Does Finasteride Reduce Testosterone?
No, finasteride does not reduce testosterone. It blocks the enzyme that turns testosterone into DHT, the hormone that shrinks hair follicles. DHT is what falls. In a 2004 trial of men with an enlarged prostate of 5 mg, testosterone rose slightly but stayed normal. In a 1999 study of 249 men with hair loss, 1 mg a day cut blood DHT by 71.4% within 42 days. Some men notice sexual side effects, which are not the same as low testosterone.
How Does Finasteride Lower DHT Without Lowering Testosterone?
Finasteride blocks type 2 5-alpha reductase, the enzyme that turns testosterone into DHT. So less DHT is made, while testosterone itself is not removed.
In men with pattern hair loss, DHT slowly shrinks hair follicles on the top of the head.
With less of the enzyme at work, less testosterone becomes DHT. Finasteride lowers DHT in both the blood and the scalp.
So finasteride does not remove testosterone. It changes how much of it is turned into DHT.
What Happens to Testosterone Levels on Finasteride?
Testosterone usually stays in the normal range and may rise slightly. Less of it is being turned into DHT, so slightly more stays in the blood.
A 2004 trial in men with an enlarged prostate compared finasteride with dutasteride, a stronger DHT blocker. In every group, average testosterone rose but stayed within the normal range. That trial used 5 mg of finasteride, five times the hair loss dose.
For hair loss, the dose is 1 mg a day. The 2004 trial did not test this dose, so its testosterone result is a guide, not a direct measure. The drop in DHT is what treats hair loss.
How Much Does Finasteride Lower DHT?
At the hair loss dose, finasteride lowers blood DHT by about 70%. A higher dose adds very little.
A 1999 dose study of 249 men with pattern hair loss tested five doses for 42 days. It measured DHT in both the blood and the scalp. Doses as low as 0.2 mg already gave close to the full drop.
This is why 1 mg is the standard dose for hair. Going higher does not lower DHT much more. In the 2004 prostate trial, 5 mg of finasteride lowered DHT by 70.8% on average. Dutasteride at 0.5 mg lowered it by 94.7%.
Will Blocking DHT Lower Testosterone?
No. Blocking DHT means less testosterone is converted, so testosterone stays in the blood and DHT is what falls. Finasteride lowers one hormone and leaves the other in the normal range.
Why Do Men Link Finasteride With Low Testosterone?
Men often link the two because finasteride can cause sexual side effects in a small share of users. These can feel like low testosterone, but they are not the same thing.
A 2019 review of 15 placebo-controlled trials with 4,495 men looked at sexual side effects of DHT blockers for hair loss. Men on finasteride were about 1.66 times as likely as men on placebo to report a sexual side effect.
India's dermatology body, the IADVL, covers this in its 2016 finasteride guideline. In controlled trials, 3.8% of men on 1 mg reported a sexual side effect. On placebo, the figure was 2.1%.
The US National Library of Medicine's MedlinePlus guide to finasteride lists lower sex drive, trouble getting an erection and changes in ejaculation among the possible effects. Tell your doctor if any of these happen. To see what finasteride can do for hair, read our guide on whether finasteride regrows hair.
Can Finasteride Sexual Side Effects Last After Stopping?
Sexual side effects usually reverse after stopping, says the IADVL guideline. But some men report effects that continue after they stop, and a clear cause has not been established.
The guideline cites trials reviewed by the US FDA. In them, most of these effects returned to normal within three months of stopping. The guideline notes that the US label was updated in 2012 to mention these reports, and that a clear cause-and-effect link has not been shown.
So how often lasting effects happen is not known.
If any sexual change worries you, speak to your doctor. Do not ignore symptoms that last, and do not stop or restart the drug on your own.
Is Topical Finasteride Easier on Hormones?
Topical finasteride puts much less of the drug into the blood, so it lowers blood DHT less than tablets. In a 2022 European trial of 458 men, a finasteride scalp spray cut blood DHT by 34.5%. Tablets cut it by 55.6%. Hair counts still improved compared with placebo. Lower exposure is not zero exposure. Sexual side effects are still possible with the spray, though less likely.
Man Matters' Minoxifin combines 0.1% finasteride with 5% minoxidil in an alcohol-free scalp solution. It is a different formula from the spray in that trial, so those results don't apply to it directly. Use it daily as directed on the pack, for at least six months, under a dermatologist's guidance. To compare it with plain minoxidil, read minoxidil vs minoxidil with finasteride.
Do You Need a Testosterone Test Before Finasteride?
Most men do not. Finasteride is chosen based on the type and stage of hair loss, not on hormone levels. A dermatologist may order blood tests if your hair loss looks unusual, or if you have other symptoms.
Tell your doctor you take finasteride before any prostate check or PSA blood test, so the result is read correctly.
When Should You See a Dermatologist?
See a dermatologist before you start finasteride, and again if any side effect bothers you. They can confirm that you have pattern hair loss and pick the right form of treatment.
Most men who ask about finasteride are young. In 7,04,152 Man Matters consultations (Aug 2025 to Aug 2026), 87.2% of hair fall consults came from men under 35.
On the Man Matters app, you can talk to a dermatologist. They check your family history, lifestyle, diet, sleep and a photo of your hairline. Then they confirm the cause and your stage of hair loss. Only then do they set the right treatment. When you buy minoxidil or finasteride from Man Matters, you get a free pass to talk to a dermatologist.
Hair loss is common, and it is normal to have questions about a hormone-related medicine. The men who see lasting change follow a plan built for their diagnosis. They use it as directed, keep up the basics, and stay with it for months.
Frequently Asked Questions
Will blocking DHT lower testosterone?
No. Blocking DHT means less testosterone is turned into DHT, so testosterone stays in the blood. In a 2004 trial of men with an enlarged prostate on 5 mg finasteride, testosterone stayed in the normal range and rose a little. DHT, the hormone linked to pattern hair loss, is what falls.
What are the dangers of taking finasteride?
The main concern is sexual side effects in a small share of men. These include lower sex drive or erection problems. A 2019 review of 15 trials found them about 1.66 times as often as with placebo. MedlinePlus also lists breast changes to report. Take it only on a doctor's prescription.
Can finasteride side effects on erections last after stopping?
They usually reverse after stopping, says the 2016 IADVL finasteride guideline. Some men report effects that continue after stopping, and the US label was updated in 2012 to mention this. A clear cause has not been established. If an erection problem lasts, see your doctor.