Finasteride Every Other Day: Does It Work?
Medically reviewed by [Reviewer Name, MD] | Last reviewed: August 2026 | Editorial policy
Bottom line: Finasteride’s long half-life means every-other-day (EOD) dosing maintains substantial DHT suppression. Limited clinical data suggest EOD dosing produces hair retention outcomes similar to daily dosing, though no large RCT has directly compared them. The approved regimen remains 1 mg daily.
Pharmacokinetic Rationale
Finasteride has an elimination half-life of approximately 5–6 hours in younger men and 6–8 hours in men over 70. However, its biological effect on Type II 5-alpha-reductase (the enzyme targeted in hair follicles and the prostate) outlasts the drug’s plasma half-life considerably. The enzyme-bound complex is the active form, and recovery of 5-AR activity after finasteride clearance takes considerably longer than the plasma half-life suggests.
| Parameter | Value |
|---|---|
| Plasma half-life | 5–6 hours (younger men); 6–8 hours (over 70) |
| DHT suppression at 24 h after 1 mg dose | ~60–70% |
| DHT suppression with EOD dosing (observed) | ~50–60% (estimated from pharmacokinetic modeling) |
| Approved dosing | 1 mg once daily |
What the Evidence Shows
A 2009 study by Shapiro et al. and subsequent retrospective analyses suggest that some men use EOD or even less-frequent dosing without apparent loss of efficacy compared to their prior daily dosing. These observations are limited by small sample sizes and lack of randomization. A 2024 systematic review did not find controlled RCT evidence directly comparing daily vs. EOD dosing.
Why Someone Might Use EOD Dosing
- Managing side effects: some men report improvement in sexual side effects with EOD while maintaining hair benefit (anecdotal; not confirmed in RCTs)
- Cost reduction (marginal — generic finasteride is already inexpensive)
- Dose-tapering attempt (discuss with your prescribing physician before altering dose)
Important: Do not alter your prescribed dosing regimen without discussing it with your provider. The evidence for EOD dosing is not sufficient to recommend it as a standard approach.
See: Finasteride dosage overview | 1 mg dosing guide | What to do if you miss a dose | Side effects