Finasteride for hair loss in San Diego
Finasteride is the most effective medical treatment available for male pattern hair loss, and it is also the one people have the most questions about. Both of those are true at once, and a page that only tells you the first half is not being straight with you.
It is a prescription medicine. It is prescribed after a consultation that establishes the diagnosis and goes through the side-effect profile properly — not as a formality at the end.
How it works
Male pattern hair loss is driven by dihydrotestosterone, or DHT — a more potent androgen the body makes from testosterone using an enzyme called 5-alpha reductase. In genetically susceptible follicles, DHT progressively shortens the growing phase and miniaturises the hair.
Finasteride inhibits that enzyme, substantially reducing DHT levels in the scalp and blood. Less DHT means slower miniaturisation, and in many men some recovery of follicles that had not yet been lost.
It works on the cause of pattern hair loss rather than on the hair cycle, which is what distinguishes it from minoxidil and why the two are often used together.
What to expect, and when
Nothing visible for the first three months. Reduced shedding and early improvement between three and six months. Peak effect at around twelve months.
The most important outcome is often the one that is hardest to see: hair that has not been lost. A year in which nothing appears to have changed is a good year in a progressive condition.
As with minoxidil, a temporary increase in shedding in the early weeks can occur as follicles cycle.
Side effects, discussed honestly
The commonly reported side effects are sexual: reduced libido, erectile difficulty and reduced ejaculate volume. In the randomised trials these occurred in a small percentage of men — low single figures — and in most cases resolved on stopping, and in a proportion of men resolved while continuing.
There are also reports of persistent symptoms after stopping, and of mood changes including depression. The literature on how common these are is genuinely contested. What is not contested is that they are reported, and anyone starting the medication should know that rather than hear it for the first time from a forum.
Breast tenderness or enlargement is uncommon but should be reported. Finasteride also lowers PSA readings by roughly half, which matters for prostate cancer screening — tell any doctor ordering a PSA that you take it.
If you develop side effects, stop and tell us. That is a routine conversation, not a failure.
⛔ Who must not take finasteride
It is contraindicated in women who are pregnant, may become pregnant, or are breastfeeding. Finasteride can cause abnormalities of the external genitalia in a male foetus, and this is not a theoretical concern — it is the reason the medicine carries the warning it does.
Women who may become pregnant should not handle crushed or broken tablets, because the active drug can be absorbed through the skin. Intact tablets are coated and are safe to handle.
It is not appropriate for anyone with a known hypersensitivity to finasteride or related medicines. Liver disease and a personal or family history of prostate cancer are reasons for a fuller discussion before prescribing rather than automatic exclusions.
What happens if you stop
The benefit is lost over roughly six to twelve months and the condition resumes its previous course. Finasteride suppresses the driver of pattern hair loss for as long as it is taken; it does not change the underlying susceptibility.
That is a long-term commitment, and it is worth deciding on deliberately at the start.
Questions about finasteride
How does finasteride stop hair loss?
It blocks 5-alpha reductase, the enzyme that converts testosterone into DHT. DHT is the hormone that progressively miniaturises hair follicles in men with a genetic susceptibility, so reducing it slows the process and in many men allows partial recovery of follicles not yet lost.
How long does finasteride take to work?
Nothing visible for around three months, early improvement between three and six months, and peak effect at about twelve months. In a progressive condition, hair that has not been lost is often the most important result.
What are the side effects of finasteride?
The commonly reported ones are sexual — reduced libido, erectile difficulty and reduced ejaculate volume — occurring in a small percentage of men in randomised trials and usually resolving on stopping. Persistent symptoms after stopping and mood changes including depression are also reported, and how common they are is genuinely contested in the literature. Breast tenderness is uncommon but should be reported.
Can women take finasteride for hair loss?
It is contraindicated in women who are pregnant, may become pregnant, or are breastfeeding, because it can cause abnormalities of the external genitalia in a male foetus. Women who may become pregnant should also not handle crushed or broken tablets. Any use in women is a specialist decision made individually.
Does finasteride affect PSA tests?
Yes. It lowers PSA readings by roughly half. Tell any doctor ordering a PSA test that you take finasteride, so the result is interpreted correctly.
What happens if I stop taking finasteride?
The benefit is lost over roughly six to twelve months and pattern hair loss resumes its previous course. The medicine suppresses the driver of the condition while it is taken; it does not change the underlying susceptibility.
Related treatments
Board-certified — American Board of Internal Medicine
Last reviewed August 8, 2026
You are quoted before anything begins.
Tell us what you're considering and we'll tell you honestly whether finasteride is the right treatment for it.