Finasteride 1 mg vs 5 mg: Propecia, proscar and hair loss

Finasteride 5 mg and finasteride 1 mg are the same drug at two strengths, approved for two different conditions. The 5 mg tablet (Proscar) is FDA-approved for an enlarged prostate, so taking it for hair loss is off-label; the 1 mg tablet (Propecia) is the one approved for male pattern hair loss, and in the trials that set the dose, 5 mg grew no more hair than 1 mg (Roberts et al.).

Here is how the two compare on approval, dose response, side effects and cost, and what to know if a prescriber suggests splitting 5 mg tablets.

Proscar vs Propecia at a glance

Both are made by Organon, both are sold as generics, and both carry the same core warnings: women who are or may be pregnant should not handle crushed or broken tablets, finasteride lowers PSA, and 5-alpha reductase inhibitors may raise the risk of high-grade prostate cancer (Proscar label, Propecia label).

What the dose trials found

Finasteride blocks 5-alpha reductase type II, the enzyme that turns testosterone into DHT, the hormone that shrinks follicles in pattern hair loss. Two 1999 papers describe the studies behind the hair loss dose.

In the first, 249 men with hair loss had scalp biopsies before and after 42 days on finasteride or placebo (Drake et al.):

The authors concluded that doses as low as 0.2 mg a day lowered scalp and blood DHT about as much as the higher doses. Going from 1 mg to 5 mg added little.

The second set were clinical trials in men aged 18 to 36 with moderate hair loss on the crown, who took 5 mg, 1 mg, 0.2 mg or 0.01 mg a day or placebo. Doses of 0.2 mg and above worked on every measure (hair counts, the men’s own ratings, investigator ratings and photos). The 1 mg and 5 mg doses were similar and better than the lower doses, and 0.01 mg did no better than placebo. The researchers named 1 mg the optimal dose and took it forward for further development.

A 2022 review with a network meta-analysis of the trials reached the same answer: the efficacy of 5 mg and 1 mg a day was not significantly different (Gupta et al.).

Finasteride 5 mg for hair loss is off-label

Off-label prescribing is legal when a clinician judges it right for you, and finasteride is not a controlled substance. But the 5 mg dose was approved on prostate trials in older men, not hair loss trials, and the dose trials above found no extra hair from it. If a prescriber suggests 5 mg, it is fair to ask why, and whether the plan is to take a whole tablet or a piece of one.

Finasteride at any dose is not approved for women. The Propecia label reports that in a 12-month study of 137 postmenopausal women with hair loss, 1 mg did no better than placebo, and it is contraindicated in pregnancy. See finasteride for women for what is known about higher doses in women.

Side effects at 1 mg and 5 mg

The labels give first-year rates of drug-related sexual side effects from each program:

Scroll sideways to see the full table

The numbers look very different, but the men were too. The 5 mg trial enrolled older men with prostate enlargement, whose placebo groups also had far higher rates, and the labels say rates from different trials can’t be directly compared. In both programs the effects faded over time: at 5 mg, there was no significant difference from placebo in years 2 to 4, and at 1 mg each effect fell to 0.3% or less by year 5.

One measure was compared across doses. In healthy men, 1 mg for 48 weeks lowered median ejaculate volume by 0.3 mL (11%), against 0.2 mL (8%) on placebo, while two studies of 5 mg found median drops of about 0.5 mL (25%) compared with placebo, which reversed after stopping.

Both labels list the same postmarketing reports: depression, suicidal ideation, sexual problems that continued after stopping, male infertility and poor semen quality, and male breast cancer. The high-grade prostate cancer figures come from 5 mg: in the 7-year Prostate Cancer Prevention Trial of 18,882 men aged 55 and older, Gleason 8 to 10 cancer was found in 1.8% on finasteride against 1.1% on placebo. The Propecia label says the significance of this for men taking 1 mg is unknown. Our finasteride side effects guide covers each warning.

Why some men split 5 mg tablets

Cutting a 5 mg tablet into quarters gives about 1.25 mg a dose, close to the hair loss dose, so one tablet covers four days. It is usually done to lower the cost per dose. Before you try it, know what the labels and the FDA say:

• Proscar isn’t scored. Its label describes a film-coated, apple-shaped tablet with no score line. The FDA says that when a label doesn’t say a tablet can be split, it has not evaluated whether the pieces are the same in weight or drug content, or work the same way as the whole tablet (FDA).
• Generics differ. The FDA notes that the same medicine can be made differently, so check whether a new generic can be split even if your old one could.
• Split one at a time. The FDA advises taking all pieces of one tablet before splitting the next, because heat and moisture can affect split tablets.
• Keep pieces away from pregnant women. The coating prevents contact with finasteride during normal handling, but only while the tablet is intact. Women who are or may be pregnant should not handle crushed or broken tablets, and a pregnant woman who touches one should wash the area with soap and water right away.

Tablet splitting should be done only under a clinician’s supervision, the FDA says.

PSA and prostate checks

Both strengths lower PSA, the prostate cancer screening test. At 1 mg, mean PSA in men aged 18 to 41 fell from 0.7 to 0.5 ng/mL at 12 months. At 5 mg, PSA falls by about 50% within 6 months, and the Proscar label says a PSA result in a man on it for 6 months or more should be doubled before comparing it with normal ranges. On either dose, any confirmed rise from your lowest PSA should be checked, and whoever orders the test should know you take finasteride.

What finasteride costs online

These are prices from the online providers we compare, as of October 2026:

None of these providers lists a 5 mg tablet, so the hair loss dose is what they sell. See our cheapest finasteride list for every published price, our guide to getting a finasteride prescription online, and the oral finasteride page for the full label summary.

The bottom line

Finasteride 1 mg is the FDA-approved hair loss dose, and in the trials that set it, 5 mg grew no more hair while lowering ejaculate volume more. Finasteride 5 mg is a prostate drug, off-label for hair, and its tablets aren’t scored for splitting. If you are weighing doses or forms, see topical vs oral finasteride and dutasteride vs finasteride, or compare providers on our hair loss hub.