Finasteride for Hair Loss: The Complete Guide

Finasteride is the only FDA-approved oral medication for male pattern hair loss. First approved in 1997 under the brand name Propecia, it's now available as an inexpensive generic that costs a few dollars per month. For most men losing their hair, it's the single most effective treatment available.

But effectiveness comes with caveats. It requires daily use for as long as you want to keep your hair, it doesn't work for everyone, and a small percentage of men experience side effects. Here's what the research actually shows.

How Finasteride Works

Male pattern baldness (androgenetic alopecia) is caused by sensitivity to dihydrotestosterone, or DHT. This hormone binds to receptors in hair follicles, causing them to shrink and produce progressively thinner, shorter hairs until they eventually stop producing visible hair altogether.

Finasteride works by blocking the enzyme (type II 5-alpha reductase) that converts testosterone into DHT. At the standard 1mg daily dose, it reduces scalp DHT levels by about 60-70%. With less DHT attacking your follicles, the miniaturization process slows or stops, and in many cases, hair follicles recover and produce thicker hair again.

This is what makes finasteride unique—it addresses the underlying cause of hair loss rather than just stimulating growth like minoxidil does.

What Results to Expect

Clinical trials involving thousands of men have established clear expectations for finasteride results.

The Numbers

In the original clinical trials, 86% of men taking finasteride stopped or slowed their hair loss, and 65% experienced visible regrowth. After two years, 83% of men on finasteride showed no further hair loss compared to baseline, versus only 28% on placebo. Global photographs showed hair growth improvement in 48% at one year and 66% at two years.

It's important to understand that finasteride primarily stops further loss. Regrowth is a bonus that many experience, but the main value is preserving the hair you still have. This is why starting earlier typically produces better outcomes—there's more hair left to save.

Side Effects: What the Research Shows

Side effects are the main concern people have about finasteride. Here's what clinical trials and research actually demonstrate.

Sexual Side Effects

In the original trials, 3.8% of men on finasteride reported sexual side effects compared to 2.1% on placebo—a difference of about 1.7%. These include decreased libido, erectile dysfunction, and reduced ejaculate volume. Importantly, in most men who experienced these effects, they either resolved while continuing treatment or quickly after stopping.

Post-Finasteride Syndrome

Some users report persistent side effects after discontinuing finasteride—a controversial condition called "post-finasteride syndrome." While real to those experiencing it, the condition is not well-understood, lacks standardized diagnostic criteria, and research has not conclusively established causation versus correlation. The actual incidence appears to be rare, but it's something to be aware of.

Oral vs Topical Finasteride

Oral finasteride (the pill) is FDA-approved and has decades of research behind it. Topical finasteride—applied directly to the scalp—is newer but increasingly popular.

A 2022 Phase 3 clinical trial found topical finasteride (0.25% solution) was as effective as oral finasteride for hair regrowth. The key difference: topical formulations had nearly 2% fewer reported sexual side effects, likely because less of the drug enters systemic circulation.

Topical finasteride is available through compounding pharmacies and some telehealth platforms, though it's not FDA-approved specifically. It's a reasonable option for men concerned about systemic side effects.

Who Should (and Shouldn't) Take Finasteride

Good Candidates

Men with male pattern baldness (the typical receding hairline and crown thinning pattern), those who want to preserve existing hair (earlier is better), men who have tried minoxidil alone with limited success, and those comfortable with daily medication.

Not Appropriate For

Women who are pregnant or may become pregnant (finasteride can cause birth defects in male fetuses), men whose hair loss is caused by something other than androgenetic alopecia (like alopecia areata, telogen effluvium, or scarring alopecia), and those with a history of severe reactions to 5-alpha reductase inhibitors.

Combining with Minoxidil

Finasteride and minoxidil work through completely different mechanisms—finasteride blocks DHT while minoxidil stimulates blood flow and extends the growth phase. Using both together often produces better results than either alone.

Research confirms this synergy. A systematic review found that the combination of finasteride and topical minoxidil was more effective than either treatment alone for increasing hair count and improving appearance.

How to Get Finasteride

Finasteride requires a prescription. You have several options for obtaining it.

What Happens If You Stop?

Finasteride's effects only last as long as you take it. If you stop, DHT levels return to normal within weeks, and the hair loss process resumes. Most men lose the gains they made within 6-12 months of stopping. This is why finasteride is typically a long-term commitment.

The Bottom Line

Finasteride is the most effective treatment available for male pattern hair loss. It works by addressing the root cause—DHT sensitivity—rather than just masking symptoms. The research is clear: most men who take it will stop or slow their hair loss, and a majority will experience some regrowth.

The decision to use finasteride involves weighing proven benefits against a small risk of side effects. For most men concerned about hair loss, the math works out in favor of treatment—especially when starting early, while there's more hair to preserve.

If side effects are a concern, topical finasteride or combining lower-dose finasteride with minoxidil are options worth discussing with a healthcare provider.