Finasteride 5mg is primarily used to treat benign prostatic hyperplasia (BPH), commonly known as an enlarged prostate. First approved for this purpose in 1992, it remains one of the most widely prescribed medications for men experiencing urinary symptoms caused by prostate growth. A lower dose (1mg) is used separately for male pattern hair loss, but the 5mg tablet is specifically designed for prostate management.
How Finasteride Works
Your body naturally converts testosterone into a more potent hormone called dihydrotestosterone, or DHT. This conversion is carried out by an enzyme, and DHT is the key driver of prostate growth in adulthood. Finasteride blocks that enzyme, cutting DHT levels in the blood by roughly 70% and in the prostate itself by about 90%. With less DHT stimulating growth, the prostate gradually shrinks.
This isn’t a fast process. The prostate took years to enlarge, and reversing that takes months. Most men won’t notice meaningful symptom improvement in the first six months. Clinical trials consistently show that finasteride doesn’t outperform placebo in short-term use (under a year), but after 12 months and beyond, the differences become significant and continue to grow. In one study, prostate volume dropped by 27% after the first year on 5mg and by 43% at three years.
What Symptoms It Treats
An enlarged prostate squeezes the urethra, making it harder to urinate. The symptoms are familiar to millions of men over 50: a weak stream, difficulty starting urination, frequent trips to the bathroom at night, and the feeling that your bladder hasn’t fully emptied. Finasteride addresses these by physically reducing the size of the gland pressing on the urethra.
In clinical trials, men taking finasteride 5mg saw their symptom scores drop by roughly 5 points on the standard 35-point scale used to measure urinary bother, compared to less than 2 points for men on placebo. Maximum urinary flow rate improved by 35% at one year and held at 36% at three years. These are moderate but real improvements, and they tend to hold steady or continue improving with longer use.
Reducing the Risk of Surgery and Emergencies
Beyond day-to-day symptom relief, finasteride 5mg has a second, arguably more important benefit: it lowers the risk of BPH getting worse. Left untreated, an enlarged prostate can eventually block urine flow completely, a painful emergency called acute urinary retention that requires a catheter. Many men with advancing BPH also end up needing surgical procedures to remove or reduce prostate tissue.
In a large pooled analysis, finasteride cut the risk of acute urinary retention by 57% over two years compared to placebo. It reduced the need for surgical intervention by 34%. The MTOPS study, one of the longest and largest BPH trials, found even greater reductions: 68% lower risk of urinary retention and 64% lower risk of surgery. For men with larger prostates who face the highest odds of these outcomes, this preventive effect is often the primary reason doctors prescribe finasteride rather than medications that only relax the muscle around the prostate.
Finasteride 5mg vs. 1mg
The two doses serve different conditions and are sold under different brand names. The 5mg tablet (brand name Proscar) treats enlarged prostate. The 1mg tablet (brand name Propecia) treats male pattern hair loss. Both work through the same mechanism of blocking DHT, but the prostate requires a higher dose because of how much DHT concentrates in that tissue. Your doctor won’t prescribe the 5mg dose for hair loss alone, and the 1mg dose isn’t sufficient for managing BPH.
Off-Label Uses
Because finasteride suppresses DHT so effectively, doctors sometimes prescribe the 5mg dose for conditions beyond BPH. These include excessive hair growth (hirsutism) in women with elevated androgen levels, female pattern hair loss in postmenopausal women, and as part of gender-affirming hormone therapy. These are off-label uses, meaning the drug hasn’t been formally approved for these purposes, but clinical evidence supports its effectiveness in certain patients.
Side Effects and What to Expect
Sexual side effects are the most discussed concern with finasteride. In clinical trials, erectile difficulty, reduced sex drive, and ejaculatory changes occurred in roughly 2% to 4% of men, though some studies report higher rates depending on how the question was asked. The encouraging pattern is that these side effects tend to fade with continued use. By the fifth year of treatment, the incidence of each dropped to 0.3% or lower. Many men who experience sexual side effects in the first few months find they resolve even without stopping the medication.
Breast tenderness or slight enlargement can occur in a small number of men. This is also related to the shift in hormone balance when DHT is suppressed.
Effect on PSA Testing
If you take finasteride 5mg, it will lower your PSA level, the blood marker used to screen for prostate cancer. This doesn’t mean it protects against cancer; it simply changes the baseline reading. Doctors typically multiply your PSA result by 2 during the first few years on the medication, and by 2.3 after three or more years, to get an accurate comparison. Make sure any doctor ordering a PSA test knows you’re taking finasteride, because an uncorrected reading could mask a rising PSA that deserves further investigation.
Handling Precautions
Finasteride can be absorbed through the skin and poses a serious risk to developing male fetuses. Women who are pregnant or could become pregnant should never handle crushed or broken finasteride tablets. Intact tablets have a coating that prevents skin absorption, but if a tablet is damaged and skin contact occurs, the area should be washed immediately with soap and water. This precaution also applies to children.
How Long Treatment Lasts
Finasteride for BPH is generally a long-term medication. Because it works by keeping DHT suppressed, the prostate will begin to grow again if you stop taking it, and symptoms typically return within several months. The benefits continue to accumulate over years of use, with prostate volume reductions reaching over 40% at the three-year mark and surgical risk continuing to stay low. Most men who respond well to finasteride stay on it indefinitely, taking one 5mg tablet daily.