Does Propecia (Finasteride) Work?

  • Medically reviewed by: Dr. Anil Simhadri
  • Written by: William Slator
  • Last updated: 06/12/2023

Millions of men in the United States have now tried Propecia for their hair loss. Released more than two decades ago, it remains the number one prescribed oral medication for hair loss both in the United States and globally. This article will explain exactly how effective it is, allowing the reader to make a more informed decision on its usage.

This article is for educational purposes only, and you should speak to your doctor before starting treatment. Finasteride is a prescription-only medication and one that should not be started without careful consideration and expert medical guidance.

This article will review:

  1. How it works
  2. What to expect when taking it for the first time
  3. How and when to take it
  4. Results you can expect
  5. When to stop taking it
  6. Potential side effects
  7. Other options to try if it is not effective for you
  8. Conclusion

How Finasteride Works

Finasteride is the active ingredient in the popular hair loss drug Propecia. This was originally developed by pharmaceutical company Merck to treat male prostate enlargement, and in 1997 it was approved by the FDA as a treatment for male Androgenetic Alopecia (AGA) (1).

Androgenetic alopecia accounts for well over 95% of cases of hair loss in men and is thought to be caused by a sensitivity to the male hormone dihydrotestosterone (DHT). DHT is believed to progressively shrink the genetically susceptible hair follicles on the frontal and vertex area of the scalp in a process called hair follicle miniaturization. Eventually, the follicles shrink to such a degree that the hair shaft does not even protrude from the scalp, with the result that it goes completely bald.

DHT is synthesized in the human body via testosterone, but for this chemical reaction to take place an enzyme called 5-alpha-reductase is necessary. In the absence of 5-alpha-reductase, the production of DHT in the body falls to near-zero levels.

Finasteride works by inhibiting this enzyme, which it does by binding to the enzyme and rendering it inactive (2). With 5-alpha-reductase inhibited, DHT levels in the body decline dramatically. The hair follicle miniaturization process is paused, and often even partially reversed.

What to Expect When Using Finasteride

The typical user should not expect dramatic regrowth from finasteride and certainly not overnight. Because hair growth is subject to a lengthy hair growth cycle, you can expect to see little in the way of results for the first three months. After the three-month mark, you can expect the first signs of regrowth which will become more pronounced at six months. You get your final results with finasteride at around the 12-month mark, after which you are unlikely to grow further hair.

One thing to look out for if taking finasteride for the first time is the appearance of side effects, which will be covered in more detail shortly.

How to Take Finasteride

The recommended dosage is 1mg per day. You can take it any time of day, though ideally at the same time. If you forget to take your pill, do not attempt to compensate by taking two pills the following day. Just continue to take your daily pill as if you have never missed a dose. You can take it on an empty or full stomach; it makes no difference.

Results You Might Expect

The strength of Propecia lies in its ability to stop further hair loss for most men (3). The majority of studies agree that between 80 to 90% of men will stop losing hair on Propecia and that this effect will last for a minimum of five years. In other words, your body does not quickly become tolerant to the effects of finasteride.

When it comes to regrowing hair, the results are far more modest. Around two-thirds of users will see some regrowth ranging from barely perceptible to significant.

The crown or vertex area of the head will generally respond better compared to frontal areas, though this is true for most hair loss treatments.

With regards to parts of the head that have gone completely bald, finasteride has next to zero effect. Once the scalp has progressed to complete baldness, finasteride is not a useful treatment option. The only realistic option for those areas is a hair transplant.

Like most other hair loss treatments, the positive effects only last as long as the treatment. FInasteride does not treat hair loss permanently. Instead, it temporarily blocks DHT. When you stop treatment, any hair you have regrown may fall once again and your hair loss will resume its normal course.

When to Stop Taking Finasteride

Perhaps the most common mistake that users make is not allowing finasteride enough time and discontinuing treatment due to impatience.

Just as you lost your hair very gradually in the first place, you will also regain it very gradually. You need at least three months to see the first signs of regrowth, but up to 12 months for full results. If you are not satisfied with the results after this time, you should stop treatment.

The other scenario where you want to consider stopping finasteride is if you develop side effects.

Potential Side Effects

Finasteride has now been on the market for decades, meaning researchers have a decent idea of its safety profile and side effects (4).

Because finasteride is not a targeted medication but it instead blocks DHT systemically, the side effects will not manifest at the scalp. Instead, to the degree that you get side effects, these will tend to be of a hormonal or sexual nature (5).

The most common side effects are loss of libido and erectile dysfunction, which can range from slightly softer erections to complete impotence. The percentage of men who will develop these side effects varies from study to study, from 3% or less to 8% or more.

Another common side effect is gynecomastia, which is the swelling and tenderness of the breast tissue underneath the nipple area (6). If this is allowed to persist it can become permanent, meaning only surgery can correct it.

These side effects can take a few days to weeks or even months to manifest after you’ve started treatment. If they do appear, there are two basic options that you can discuss with your doctor: a) reduce the dosage, or b) stop treatment altogether.

When it comes to lowering the dosage, there is evidence that a dosage as low as one-fifth of the recommended 1mg daily can stop hair loss while dramatically reducing the risk of side effects (7). After consultation with your doctor, you can switch to the lower dosage and see if the side effects persist. If they do, there is no option but to stop treatment.

Upon discontinuing treatment, the sexual side effects should go away. Finasteride has a very short half-life, and after a few weeks, it will leave your system without a trace. There is a small minority of users for whom the side effects will persist when the patient comes off finasteride. When this happens it is usually accompanied by other symptoms like fatigue, depression, and anxiety. Why this phenomenon happens is still a mystery, and some researchers dismiss it as a possibility altogether (8).

Another thing to consider is that finasteride may affect sperm counts and quality, at least for the first few weeks. Whether these changes are significant enough to affect fertility is debated. At any rate, if you are trying for a child it is a good idea to discontinue treatment, at least temporarily (9).

Having said that, there is no risk to the fetus from taking finasteride. The amount of finasteride present in the semen (and which passes on to the women through sex) is minuscule. Finasteride tablets are coated for added protection to ensure the drug does not come into contact with a woman who is pregnant or trying to conceive. For that reason, it is important to never crush the pill but swallow it whole.

One final point that will be important to older men involves the drug’s interaction with PSA levels (10). Finasteride is known to drastically lower PSA levels, making the results of any test difficult to interpret. If you are experiencing issues with your prostate and are taking finasteride, it is something you should bring to the attention of your doctor.

Alternatives to Finasteride

If you find finasteride does not work for you, there are other treatment options to consider though many will not be as attractive as Propecia (11).

Minoxidil (brand name Rogaine) is an FDA-approved topical medication that gives similar results as Propecia (12). The major disadvantage of minoxidil is that it needs to be applied on the scalp twice daily, which will make it an impractical solution for many men.

Other options to consider are natural 5-alpha-reductase inhibitors, most notably saw palmetto extract. Being a naturally occurring plant that cannot be patented, there is no incentive for a pharmaceutical company to seek FDA approval for hair loss. Nevertheless, there is evidence that saw palmetto is about half to two-thirds as effective as finasteride (13).

Other options to consider include Low-Level Light Therapy (LLLT), which is a form of light therapy that stimulates hair growth and can be done at home via specialized helmets or caps (14). These have practically no side effects, though hair regrowth is modest compared to finasteride.

Finally, there are surgical options including Follicular Unit Extraction (FUE) and Follicular Unit Transplantation (FUT) (15). While these will give generally better and more long-lasting results, they are surgical procedures and require a far larger budget.


Despite the fact it is nearly 40 years since its discovery, finasteride remains the frontline of hair loss treatments. It works to stop hair loss in the majority of users, meaning that if treatment is started early enough, a cosmetically acceptable head of hair can be maintained indefinitely. As such, it is one of the first options to consider if you have just been diagnosed with hair loss.

Having said that, it is important to understand that regrowth will typically be modest. Also, you are not curing your hair loss with finasteride, but merely masking the symptoms. These symptoms will reappear when you discontinue treatment, at which point your hair loss will resume its normal course.

Your doctor can provide more information on finasteride, including potential side effects and what can be done to mitigate them.

To learn more about finasteride, you can view our comprehensive guide on the Hairguard YouTube channel:

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