Finasteride Side Effects: What They Are and How Common Are They Really?

If you've been researching finasteride for hair loss, you've probably come across two very different stories.

One says finasteride is one of the most effective treatments for male pattern hair loss.

The other focuses on finasteride side effects, particularly sexual dysfunction, reduced libido, erectile dysfunction and possible psychological effects.

So what is actually true?

Are finasteride side effects common?

Can finasteride cause erectile dysfunction?

Can finasteride affect your sex drive?

Can side effects continue after stopping?

And perhaps most importantly:

Is finasteride safe enough to consider for hair loss?

The answer requires a little more nuance than a simple yes or no.

Finasteride is an established prescription medicine for male pattern hair loss, but it can cause adverse effects in some men. The official UK product information reports sexual adverse effects more frequently with finasteride than placebo during the first year, although the absolute percentages were relatively low and discontinuation because of drug-related sexual effects was approximately 1% in both groups.

At the same time, the UK's Medicines and Healthcare products Regulatory Agency (MHRA) has strengthened its warnings about psychiatric side effects and sexual dysfunction, meaning these risks should be taken seriously and discussed before treatment.

This article explains what we know about finasteride side effects, how common they are, what the latest UK safety advice says and what you should consider before starting treatment.

What Is Finasteride?

Finasteride is a prescription medicine used to treat male pattern hair loss, also known as androgenetic alopecia.

For hair loss, the usual licensed dose is 1 mg once daily.

Finasteride works by inhibiting an enzyme called 5-alpha reductase.

This reduces the conversion of testosterone into dihydrotestosterone (DHT).

DHT is an important factor in male pattern hair loss because genetically susceptible hair follicles can become progressively smaller under its influence.

Over time, this can result in:

• A receding hairline
• Thinning temples
• Crown thinning
• Reduced hair density
• Finer hair
• Progressive male pattern baldness

By reducing DHT, finasteride can help slow this process and support the preservation of existing hair.

However, because finasteride changes the hormonal pathway involved in DHT production, it is understandable that people have questions about its effects beyond the scalp.

That is where finasteride side effects become particularly important.

How Common Are Finasteride Side Effects?

This is probably the most important question in this article.

The UK Summary of Product Characteristics for finasteride 1 mg reports safety data from clinical studies involving more than 3,200 men with male pattern hair loss. In three 12-month, placebo-controlled studies, the overall safety profiles of finasteride and placebo were similar.

During the first 12 months, drug-related sexual adverse effects were reported in:

3.8% of men taking finasteride

compared with:

2.1% of men taking placebo.

The product information also reports that approximately 1% of men in each group discontinued treatment because of drug-related sexual adverse effects during the first year.

This is an important distinction.

It means sexual side effects were reported more frequently with finasteride than placebo, but they were still experienced by a minority of participants.

It also demonstrates why simply saying "finasteride causes sexual dysfunction" without explaining the numbers can give an incomplete picture.

What Are the Most Common Finasteride Side Effects?

The most discussed adverse effects involve sexual function.

These include:

• Reduced libido
• Erectile dysfunction
• Ejaculation disorders
• Reduced volume of ejaculate

Does Finasteride Cause Erectile Dysfunction?

This is one of the biggest concerns people have when researching finasteride side effects.

The answer is:

Erectile dysfunction has been reported as an adverse effect of finasteride.

In the clinical trials described in the UK product information, erectile dysfunction was reported in 1.3% of men taking finasteride compared with 0.7% taking placebo during the relevant 12-month period.

That means erectile dysfunction was reported in both groups, but more frequently among men taking finasteride.

It is therefore not accurate to say that finasteride never causes erectile dysfunction.

Equally, it would be misleading to suggest that erectile dysfunction is inevitable.

For most men in these trials, it was not reported.

Does Finasteride Lower Libido?

It can.

Reduced libido is one of the recognised sexual adverse effects associated with finasteride.

In clinical trials, decreased libido was reported in:

1.8% of men taking finasteride

compared with:

1.3% of men taking placebo.

The difference between the groups was relatively small, but it was enough for reduced libido to be recognised as an adverse effect.

If you notice a significant change in your sex drive after starting finasteride, you should discuss it with your prescriber.

Does Finasteride Cause Ejaculation Problems?

Finasteride can affect ejaculation in some men.

The product information lists ejaculation disorders, including decreased volume of ejaculate, among the recognised adverse effects.

In the clinical trials, decreased ejaculate volume was reported in 0.8% of finasteride-treated men compared with 0.4% of placebo-treated men.

Again, this was not common, but it is a recognised potential side effect.

Can Finasteride Cause Depression?

This is an area where it is particularly important to distinguish between older clinical-trial data and more recent safety monitoring.

Depression has been reported in people taking finasteride.

The MHRA states that finasteride is associated with depression and suicidal ideation, as well as sexual dysfunction.

The UK product information also lists depression as an adverse reaction and suicidal ideation as a reaction reported through post-marketing surveillance.

The MHRA strengthened its safety warnings in May 2026 following a review of available evidence.

For patients prescribed finasteride 1 mg, the MHRA advises stopping treatment if depression or suicidal thoughts develop and contacting a healthcare professional as soon as possible.

This is an important safety message that should not be overlooked.

Can Finasteride Cause Suicidal Thoughts?

The MHRA has specifically warned about the association between finasteride and suicidal thoughts and behaviours.

This does not mean that everyone taking finasteride will experience these symptoms.

However, because of the potential seriousness of the risk, the MHRA recommends that healthcare professionals consider a patient's history of depression or suicidal ideation before prescribing and monitor patients for psychiatric symptoms.

If someone taking finasteride develops depression or suicidal thoughts, the MHRA advises patients taking the 1 mg formulation for hair loss to stop the medicine and contact their healthcare professional as soon as possible.

If you feel at immediate risk of harming yourself, seek emergency medical help.

Can Finasteride Cause Anxiety?

Anxiety has been reported during post-marketing use of finasteride, although the frequency cannot be reliably estimated from spontaneous reports.

This is an important example of why the phrase "finasteride side effects percentage" can be difficult to answer for every possible adverse effect.

Some side effects are measured systematically in controlled clinical trials.

Others are identified through post-marketing surveillance.

For spontaneously reported adverse effects, regulators cannot calculate a reliable incidence rate because there is no defined denominator representing everyone who has taken the medicine.

Can Finasteride Cause Permanent Side Effects?

This is one of the most searched questions surrounding finasteride.

There have been reports of persistent sexual dysfunction after discontinuation of finasteride.

The UK product information specifically states that persistent sexual dysfunction, including decreased libido, erectile dysfunction and ejaculation disorders, has been reported after stopping finasteride.

The MHRA has also highlighted that sexual dysfunction may persist after treatment is stopped.

This means it would be inappropriate for a healthcare website to tell patients that all finasteride side effects definitely disappear immediately after stopping.

At the same time, persistent symptoms appear to be different from the typical short-term adverse effects observed in clinical trials, and the exact frequency and mechanism of persistent symptoms remain difficult to quantify.

The safest approach is to acknowledge the risk rather than dismiss it.

Do Finasteride Side Effects Go Away?

Often, adverse effects can resolve.

The UK product information states that sexual side effects resolved in men who discontinued treatment and in many men who continued treatment.

Interestingly, the incidence of the reported sexual adverse effects decreased over longer-term treatment.

The product information reports that drug-related sexual adverse effects fell from 3.8% during the first 12 months to 0.6% over the following four years in finasteride-treated men.

By the fifth year of treatment, the proportion of men reporting each of the specific sexual side effects listed in the clinical-trial data had fallen to below 0.3%.

However, this does not negate the post-marketing reports of persistent sexual dysfunction.

Both pieces of information need to be considered when discussing finasteride safety.

How Many Men Stop Finasteride Because of Side Effects?

This is another useful way to understand how common clinically significant side effects are.

In the three 12-month placebo-controlled trials, discontinuation due to any clinical adverse experience occurred in:

• 1.7% of finasteride-treated men
• 2.1% of placebo-treated men

Approximately 1% of men in each treatment group discontinued specifically because of drug-related sexual adverse effects during the first year.

This suggests that although side effects can occur, they did not lead to treatment discontinuation for the majority of participants in those clinical trials.

If SynovaMed's own verified patient data shows that 98.6% of patients remained on treatment, that can be included separately as a SynovaMed outcome statistic, provided the underlying dataset and definition of "remained on treatment" are documented.

Is Finasteride Safe?

There isn't a responsible medical answer that simply says "finasteride is completely safe."

No prescription medicine is completely risk-free.

Finasteride has a well-established clinical use for male pattern hair loss, and clinical trials have demonstrated a generally similar overall safety profile to placebo.

However, recognised risks include:

• Reduced libido
• Erectile dysfunction
• Ejaculation disorders
• Depression
• Suicidal ideation
• Anxiety
• Persistent sexual dysfunction in post-marketing reports
• Other less common or frequency-unknown adverse effects

The MHRA's updated 2026 warnings reinforce the importance of discussing psychiatric and sexual side effects before treatment.

Therefore, the better question isn't simply:

"Is finasteride safe?"

It is:

"Is finasteride appropriate for me, given my medical history and the potential benefits and risks?"

That is exactly why prescription treatment should involve clinical assessment.

Finasteride Side Effects vs Benefits

When considering any medicine, the potential benefits need to be weighed against the potential risks.

For male pattern hair loss, the potential benefits of finasteride include:

• Slowing further hair loss
• Preserving existing hair
• Improving hair density in some men
• Supporting long-term hair maintenance
• Potentially improving the appearance of thinning

The potential risks include the adverse effects discussed above.

There is therefore no universal answer to whether finasteride is "worth it".

For one person, the potential benefit of slowing progressive hair loss may outweigh the potential risks.

For another person, particularly someone with relevant medical or psychiatric history, another approach may be more appropriate.

Finasteride and Sexual Function: What Does the Evidence Say?

Sexual side effects are probably the most controversial aspect of finasteride treatment.

The controlled clinical-trial data provide useful numbers.

During the first 12 months:

• Drug-related sexual adverse effects: 3.8% vs 2.1% with placebo
• Decreased libido: 1.8% vs 1.3%
• Erectile dysfunction: 1.3% vs 0.7%
• Decreased ejaculate volume: 0.8% vs 0.4%

But these figures shouldn't be interpreted as proving that finasteride has no meaningful sexual risk.

Post-marketing surveillance has identified reports of persistent sexual dysfunction after discontinuation, and the MHRA has specifically strengthened warnings about sexual dysfunction.

The most accurate conclusion is therefore:

Sexual side effects are recognised but were uncommon in controlled clinical trials, while persistent sexual dysfunction has also been reported after treatment and requires appropriate counselling.

Does Finasteride Affect Testosterone?

Finasteride does not work by simply "lowering testosterone".

Its primary action is to inhibit 5-alpha reductase, reducing the conversion of testosterone to DHT.

This means that the main hormonal change is a reduction in DHT rather than the elimination of testosterone.

This distinction matters because online discussions about finasteride sometimes describe it inaccurately as a testosterone-lowering medicine.

If you're concerned about hormonal effects, discuss your individual circumstances with your clinician.

Does Finasteride Affect Fertility?

Fertility is another area where patients often have concerns.

The UK product information notes that long-term human data on fertility are limited and that spontaneous reports of infertility and/or poor seminal quality have been received after marketing. It also notes that some reported patients had other factors that could have contributed and that improvement or normalisation of semen quality has been reported after discontinuation.

If you're actively trying to conceive, have fertility concerns or have previously experienced abnormal semen results, tell your prescriber before starting finasteride.

This is particularly important because your personal circumstances may change the balance between the potential benefits and risks of treatment.

Finasteride Side Effects and Long-Term Use

Finasteride is generally intended as a long-term treatment for male pattern hair loss.

The UK product information states that continuous use is recommended to sustain the benefit. If treatment is stopped, beneficial effects begin to reverse after approximately six months and return towards baseline by around nine to 12 months.

Long-term clinical data have also demonstrated sustained hair-loss stabilisation in men who continued treatment.

This means that deciding whether to start finasteride isn't just about the first few weeks.

You should consider whether you're comfortable with a long-term treatment strategy and whether the potential benefits justify the potential risks for you.

What Happens If You Experience Finasteride Side Effects?

Don't simply ignore significant symptoms.

If you experience:

• Persistent erectile dysfunction
• A significant reduction in libido
• Ejaculation problems
• Mood changes
• Depression
• Anxiety
• Suicidal thoughts

you should contact your healthcare professional.

The MHRA specifically advises patients taking finasteride to seek medical advice if they experience sexual dysfunction. For finasteride 1 mg, patients who develop depression or suicidal thoughts are advised to stop treatment and contact their healthcare professional as soon as possible.

If you experience suicidal thoughts or feel you are at immediate risk of harming yourself, seek urgent medical help.

Should You Stop Finasteride If You Have Side Effects?

This depends on the nature and severity of the symptoms.

For psychiatric symptoms, the MHRA provides specific advice for people taking finasteride 1 mg for hair loss.

For sexual side effects, the MHRA advises contacting your healthcare professional.

Your prescriber can help determine whether the symptoms could be related to finasteride and what the most appropriate next step is.

Do not make decisions about prescription treatment based solely on social media posts, forums or anecdotal experiences.

Finasteride Side Effects Compared With Minoxidil Side Effects

If you're worried about finasteride, you may be wondering whether minoxidil is a better option.

The medicines have different mechanisms and different side-effect profiles.

Finasteride

Potential concerns include:

• Sexual dysfunction
• Reduced libido
• Erectile dysfunction
• Ejaculation disorders
• Depression
• Suicidal thoughts
• Persistent sexual dysfunction reported after discontinuation

Minoxidil

Topical minoxidil is more commonly associated with local effects such as:

• Scalp irritation
• Dryness
• Itching
• Redness
• Flaking
• Unwanted facial hair

The right treatment isn't necessarily the one with the shortest list of side effects.

It is the one that is appropriate for your diagnosis, medical history and treatment goals.

What About Finasteride and Minoxidil Together?

Some men use finasteride and minoxidil together because the medicines work differently.

Finasteride targets the DHT pathway.

Minoxidil acts directly at the hair follicle and supports the hair-growth cycle.

Research into combination treatment has produced encouraging results.

A 2024 randomised study found topical finasteride 0.25% combined with topical minoxidil 5% produced a higher efficacy rate than minoxidil 5% alone after 12 weeks.

Other randomised studies have also reported greater improvements in hair-density measures with combination treatment than with individual treatments in men with androgenetic alopecia.

However, it is important not to assume that every combination, formulation or dose has identical evidence.

For example, oral finasteride plus oral minoxidil is not the same regimen as topical finasteride plus topical minoxidil.

If you're considering combination treatment, it should be discussed with a qualified prescriber.

You can learn more about hair loss treatment for men through SynovaMed's Men's Health service.

Is Finasteride Worth the Risk?

This is perhaps the most personal question.

Finasteride has a genuine potential benefit for men with androgenetic alopecia.

It can slow hair loss and help preserve hair.

But it also has genuine potential risks.

The decision should therefore involve a balanced assessment of:

Your degree of hair loss

Your treatment goals

Your medical history

Your mental health history

Your sexual health

Your fertility plans

Your attitude towards potential side effects

Your willingness to continue treatment long term

A good clinical consultation should give you enough information to make an informed decision.

How SynovaMed Approaches Finasteride Treatment

At SynovaMed, prescription hair-loss treatment is approached as a clinical decision rather than simply an online purchase.

Through the Men's Health service, eligible patients can undergo an online consultation where relevant medical information is assessed before treatment is prescribed.

This allows the prescriber to consider:

• Your hair-loss pattern
• Your medical history
• Current medicines
• Previous treatments
• Potential contraindications
• Psychiatric history
• Sexual health considerations
• Your treatment objectives

If treatment is clinically appropriate, the prescriber can recommend a suitable option.

This may include finasteride, minoxidil or a combination approach depending on the individual's circumstances.

What Does the 98.6% Figure Mean?

If you're using SynovaMed's 98.6% treatment continuation statistic, this can be a useful trust signal, but it needs to be presented accurately.

For example:

98.6% of SynovaMed patients remained on treatment according to our internal patient outcome data.

However, it should not be presented as meaning:

"Only 1.4% experienced side effects."

Those are completely different measurements.

A patient may discontinue treatment for many reasons unrelated to side effects.

Likewise, remaining on treatment doesn't necessarily mean that a patient experienced no adverse effects.

If you publish this statistic, consider adding a methodology note explaining:

• The number of patients included
• The period measured
• What "remained on treatment" means
• Whether patients were actively followed up
• The treatment regimen
• The follow-up period

That makes the claim considerably more credible.

Frequently Asked Questions About Finasteride Side Effects

What are the most common side effects of finasteride?

The main recognised side effects include reduced libido, erectile dysfunction and ejaculation disorders. In clinical trials, drug-related sexual adverse effects occurred in 3.8% of finasteride-treated men compared with 2.1% receiving placebo during the first year.

How common is erectile dysfunction with finasteride?

In the clinical-trial data in the UK product information, erectile dysfunction was reported in 1.3% of men taking finasteride compared with 0.7% taking placebo.

Does finasteride cause low libido?

Reduced libido is a recognised side effect. It was reported in 1.8% of finasteride-treated men compared with 1.3% taking placebo in the relevant clinical-trial data.

Can finasteride cause depression?

Depression has been reported with finasteride, and the MHRA now specifically warns about psychiatric side effects including depression and suicidal ideation.

Can finasteride cause suicidal thoughts?

The MHRA has warned about suicidal thoughts and behaviours associated with finasteride. Patients taking 1 mg for hair loss who develop depression or suicidal thoughts are advised to stop treatment and contact their healthcare professional as soon as possible.

Can finasteride side effects continue after stopping?

Persistent sexual dysfunction has been reported after discontinuation of finasteride. The MHRA specifically warns that sexual dysfunction may persist after treatment is stopped.

Are finasteride side effects permanent?

Persistent sexual dysfunction has been reported, but it would be inaccurate to say that finasteride side effects are always permanent. Clinical-trial data also show that sexual side effects resolved in many men who continued treatment or stopped treatment.

Does finasteride affect fertility?

Reports of infertility and poor seminal quality have been received after marketing. The UK product information notes that long-term human fertility data are limited and that improvement in semen quality has been reported after discontinuation.

Is finasteride safe for long-term use?

Finasteride has long-term clinical data supporting its use for male pattern hair loss, but no prescription medicine is completely risk-free. Long-term treatment should be reviewed with a healthcare professional, particularly if you develop side effects.

Is finasteride worth taking for hair loss?

That depends on your individual circumstances. Finasteride can be effective at slowing male pattern hair loss, but its potential benefits need to be weighed against its potential adverse effects.

Can I take finasteride and minoxidil together?

Finasteride and minoxidil can be used together in appropriate patients. Research suggests that some combination regimens may provide greater improvements than individual treatments, but the specific formulation and route of administration matter.

Final Takeaway: How Worried Should You Be About Finasteride Side Effects?

Finasteride side effects deserve to be taken seriously.

But they also need to be understood in context.

In controlled clinical trials of finasteride 1 mg for male pattern hair loss, sexual adverse effects were reported in a minority of men, with drug-related sexual adverse effects occurring in 3.8% compared with 2.1% with placebo during the first year.

At the same time, the MHRA has strengthened UK safety warnings regarding depression, suicidal ideation and sexual dysfunction, including the possibility that sexual dysfunction may persist after treatment is stopped.

So the right message isn't:

"Finasteride is completely safe."

Nor is it:

"Finasteride will ruin your sex life."

The evidence supports a more balanced conclusion:

Finasteride can be an effective treatment for male pattern hair loss, but it has recognised risks and isn't suitable for everyone.

If you're considering finasteride, the safest approach is to have your medical history and individual circumstances assessed before starting treatment.

If you're experiencing hair thinning, a receding hairline or crown hair loss, you can explore SynovaMed's Prescription Hair Loss Treatment through its Men's Health service.

Medical Disclaimer

This article is for general educational purposes and does not replace individual medical advice, diagnosis or treatment.

Finasteride is a prescription-only medicine and is not suitable for everyone. Treatment should only be started following appropriate clinical assessment and according to the instructions provided by your prescriber.

The MHRA has issued updated safety warnings concerning finasteride and psychiatric side effects, including depression and suicidal ideation, as well as sexual dysfunction. Patients taking finasteride 1 mg for hair loss who develop depression or suicidal thoughts are advised to stop treatment and contact their healthcare professional as soon as possible.

If you experience suicidal thoughts or believe you are at immediate risk of harming yourself, seek urgent medical assistance.