Finasteride side effects: an honest guide before you start
Finasteride works well for many men, but it has side effects you should know about from the outset. This guide explains how it works, what results to expect, what the EMA safety review concluded in 2025 and how to report a problem.
Most men do not get side effects from finasteride, but in a minority they are serious enough that you should know about them before you start. The main ones are changes in mood, including suicidal thoughts, and sexual problems such as reduced sex drive. If your mood changes, stop taking it and speak to a doctor. Our doctors can go through the risks, your history and the alternatives with you by video call, with no pressure.
Causes
Why does hair thin?
If you have noticed your temples receding or the top of your head looking thinner, you are not alone. Male pattern baldness is common and, in many men, starts around the age of twenty. It is not a medical emergency, but it can knock your confidence, and it is perfectly reasonable to want to do something about it.
It comes down mostly to two things: genetics and a hormone called DHT (dihydrotestosterone). If you have inherited hair follicles that are sensitive to it, DHT gradually shrinks them. Each new hair grows in a little finer and shorter than the last, until the follicle stops producing visible hair. That is why hair loss is usually gradual, at the temples, the crown or both.
Source: INFARMED, Infomed: finasteride 1 mg film-coated tablets (patient information leaflet).
How it works
Finasteride 1 mg: how it works and who it is for
Finasteride is one of the treatments you will hear about most. It works well for many men. It also has side effects that you deserve to know about at the start, not buried in small print. Here is the straightforward version, written by the doctors who would prescribe it.
Finasteride blocks the enzyme that turns testosterone into DHT. Less DHT means less pressure on the follicles, so hair loss slows and, in many men, some hair grows back.
In Portugal, the medicine information describes finasteride 1 mg as indicated for men aged 18 to 41 with early-stage androgenetic alopecia. (Online you will also find references to a 5 mg version: that is a different medicine, used for benign prostatic hyperplasia and not for hair.) Finasteride tablets are not indicated for women or for anyone under 18.
Sources: INFARMED, Infomed: finasteride 1 mg film-coated tablets (SmPC and patient information leaflet); INFARMED, Circular Informativa No. 056/CD/550.20.001.
What to expect
Finasteride before and after: what results to expect
It is a slow treatment, and patience is part of it. You take one tablet a day, with or without food. Most men do not notice much change in the first three to six months, and it is usually around a year before you can judge properly whether it is working.
It works best at keeping the hair you still have. Many men stop losing hair and some see visible regrowth, mainly on the crown. It is less likely to rebuild temples that have already receded a long way: the medicine information states that efficacy in bitemporal recession and in end-stage hair loss has not been established.
The finasteride before and after photos that circulate online show one person’s result and cannot predict yours. The person who can judge whether it is working in your case is the doctor who is following your treatment.
One thing many people do not know: it only works while you take it. If you stop, the hair you kept or regrew tends to be lost again over roughly the following year.
Source: INFARMED, Infomed: finasteride 1 mg film-coated tablets (SmPC and patient information leaflet).
Safety
Finasteride side effects, plainly
Most men who take finasteride have no problems. But a minority do, and some of those effects are serious enough that we want you to know about them before you decide, not afterwards. In official Portuguese documents they are called “efeitos indesejáveis” (undesirable effects); online, people searching for “finasterida efeitos colaterais” are looking for the same thing.
Your mood and mental health
In 2025, the European Medicines Agency (EMA) concluded a Europe-wide safety review of medicines containing finasteride and dutasteride. It confirmed suicidal thoughts as a side effect of finasteride tablets; warnings about mood changes, including depression, were already in the medicine information. It is not possible to say how often this happens (the EMA and INFARMED list the frequency as “not known”), but most cases were reported in men taking the 1 mg tablet for hair loss.
If you have ever had depression, anxiety or suicidal thoughts, tell us before you start. That does not automatically rule finasteride out, but it is an important part of the conversation.
Your sex life
A small number of men notice changes such as:
- reduced sex drive
- difficulty getting or keeping an erection
- changes in ejaculation, including less semen
In most men these effects go away when they stop taking the tablets. In some, however, they continued after treatment ended (more on this in the FAQ). The EMA and the medicine information also state that, in some patients, these sexual effects may contribute to changes in mood, including suicidal thoughts. So if something changes, speak to a doctor early. It is perfectly normal to raise, and you will not be the first to do so.
Breast changes
Some men have breast tenderness or enlargement. Breast cancer has also been reported in men taking finasteride. If you notice a lump, pain, swelling or any discharge from the nipple, seek medical assessment without delay.
Fertility
Infertility and poor semen quality have been reported in men who took finasteride, in some cases alongside other risk factors. Improvement has been reported after stopping. If you are trying for a baby with your partner, it is worth raising this first.
Less common effects
Some men have reported allergic reactions (rash, itching, hives or swelling of the lips, tongue or face), pain in the testicles, blood in the semen, palpitations or changes in liver blood tests. If you ever have difficulty breathing or swallowing, treat it as an emergency and get help straight away.
Sources: European Medicines Agency, review of finasteride and dutasteride; INFARMED, Circular Informativa No. 056/CD/550.20.001; INFARMED, Infomed: finasteride 1 mg film-coated tablets (SmPC and patient information leaflet).
In the box
The card that comes in the box
Following the EMA review, packs of finasteride 1 mg now include a small patient card. It summarises the risks of mood changes, including suicidal thoughts, and of sexual problems, and what to do if they occur. It is worth reading carefully, together with the leaflet, and keeping somewhere you can find it.
Sources: European Medicines Agency; EMA, Annex III (patient card text in Portuguese); INFARMED, Circular Informativa No. 056/CD/550.20.001.
Good to know
A few practical things worth knowing
- PSA tests: finasteride lowers the PSA value, a blood test used to assess the prostate. If you ever have one, tell the doctor that you take finasteride so that they can interpret the result correctly.
- If your partner is pregnant: finasteride can affect the development of a male baby. Women who are pregnant or who may become pregnant should not handle crushed or broken tablets. Whole tablets have a coating and can be touched.
- Donating blood: blood services have rules about some medicines, including, at times, a waiting period after you stop taking them. If you are a donor, tell the health professional who sees you that you take finasteride and follow their guidance.
- Topical options: the EMA review found no evidence linking suicidal thoughts to finasteride cutaneous spray. This conclusion concerns suicidal thoughts, and does not guarantee that a topical product has no side effects, but topical finasteride may be worth discussing, depending on your situation.
Sources: INFARMED, Infomed: finasteride 1 mg film-coated tablets; European Medicines Agency; IPST, “I am taking medicines. Can I give blood?”.
Your decision
So, is finasteride right for you?
Overall, the EMA concluded that the benefits of finasteride continue to outweigh its risks. But that is a judgement about large groups of people. Whether it makes sense for you depends on your health history, how much the hair loss bothers you and how you feel about the possible side effects. There is no wrong answer.
It is not the only option either. Topical minoxidil, topical finasteride, light therapy and hair transplantation all have their place, and some men simply prefer not to treat it. That is an equally valid choice.
Source: European Medicines Agency.
Minoxidil
Minoxidil and finasteride: two different medicines
Minoxidil and finasteride are not the same medicine. Minoxidil is applied to the scalp and, according to the information for a minoxidil product authorised in Portugal, the way it stimulates hair growth is not fully understood. Finasteride tablets work by reducing DHT.
Minoxidil also has its own precautions: the leaflet for that product states that it should not be used by people with high blood pressure or cardiovascular disease, or on a scalp with lesions or irritation. The medicine information also notes that corticosteroids and retinoids applied to the scalp may increase the effect or absorption of minoxidil. Whether it makes sense to use one, the other or both is something a doctor can weigh up once they know your history.
Source: INFARMED, Infomed: minoxidil 50 mg/ml cutaneous solution, SmPC and patient information leaflet.
Remote care
Talk to us about it
Our doctors can see you by video call, look at your hair loss, go through your medical and mental health history and help you weigh up the options, with no pressure.
If you decide to go ahead with finasteride, we will continue to follow you, including how you are feeling, and not only the state of your hair. Some cases need an in-person examination, and the doctor will tell you if yours is one of them.
Book a hair loss consultation to talk through the benefits, the side effects and the alternatives with one of our doctors.
Support
If you are going through a difficult time
Reporting
How to report side effects
If you think you are having a side effect, speak to your doctor or pharmacist. You can also report it directly to INFARMED, the National Authority of Medicines and Health Products, through the Portal RAM. The portal lets you report any suspected adverse reaction to a medicine, without an intermediary. If possible, have to hand the name and batch number of the medicine (shown on the packaging), the dose, the other medicines you take and a description of the effect. Reporting does not replace speaking to a doctor about your symptoms. Every report helps make medicines safer for the next person.
Care in Portugal
Talk to a doctor about hair loss
A video call lets you go through your hair loss, your medical and mental health history and the options, including the option of not treating it.
Thinking about finasteride? Speak to a doctor first.
Go through your hair loss, your history and the possible side effects with one of our doctors, by secure video call, with no pressure to start a treatment.
Sources
The evidence behind this article
Sources consulted on 24 October 2026.
The EMA review and the INFARMED circular cover both finasteride and dutasteride; this article deals with finasteride only. The INFARMED circular corresponds to the stage of the recommendation of the EMA’s pharmacovigilance committee (PRAC), in May 2025. The medicine information comes from a generic finasteride 1 mg authorised in Portugal and from a minoxidil product; other brands may differ. This article describes the risks and what a consultation can cover; any treatment decision is made by a doctor after an individual assessment.
Questions
Frequently asked questions about finasteride
Finasteride side effects: what are the main ones?
Most men have no problems. A minority notice changes in mood, including depression and suicidal thoughts (the frequency of suicidal thoughts is not known), or sexual effects, such as reduced sex drive, difficulty getting an erection and less semen. Breast tenderness or enlargement, allergic reactions and pain in the testicles have also been reported. If your mood changes, stop taking finasteride and speak to a doctor.
How long does finasteride take to show results?
Most men do not notice much change in the first three to six months, and it is usually around a year before you can judge properly whether it is working. It works best at keeping the hair you have, and it is less likely to rebuild temples that have already receded a long way.
Will the hair regrown with finasteride stay if I stop?
No. It only works while you take it. If you stop, the hair you kept or regrew tends to be lost again over roughly the following year.
What is “post-finasteride syndrome”?
It is a name used online for symptoms that continue after stopping finasteride. The information for the medicine authorised in Portugal that we consulted does not use that name, but it does list, among the reported undesirable effects, sexual problems that persist after stopping treatment (reduced sex drive, difficulty getting an erection and ejaculation problems), with frequency not known. If you notice symptoms like these, speak to a doctor early.
Is topical finasteride linked to suicidal thoughts?
The 2025 EMA review found no evidence linking suicidal thoughts to finasteride cutaneous spray, and INFARMED states that no new information was added for that formulation. This conclusion concerns suicidal thoughts only. Whether topical finasteride is right for you is something to discuss with a doctor.
Can I use minoxidil and finasteride together?
That decision belongs to a doctor who knows your history. They are different medicines, which work in different ways, and minoxidil has its own precautions: the leaflet for the product we consulted states that it should not be used by people with high blood pressure or cardiovascular disease.
