Finasteride Side Effects, Dose and Who Should Avoid It

Finasteride is a prescription medicine used to slow male pattern hair loss. It works by blocking the enzyme 5 alpha reductase, which reduces the conversion of testosterone into dihydrotestosterone, or DHT. DHT contributes to the gradual miniaturisation of susceptible hair follicles in male pattern hair loss.

For hair loss, the standard finasteride dose is 1 mg once daily. It can be taken with or without food, and benefit generally takes at least three months of daily treatment to become noticeable. Continued treatment is needed to maintain the effect.

Finasteride is not suitable for everyone. Sexual side effects such as reduced libido, erectile dysfunction and ejaculation problems are recognised adverse effects, and finasteride can also change PSA blood test results. Women who are pregnant or may become pregnant must not take finasteride, and they should not handle crushed or broken tablets because of the potential risk to a male fetus.

Understanding what finasteride does, what side effects to watch for and what needs to be monitored can help patients have a more informed discussion with their doctor before starting treatment.

What Does Finasteride Actually Do to Hair Loss?

Finasteride lowers DHT activity by inhibiting type II 5 alpha reductase. In men with androgenetic alopecia, this can slow further hair miniaturisation and help maintain existing hair.

It is mainly used for male pattern hair loss rather than every cause of hair shedding. If hair loss is caused by nutritional deficiency, thyroid disease, infection, inflammation, scarring or another condition, finasteride may not address the underlying problem.

This is why the diagnosis should come before the prescription.

Finasteride is also not established as a treatment for every area of recession. The prescribing information states that efficacy for bitemporal recession has not been established.

If you are considering medication for hair loss, you can read more about hair fall tablets explained as part of the wider medical treatment approach.

How Does Finasteride 1 mg Work?

Finasteride reduces the amount of DHT available to affect susceptible hair follicles.

The aim is generally to slow progression and preserve hair rather than produce an immediate cosmetic change.

The medicine does not work like a styling product or an instant growth treatment. Hair follicles need time to respond, so judging the result after only a few weeks can be misleading.

The official prescribing information states that daily use for three months or more is generally needed before benefit is observed. Continued use is recommended to maintain the benefit.

What Is the Standard Finasteride Dose?

For male pattern hair loss, the standard prescribed dose is:

Finasteride 1 mg once daily.

It may be taken with or without food. Taking more than the prescribed amount does not make the treatment work faster.

A missed dose should not normally be replaced by taking extra tablets. The patient should follow the prescribing instructions provided by the doctor or pharmacist.

Finasteride is a prescription medicine, so the appropriate dose and suitability should be assessed for the individual patient.

How Long Does Finasteride Take to Work?

Finasteride does not produce an immediate change in hair density.

The official product information states that three months or more of daily treatment may be necessary before benefit is observed. Continued use is needed to maintain the effect.

Some patients may notice changes earlier or later, but hair treatment should generally be assessed over months rather than days.

Progress photographs taken under similar lighting and from similar angles can be more useful than checking the mirror every day.

For more information about treatment timelines, see how long hair fall medicines take to work.

How Common Are Finasteride Side Effects Really?

Finasteride can cause side effects, but they do not affect every person who takes it.

The recognised sexual adverse effects include:

• Decreased libido
• Erectile dysfunction
• Ejaculation disorder, including reduced ejaculate volume

These are among the most common adverse reactions identified in the prescribing information.

Other reported effects include breast tenderness or enlargement, testicular pain, mood related symptoms and allergic reactions. Breast changes such as a lump, pain or nipple discharge should be reported promptly to a healthcare professional.

The important point is that a patient should know about possible adverse effects before starting treatment rather than discovering them unexpectedly.

Do Finasteride Side Effects Reverse If You Stop?

Sexual adverse effects reported during clinical studies often resolved in men who stopped treatment, and many also resolved while treatment continued.

However, patients should not assume that every symptom will automatically disappear immediately after stopping.

There have also been post marketing reports of sexual dysfunction continuing after discontinuation. Because individual experiences vary, persistent or troublesome symptoms should be discussed with a doctor rather than ignored.

Stopping or changing prescribed treatment should be discussed with the prescribing clinician, particularly when finasteride is being used as part of a broader hair loss plan.

Can Finasteride Affect Fertility?

Fertility is an important question for men considering finasteride.

Finasteride can affect semen parameters in some men, and the product information includes effects on ejaculation and semen volume among recognised adverse effects. The effect on fertility can vary between individuals.

A man who is actively trying to conceive, has an existing fertility problem or notices a change in sexual or reproductive function should discuss this with his doctor before deciding whether to continue treatment.

The decision should be individual rather than based on a general assumption that finasteride either always causes infertility or never affects fertility.

Who Should Not Take Finasteride?

Finasteride 1 mg is indicated for the treatment of male pattern hair loss in men and is not indicated for women or children. It is contraindicated during pregnancy.

Particular caution is required around pregnancy because finasteride can affect the development of the external genitalia of a male fetus.

Women who are pregnant or may become pregnant should not handle crushed or broken finasteride tablets. The tablets are coated, so normal handling of intact tablets does not present the same exposure concern, but broken or crushed tablets should be avoided.

Anyone with a known hypersensitivity to finasteride or its ingredients should also not take it.

Children should not use finasteride for hair loss.

A doctor should also review the patient’s medical history and other medicines before prescribing it.

Can Women Take Finasteride for Hair Loss?

Finasteride 1 mg for male pattern hair loss is not indicated for women. In particular, women who are pregnant or may become pregnant must not take it because of the potential risk to a male fetus.

Hair loss in women has many possible causes, including female pattern hair loss, postpartum shedding, thyroid disorders, nutritional problems and other medical conditions.

A woman experiencing significant hair loss should therefore have the cause assessed rather than using finasteride without medical advice.

Does Finasteride Affect a PSA Test?

Yes.

Finasteride lowers serum PSA levels, which can affect interpretation of PSA testing. In clinical studies of finasteride 1 mg in men aged 18 to 41, the mean PSA value decreased from 0.7 ng/mL to 0.5 ng/mL after 12 months.

This does not mean PSA testing cannot be performed.

It means the doctor interpreting the result needs to know that the patient is taking finasteride.

Any confirmed increase from the lowest PSA value while taking finasteride should be medically evaluated, even if the result remains within a range that might otherwise appear normal.

For this reason, always tell the doctor ordering a PSA test that you are taking finasteride.

What Should Be Monitored While You Are on Finasteride?

Finasteride does not require the same routine blood monitoring for every patient as some other medicines. Monitoring is instead based on the patient’s symptoms, treatment response, medical history and any relevant tests.

PSA becomes particularly important when a patient undergoes prostate assessment.

The following table provides a practical framework for discussing follow up with the prescribing doctor.

Finasteride Monitoring Table

Time	What is assessed	What test if any	Finding that may mean stopping or urgently reviewing treatment
Before starting	Diagnosis, hair loss pattern, medical history, medicines, sexual and reproductive concerns	Tests only when clinically indicated; baseline PSA may be relevant depending on age and prostate assessment	Pregnancy, known allergy, unsuitable diagnosis or an important medical contraindication
Month 3	Early response, tolerance and side effects	Usually clinical review; tests only if indicated	Troublesome sexual effects, allergic reaction, significant mood symptoms or another concerning adverse effect
Month 6	Hair loss progression, response and adverse effects	PSA if clinically indicated	Persistent or significant adverse effects or an unexpected clinical finding
Month 12	Long term response and treatment tolerance	PSA interpretation where relevant	Significant ongoing adverse effects or another finding requiring treatment reassessment
Yearly	Continued need, hair response, side effects and other health changes	Tests according to age, symptoms and medical need	New contraindication, significant adverse effects or another reason the doctor advises changing treatment

This is a general framework rather than a fixed monitoring schedule for every patient. The appropriate follow up depends on age, health history, symptoms and the reason finasteride was prescribed.

What Happens If You Stop Finasteride?

Finasteride works only while treatment is maintained.

The prescribing information states that withdrawal of treatment leads to reversal of the treatment effect within 12 months.

This means stopping treatment can allow the underlying male pattern hair loss process to continue.

It is therefore important to distinguish between stopping because of a temporary concern and stopping because of a confirmed adverse effect or medical reason.

If you are considering stopping finasteride, discuss the decision with your doctor so that another hair loss strategy can be considered where appropriate.

Finasteride and Long Term Hair Loss Planning

Finasteride is one part of medical treatment for male pattern hair loss.

The appropriate plan depends on the stage and pattern of hair loss, age, donor supply, family history, response to treatment and personal priorities.

Some patients may use medication to slow progression before considering other procedures. Others may continue medical treatment alongside a surgical hair restoration plan when appropriate.

You can also review hair transplant medicines to understand how medication fits into a broader hair restoration approach.

The important point is that a hair transplant does not stop the underlying progression of untreated male pattern hair loss. Long term planning may therefore include medical treatment where appropriate.

When Should You Discuss Finasteride With a Doctor?

A consultation is particularly useful when hair loss is progressing quickly, the diagnosis is uncertain, there are scalp symptoms, there is a significant medical history, fertility is a concern or the patient is unsure about potential adverse effects.

A doctor can assess whether the pattern is consistent with male pattern hair loss and whether finasteride is an appropriate option.

The discussion should include expected benefits, possible side effects, dose, treatment duration and what should happen if the medicine is not tolerated.

Frequently Asked Questions

Finasteride is one of several medicines that may be considered for male pattern hair loss. Before starting treatment, it is useful to understand the different types of hair fall tablets explained, how they work, and why the right medicine depends on the cause and pattern of hair loss.

Hair loss medicines do not produce an immediate change. Some treatments require several months of consistent use before their effect can be assessed. Understanding how long hair fall medicines take to work can help set realistic expectations and avoid stopping treatment too early.

Medication may also be discussed alongside other hair restoration options when appropriate. The overall treatment plan can depend on the stage of hair loss, donor hair availability and whether the patient may eventually consider surgery. More information about hair transplant medicines can help explain how medical treatment fits into a longer term hair restoration plan.

Because finasteride is a prescription medicine with specific precautions, the decision to start, continue or stop it should be discussed with a qualified doctor. If you have questions about side effects, fertility, PSA testing or whether the medicine is appropriate for you, you can discuss medicines with the doctor before making a treatment decision.