit missed-dose guidance. Based on finasteride’s pharmacokinetics (half-life 5–6 hours; DHT suppression maintained for days): if you miss a dose, take it as soon as you remember on the same day. If you only remember the next day, skip the missed dose and resume normal dosing. Do not take a double dose.

Special populations (MHRA contraindications)

Population	MHRA guidance
Women — pregnant or of childbearing potential	Contraindicated. Finasteride may cause abnormalities of the external genitalia of a male foetus. Women must not handle crushed tablets.
Children / adolescents under 18	Not licensed. No data.
Renal impairment	No dose adjustment required.
Hepatic impairment	Use with caution — no data for severe hepatic impairment. Not recommended if significantly impaired liver function.
Elderly (>70 years)	No dose adjustment required; pharmacokinetics not significantly altered.

Source: MHRA-approved Propecia and Proscar SmPCs (eMC, 2024).

PSA monitoring note for UK prescribers

Clinical note for UK GPs and urologists: Finasteride 5 mg reduces serum PSA by approximately 50% after 6 months of use. Any measured PSA in a patient on finasteride should be multiplied by 2.0 (for 5 mg) or 1.7 (for 1 mg) to derive the equivalent untreated PSA. Do not instruct patients to stop finasteride before PSA testing — the correction formula is more reliable. Source: BAUS guidance; MHRA Proscar SmPC.

Sources: MHRA Propecia SmPC (eMC, 2024). MHRA Proscar SmPC (eMC, 2024). NICE NG145: Lower urinary tract symptoms in men (2023). Kaufman KD et al. JAAD 1998.