From the FDA Drug Label
The development and enlargement of the prostate gland is dependent on the potent androgen, 5α -dihydrotestosterone (DHT). Type II 5α-reductase metabolizes testosterone to DHT in the prostate gland, liver and skin. Finasteride is a competitive and specific inhibitor of Type II 5α-reductase with which it slowly forms a stable enzyme complex.
The FDA drug label does not answer the question about finasteride hair loss.
From the Research
Finasteride is a highly effective medication for treating male pattern hair loss, and the recommended dose is 1mg taken orally once daily, with results typically appearing after 3-6 months of consistent use and maximum benefits seen after about 1-2 years. The most recent and highest quality study, published in 2025 1, demonstrates the effectiveness of combined oral minoxidil and finasteride in male androgenetic alopecia, with 92.4% of patients achieving stable or improved outcomes and 57.4% showing marked improvements. Finasteride works by inhibiting the enzyme 5-alpha reductase, which converts testosterone to dihydrotestosterone (DHT), a hormone that shrinks hair follicles in genetically susceptible men. By reducing DHT levels, finasteride helps maintain existing hair and can promote new growth.
Some key points to consider when using finasteride for hair loss include:
- The medication is generally well-tolerated, but side effects may include decreased libido, erectile dysfunction, and decreased ejaculate volume in a small percentage of users (around 2-3%) 2, 3.
- These effects are usually reversible upon discontinuation, but patients should be educated about the possible short- and long-term side effects 3.
- Women who are pregnant or may become pregnant should not handle crushed tablets due to potential risks to male fetuses 2.
- For optimal results, finasteride is often combined with minoxidil (topical solution or foam), and treatment must be continued long-term as hair loss will resume if the medication is stopped 4, 1.
- The combined oral minoxidil-finasteride regimen has been shown to produce statistically significant and clinically meaningful improvements in male pattern hair loss, with substantial proportions of stable or improved patients and large effect sizes in severe stages 1.