01Where does the fifty-percent line come from?
In men with benign prostatic hyperplasia treated with 5 mg finasteride, PSA levels are decreased by approximately 50 percent. Other 5 mg studies showed decreases even in the presence of prostate cancer. Those findings are taken into account when someone on finasteride is evaluated. The 1 mg hair pair is the 0.7 to 0.5 ng/mL read, not that same 50 percent. The clinician adjusts the read for the tablet you actually take. A home rule of 'always double it' belongs to the 5 mg counseling habit, not to a number you invent for 1 mg.
02What happened to PSA on the 1 mg hair studies?
In men treated with Propecia, serum PSA decreased from 0.7 ng/mL at baseline to 0.5 ng/mL at month 12. That is the hair-study pair on the Warnings page. It is two means, not a 50 percent claim invented for 1 mg. The clinician still has to interpret a later number against that drop. A result that looks 'normal' for a man not on a 5-alpha-reductase inhibitor can still be a rise from your own lowest point. Do not multiply 1 mg by two at home. Bring the medication list to the draw.
03What if I skipped tablets before the blood draw?
Tell the clinician if you have not been taking Propecia as prescribed, because that may affect the PSA results. A holiday before the test is not a clean baseline. It is a mixed signal. Stopping also reverses the hair effect within 12 months. Do not invent a washout week to 'help' the lab. See how long to stay on. Keep the daily 1 mg line through the draw unless the clinician stops it for another reason. A mixed week of tablets makes the lowest-point story harder to read.
04Do I tell the lab I take the hair tablet?
Tell the healthcare provider that you are taking Propecia, because the tablet decreases PSA. Changes have to be evaluated by that person, not by the reference range alone. The 1 mg dose page is what belongs on the medication list. A dermatology label does not hide the tablet from a urology draw. Name the milligram. A list that only says 'hair pill' does not help the person reading the number. Say finasteride 1 mg, or Propecia, and how steadily you have been taking it.
05What if PSA later rises from its lowest point?
Any confirmed increase from the lowest PSA value while on Propecia may signal the presence of prostate cancer and should be evaluated, even if the number is still inside the usual range for men not taking a 5-alpha-reductase inhibitor. The label does not treat a 'normal' printout as the end of the question. Repeat the test if the first rise is messy. Then work up a confirmed climb. A missed week of tablets before that draw can also muddy the lowest-point story. Tell the clinician about those misses.
06Does the hair label mention high-grade prostate cancer?
Men aged 55 and over with a normal digital rectal exam and PSA of 3.0 ng/mL or less at baseline, taking 5 mg finasteride in the Prostate Cancer Prevention Trial, had an increased risk of Gleason score 8-10 prostate cancer: 1.8 percent versus 1.1 percent on placebo. Whether that finding applies to Propecia use is unknown on the label. The clinical significance with respect to Propecia in men is unknown. The tablet is not approved to reduce prostate-cancer risk. That warning sits on the 1 mg prescribing information even though PCPT used 5 mg. It is not a 1 mg event rate you can paste onto your bottle.