What Is Finasteride?
Finasteride is a medication that helps slow, stop, and even improve hair loss in men and women with androgenetic alopecia (pattern hair loss). It works by lowering a hormone called DHT (dihydrotestosterone), which is one of the main causes of male and female pattern baldness. Too much DHT activity can shrink susceptible hair follicles, making hair thinner over time, but by blocking this hormone, finasteride helps protect hair and encourages regrowth.
Finasteride can be taken in two main ways: as a pill that is ingested (oral finasteride) or as a liquid or spray that is applied directly to the scalp (topical finasteride). Both versions work toward the same goal of reducing DHT levels, but they have a few key differences.
Here is how they compare in terms of effectiveness, side effects, and who might benefit most from each.
How Finasteride Works
Finasteride blocks an enzyme called 5-alpha reductase, which turns testosterone into DHT. By inhibiting that conversion, less DHT builds up in your scalp. With lower DHT levels, the hair follicles stay healthier and can keep growing.
Oral finasteride affects DHT throughout your entire body, while topical finasteride mostly targets DHT in the scalp. This difference matters when it comes to both results and side effects.
Oral Finasteride
Oral finasteride dosed at 1mg daily (also known as Propecia) has been approved by the FDA since 1997 to treat male pattern baldness. It is one of the most researched hair loss treatments available and has helped millions of men slow or even reverse hair loss. Although FDA approved for men, years of experience and data have shown that women benefit from DHT-blocking agents like finasteride as well.
Studies show that taking 1 mg of oral finasteride daily can increase hair counts, especially on the crown and top of the head. Many men notice thicker hair after about three to six months, with maximal results assessed after about two years of consistent use.
Because the pill lowers DHT directly in the hair follicles and in the bloodstream, it is very effective, but this also means some people experience unwanted side effects.
Topical Finasteride
Topical finasteride is another way to use the same medication, but instead of taking it by mouth, you apply it directly to your scalp as a spray, liquid, or gel.
In early clinical studies, topical finasteride, specifically the 0.25% solution used once daily, showed similar hair growth results to the oral pill. It was found that men using topical finasteride grew about 20 new hairs per square centimeter after 24 weeks, which was nearly the same as those taking the medication by mouth.
One difference between the topical and oral forms of finasteride is how much of the medication enters the bloodstream. With topical finasteride, less of the drug was identified in the plasma. Researchers, in turn, found that topical finasteride led to a smaller drop in overall DHT levels, which likely corresponds to the lower observed rate of certain side effects.
However, it is important to note that topical finasteride is not yet FDA approved in the United States. It is made by compounding pharmacies and frequently promoted through telehealth services, which means quality and concentration, and therefore results, can vary.
Comparing Effectiveness Between Topical and Oral Finasteride
When it comes to results, both topical and oral finasteride have proven to help regrow hair and slow down hair loss. Oral finasteride works throughout the body and lowers DHT levels by about 55 to 60 percent. That broad effect leads to strong improvement in scalp hair, but can also increase the chance of side effects.
Topical finasteride focuses its action on the scalp. It usually reduces DHT in the blood by about 30 to 35 percent while still providing noticeable hair growth improvement though, in our doctors’ experience, not as much as the pill. While less of a DHT reduction, it is interesting to note that effective topical formulations of finasteride do seem to be absorbed to some extent; thus, advertising these products as eliminating the risk of adverse effects may not completely fair.
Both forms require consistent, long-term use. If you stop taking or applying finasteride, hair loss typically returns within several months. With continued use, many men start to see results in three to six months, with the most improvement around one to two years of therapy.
Side Effects and Safety
Oral Finasteride
Because the oral pill affects hormone levels, it can cause more general side effects in some men. These may include:
- Lower sex drive or erectile problems
- Changes in mood, such as anxiety or depression
- Lower PSA levels, which can affect prostate cancer screenings
Most men tolerate oral finasteride well, and side effects often improve over time or after stopping the medication. Still, it is something to discuss with a doctor in the context of your personal risk factors and treatment goals before starting the medication. Original clinical trials showed approximately 3% risk of sexual side effects, which is the concern that most of our male patients are most worried about. This means that 97% of men did not have these side effects, so the drug is considered very safe.
Topical Finasteride
Topical versions may reduce the risk of whole-body side effects since less of the drug enters the bloodstream. The most common reactions are mild skin irritation or itching where it is applied.
In 2025, the FDA issued a warning about compounded topical finasteride products after some people reported side effects such as sexual problems, depression, or “brain fog.” While these reports were rare, it is a reminder that even topical versions can have systemic effects and should only be used under medical supervision.
Who Should Consider Which?
Oral finasteride may be best for men who want the most proven and consistent results, prefer the simplicity of taking a daily pill, and are not preoccupied with side effects. It is also less expensive.
Topical finasteride might be a better choice for men who have experienced side effects from oral finasteride before, want to reduce systemic exposure, or are comfortable using an off-label treatment that is not FDA approved and are willing to apply a medication to their scalp every day.
Both forms can (and some would argue should) also be used along with minoxidil, another hair growth treatment, for stronger results. Combining the two can help boost density and slow shedding more effectively than using either one alone.
For Hair Transplant Patients
Finasteride, whether oral or topical, can also play an important role after a hair transplant. It does not affect the transplanted hairs (since they are usually DHT-resistant), but it helps protect the surrounding natural hair, keeping your overall look fuller and more even.
Surgeons often recommend continuing finasteride before and after surgery to maintain existing hair and support better long-term results.
Important Notes for Women and Finasteride
Finasteride is not approved for use in women, especially those who are pregnant or may become pregnant, because it can cause serious birth defects in male babies. Some doctors may prescribe it off label for postmenopausal women who are not at risk of pregnancy, but this must be carefully managed by a medical professional. Even topical finasteride should be handled with caution. Women who are pregnant should avoid touching or applying it.
What to Expect When Taking Finasteride
Finasteride is not a quick fix. Whether you choose the oral or topical version, it takes three to six months to start seeing results and up to two years for the full effect. It must be used continuously as well. If you stop, the benefits will fade, and hair loss will return. Given the need for long-term use, some people find compliance is less of a challenge with an oral treatment.
Consistency and patience are key. Many men find that combining finasteride with other treatments, such as minoxidil, platelet-rich plasma (PRP) therapy, AlmaTED or Folix can offer even better long-term results.
Should I use Oral Finasteride or Topical Finasteride?
Both topical and oral finasteride can be effective options for fighting hair loss. The oral form is FDA approved and supported by decades of research, while topical finasteride shows promising results with fewer systemic effects but is still considered off label in the United States. Oral finasteride is an inexpensive, generic medication; since topical finasteride has to be compounded (mixed by hand), it is currently more expensive.
If you are deciding between them, talk with a hair loss specialist or dermatologist. They can help you weigh the pros and cons, monitor for side effects, and choose the treatment plan that best fits your goals and comfort level.
With proper use and guidance, finasteride, whether taken by mouth or applied to the scalp, can make a real difference in preserving and restoring your hair.
