Finasteride and PSA: Why It Reads 40-50% Lower

Daily finasteride 1 mg can push your PSA result down by roughly 40 to 50%. That's why your checkup doctor needs to know you take it, when you started, and whether your PSA has crept back up from its lowest point while you've been on it.

Why Does a Hair Loss Pill Lower Your PSA?

Why Does a Hair Loss Pill Lower Your PSA?

Finasteride blocks the enzyme that turns testosterone into DHT, a stronger male hormone. The type of enzyme it targets, called type II 5-alpha reductase, sits mainly in hair follicles and in the prostate. So a pill you take for your scalp works on your prostate too.

PSA (prostate-specific antigen): A protein made by the prostate that shows up in a blood test. It's used to screen for prostate cancer early.

In men with male pattern hair loss, balding areas of the scalp hold shrunken follicles and more DHT than areas with full hair. Finasteride 1 mg is FDA-approved to treat male pattern hair loss in men, and it lowers DHT in both the scalp and the blood. With less DHT stimulating the prostate, PSA reads lower as well. In men aged 18 to 41 who took 1 mg for 12 months, average PSA went from 0.7 to 0.5 ng/mL*.

Based on the US FDA prescribing information for Propecia (finasteride 1 mg).

That drop looks tiny in younger men because their starting numbers are already low. As you get older and your baseline rises, the same percentage takes a bigger bite out of the result. If you only glance at the word "normal" on your report, you lose track of what your true number would have been.

Why Does a Hair Loss Pill Lower Your PSA?

How Much Lower Does PSA Go, and How Soon?

How Much Lower Does PSA Go, and How Soon?

For men in their 40s and 50s, PSA falls by close to half over the first year. In a trial of 355 men with hair loss who were randomly split 4 to 1 between finasteride 1 mg and a placebo, median PSA dropped 40% in men aged 40 to 49 and 50% in men aged 50 to 60 after 48 weeks. On placebo, it didn't change in the younger group and rose 13% in the older one. Based on those numbers, the authors concluded that the adjustment already used for men on 5 mg (reading the result as roughly double) should apply to the 1 mg dose too.

Real-world records from Korea tell a slightly different story. Among 1,379 men whose starting PSA was under 2.5 ng/mL, the overall drop was 27.8%. About 79.3% saw their PSA fall, while 20.7% stayed the same or went up. Men who started below 0.5 ng/mL didn't show a clear drug-related drop. Even after only 3 to 6 months of treatment, PSA was 26.0% lower.

How Much Lower Does PSA Go, and How Soon?

Put together, it's fair to assume your PSA reads lower than it would without the drug. How much lower depends on your age and your starting number, though, so nobody can recalculate your exact "true" PSA from one result. Individual results vary.

What Should You Tell Your Checkup Doctor?

What Should You Tell Your Checkup Doctor?

Your doctor can only read PSA correctly if they know you're on the drug and for how long. If you list your hair loss pill as a "supplement" or leave it off the intake form, a low result simply gets read as normal. Bring these four details:

• The drug name and daily dose (finasteride 1 mg, dutasteride, and so on)
• The month you started and how long you've been taking it
• Whether you often skip doses, or recently stopped and restarted
• Any PSA result from before you started, with the date

Skipping doses can also throw off your PSA. While you're on finasteride, a confirmed rise from your lowest PSA should be checked, even if it's still inside the normal range for men who don't take the drug*.

Based on the US FDA prescribing information for Propecia (finasteride 1 mg).

That said, one high reading doesn't send you straight to more tests. A newly raised PSA returns to the normal range on a repeat test in 25 to 40% of men, so confirming it with a second test a few months later is the usual next step*. Whether to double the number and when to retest are calls for your checkup doctor or a urologist.

Based on the American Urological Association guideline on early detection of prostate cancer.

Can Finasteride Hide or Raise Prostate Cancer Risk?

Can Finasteride Hide or Raise Prostate Cancer Risk?

A low PSA on finasteride doesn't mean you can stop thinking about prostate cancer. At 5 mg, five times the hair loss dose, finasteride can lower PSA even when prostate cancer is present. That's why the trend from your lowest number matters more than any single value.

In a 7-year trial, 18,882 men aged 55 and older took either 5 mg or a placebo. Prostate cancer was found in 18.4% of the finasteride group versus 24.4% of the placebo group. On the other hand, high-grade cancer (Gleason score 8 to 10) showed up slightly more often, in 1.8% versus 1.1%. When the same men were followed for up to 18 years, overall survival was about the same in both groups (78.0% and 78.2% at 15 years).

Gleason score: A grade given to a prostate biopsy that shows how aggressive the cancer cells look. A higher score means a more aggressive cancer.

These results come from a dose five times higher than the hair loss pill, so they don't transfer directly to 1 mg. While you're taking finasteride for hair loss, tell the doctor who prescribed it right away, without waiting for your next checkup, if you notice:

• A lump or pain in your breast area
• Discharge from a nipple
• Lower sex drive or erection problems that don't go away

Fitting a Hair Loss Visit Into a Seoul Trip

Fitting a Hair Loss Visit Into a Seoul Trip

Unless you've had IV sedation that day, there's no reason to delay a flight after a visit for hair loss. Hair loss pills also work slowly, since daily use for 3 months or more is usually needed before you see a benefit.

Most treatments change things gradually rather than all at once, and one visit is a starting point, not a finished plan. After you fly home, you can send photos and your latest test results to the clinic on WhatsApp if questions come up. If you notice strong warning signs, such as a breast lump or ongoing erection problems, see a local doctor first.

What to Bring to Your Next Checkup

Write the month you started finasteride and every PSA result since then on one page, in date order. That way your checkup doctor can see right away whether this year's number has risen from your lowest point. If this is your first PSA test, simply noting that you're on the drug makes next year's comparison easier. Get prostate questions answered by your checkup doctor or a urologist, and talk to the doctor who prescribed your pill before changing how you take it. STON Clinic is in Seoul's Myeongdong area, inside Lotte Hotel Seoul near Euljiro 1-ga Station. When you reach out on WhatsApp, include the drug name and dose and when you started, and mention whether you have a recent PSA result.