Finasteride lowers DHT, the hormone that shrinks hair follicles in male pattern hair loss. It is FDA-approved for men only, takes three months or more to show benefit, and carries label warnings on sexual side effects, mood, PSA testing and pregnancy exposure.
Finasteride is a prescription tablet that treats male pattern hair loss by lowering dihydrotestosterone (DHT), the hormone linked to the gradual shrinking of scalp follicles. It is FDA-approved for men only, its label says three months or more of daily use is generally needed before benefit appears, and the benefit reverses within about a year of stopping. Its label also carries important warnings about sexual side effects, mood changes, PSA blood tests and exposure during pregnancy. As for the much-discussed "early shedding phase," the research is thinner than online forums suggest, and this article explains what is and is not known.
According to the prescribing information, finasteride is a specific inhibitor of type II 5-alpha reductase, an enzyme that converts testosterone into DHT. The label notes that the balding scalp contains miniaturized hair follicles and more DHT than scalp with full hair, and that finasteride lowers DHT in both the scalp and the blood. A single tablet reduces blood DHT by about 65 percent within 24 hours. Finasteride does not bind to the androgen receptor itself, and testosterone levels rise slightly but stay within the normal range.
Lowering DHT does not instantly change how hair looks. Follicles need time to cycle, which is why the label describes a wait of three months or more. The AAD gives a similar estimate, saying it usually takes about 4 months to notice improvement.
The label summarizes three 12-month, placebo-controlled trials in 1,879 men aged 18 to 41 with mild to moderate hair loss, with extension studies running up to five years.
The label also notes that effectiveness at the temples (bitemporal recession) has not been established, and that in a study of postmenopausal women, finasteride did not improve hair. These are averages from controlled trials, and individual results vary.
A 2000 letter in the Journal of the American Academy of Dermatology by Tosti and Piraccini offers a useful way to think about these results. The authors proposed that in the first year, finasteride helps resting follicles re-enter the growth phase (raising hair counts), and later it lengthens the growth phase so existing hairs become thicker and longer. That is one reason men may keep noticing improvement after the hair count levels off.
Many people have heard that finasteride causes a temporary "shed" in the first few months. The evidence here is limited, so it is worth being precise.
A 2025 review in SKIN The Journal of Cutaneous Medicine looked at treatment-related shedding across hair loss therapies. It found that shedding is well described with topical and oral minoxidil. For finasteride and similar medications, the authors reported that randomized trials showed increased hair counts at weeks 12 and 24 but did not describe a distinct shedding phase before that. They concluded that evidence for a shedding phase with these drugs is lacking, although a temporary shed is possible in theory as follicles respond to changing hormone levels. They also noted that most trials did not measure results until about 90 days in, so early shedding could be under-recognized.
The practical takeaway: some people do notice more hair in the first weeks, and it may reflect follicles cycling into a new growth phase. But the AAD notes that increased shedding has many other triggers, including high stress, fever or illness, and surgery, and that hereditary hair loss itself continues until treated. If shedding is heavy or lasts more than a few months, check in with your prescriber rather than assuming it is part of the process.
In the 12-month trials, the label reports these rates of drug-related side effects:
| Side effect | Finasteride | Placebo |
|---|---|---|
| Decreased libido | 1.8% | 1.3% |
| Erectile dysfunction | 1.3% | 0.7% |
| Ejaculation disorder | 1.2% | 0.7% |
Overall, 3.8 percent of men on finasteride reported one or more of these, versus 2.1 percent on placebo. The label states these resolved in men who stopped the medication and in most who continued, and that each fell to 0.3 percent or less by the fifth year.
The label also lists adverse reactions identified after the drug reached the market. It cautions that because these are reported voluntarily, it is not always possible to estimate how often they occur or prove they were caused by the drug. They include:
The label asks patients to promptly report any breast changes such as lumps, pain or nipple discharge. If you notice mood changes, low mood or thoughts of self-harm, contact your prescriber right away. If you are in crisis, call or text 988, or call 911 in an emergency.
The label lists pregnancy as a contraindication, because blocking DHT can affect the development of a male fetus. Women who are or may become pregnant should not handle crushed or broken tablets. Intact tablets are coated, which prevents contact during normal handling. If contact with a broken tablet happens, the label says to wash the area right away with soap and water. The label also describes a study of semen levels in men taking finasteride, which estimated that potential exposure to a partner was about 650-fold lower than an amount that had no effect on DHT in men.
Finasteride lowers prostate-specific antigen (PSA), a blood test used in prostate cancer screening. In the hair loss trials, average PSA fell from 0.7 to 0.5 ng/mL at 12 months. The label advises that any confirmed rise in PSA while on finasteride should be evaluated, even if it is still within the normal range. In a large prostate cancer prevention trial using a higher dose in older men, high-grade prostate cancer was found in 1.8 percent of men on finasteride versus 1.1 percent on placebo, and the label notes that 5-alpha reductase inhibitors may increase that risk.
There are no FDA-approved topical finasteride products, and compounded versions are not FDA-approved. In 2025, the FDA reported 32 adverse event cases linked to compounded topical finasteride, describing effects similar to those of the tablets, and noted that most reports said symptoms persisted after stopping. The FDA also pointed out that topical products have no protective coating, raising the risk of accidental transfer to others.
The label says daily use for three months or more is generally needed before benefit is seen, and trial investigators noted improvement as early as 3 months. The AAD suggests about 4 months to notice a change. Your prescriber will re-evaluate whether it is helping over time.
According to the label, stopping reverses the effect within 12 months. In the trials, men switched from finasteride to placebo lost the hair count gains they had made by 24 months.
Finasteride is not indicated for women, and it is contraindicated in pregnancy. In a 12-month study of postmenopausal women described in the label, it did not improve hair.
Oral finasteride is an FDA-approved medication (Propecia is the brand name). NewDay Wellness lists oral finasteride as coming soon and does not offer it at this time. Topical finasteride, by contrast, is only available as a compounded product, which is not FDA-approved.
Before starting finasteride, share your full medical history with a licensed provider, including any history of depression, fertility plans, prostate screening and other medications. Your prescriber decides whether it is appropriate and sets the dose. You can learn more on the finasteride product page. This article is educational and does not determine eligibility for any treatment.
Written by the NewDay Wellness editorial team from the sources above and checked against them before publication, and medically reviewed by Dr. Sean Arora and Dr. Shannon Arora of Arora Health & Aesthetics; see our editorial standards. This article is educational and does not diagnose conditions, establish eligibility for any medication, or replace care from a licensed provider. Compounded medications are not FDA-approved.
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