If you are researching male pattern hair loss, you may have come across finasteride. You may also see it, along with dutasteride, mentioned in treatments for an enlarged prostate because both medicines reduce dihydrotestosterone (DHT). DHT contributes to scalp hair follicle miniaturisation and also plays a role in prostate tissue growth.
You should know that finasteride and dutasteride are not interchangeable. In the UK, finasteride 1 mg is licensed for male pattern hair loss, while higher-dose finasteride and dutasteride are licensed for benign prostatic hyperplasia (BPH). You can discuss whether dutasteride is appropriate for you as an off-label hair loss treatment, including the dose, monitoring and possible side effects.
How Finasteride and Dutasteride Work Differently
Finasteride and dutasteride are 5-alpha-reductase inhibitors that reduce the conversion of testosterone into dihydrotestosterone (DHT). If you are taking finasteride, it mainly blocks type II 5-alpha-reductase, while dutasteride blocks both type I and type II, producing a greater reduction in DHT.
These medicines do not remove testosterone from your body; instead, they reduce how much is converted into DHT. You may see them used for hair loss or benign prostate enlargement, but they are not the same as androgen deprivation therapy (ADT) used for prostate cancer. You should therefore discuss the specific medicine and its licensed use with your doctor.
Why DHT Matters for Both Your Hair and Prostate
Dihydrotestosterone (DHT) is made when testosterone is converted by an enzyme called 5-alpha-reductase. You may respond differently to DHT depending on your genetics and how sensitive your tissues are to androgen signals. DHT affects several tissues, including the prostate, scalp and body hair, so you may notice its effects in different ways.
In the scalp, reducing DHT can slow hair follicle miniaturisation if you have androgenetic alopecia. In the prostate, lowering DHT can gradually reduce prostate volume and help manage benign prostate enlargement in selected men. You can therefore see why DHT matters if you are considering finasteride, as the same hormonal pathway can be relevant to both hair loss and prostate health. You should discuss how this applies to you with your doctor.
How Does DHT Cause Male Pattern Hair Loss?
Male pattern hair loss, or androgenetic alopecia, develops through a combination of genetics and DHT activity. If you have follicles that are sensitive to DHT, you may notice them gradually becoming smaller and producing shorter, finer and lighter hairs. Over time, you can see thinning at the temples, front or crown, while the sides and back are usually less affected.
Finasteride works by reducing DHT rather than creating new hair follicles. If you have follicles that are still producing hair, lowering DHT may help slow further miniaturisation and preserve existing growth. You may therefore benefit more when treatment is started before hair loss becomes very advanced, although your response can vary.
Why Lowering DHT Can Help an Enlarged Prostate
The prostate responds strongly to DHT, which helps maintain prostate tissue. As you get older, prostate enlargement can press on the urethra, causing a weaker urine stream, difficulty starting, frequent urination or getting up at night.
5-alpha-reductase inhibitors lower DHT and can gradually shrink an enlarged prostate in suitable men. These medicines work gradually, so it may take several months before their full effect becomes noticeable.
Why Is Finasteride Used at Different Doses for Hair and Prostate Problems?
Finasteride is available in different doses because it is licensed for different conditions. In the UK, 1 mg is used for male pattern hair loss, while 5 mg is used for benign prostate enlargement to reduce prostate size and improve urinary symptoms.
You should not assume that a higher dose will give you better hair growth, as there is no evidence that increasing the 1 mg dose improves its effectiveness for hair loss. If you are taking finasteride for your prostate and are concerned about hair loss, speak to your doctor or dermatologist before changing your dose.
Evidence Note
Finasteride 1 mg once daily is the licensed dose for male pattern hair loss in men, and increasing the dose has not been shown to improve effectiveness. Finasteride 5 mg is used for benign prostatic enlargement, so the higher dose should not be viewed as a stronger hair-loss treatment.
How Is Dutasteride Different From Finasteride?
Finasteride mainly blocks type II 5-alpha-reductase, while dutasteride blocks both type I and type II. This means dutasteride suppresses DHT more strongly. You may therefore see a greater reduction in DHT with dutasteride, although that does not automatically make it the right choice for you.
Dutasteride also stays in your body much longer, with a half-life of around three to five weeks. You should discuss the reason for treatment, your medical history and potential side effects with your doctor before changing medicines.
How Do Finasteride and Dutasteride Compare?
| Feature | Finasteride | Dutasteride |
| 5-alpha-reductase action | Mainly inhibits type II | Inhibits type I and type II |
| UK hair-loss licence | 1 mg licensed for male pattern hair loss in men | Not licensed for hair loss |
| UK prostate licence | 5 mg licensed for BPH | 0.5 mg licensed for BPH |
| Hair-loss use | Standard licensed oral option in suitable men | Off-label |
| DHT suppression | Substantial | Greater systemic DHT suppression |
| Time in the body | Shorter | Much longer; half-life around 3–5 weeks |
| PSA | Can reduce PSA; effect differs between 1 mg and 5 mg use | Mean PSA falls around 50% after about 6 months |
| Important safety issues | Sexual dysfunction and psychiatric effects, including depression and suicidal thoughts | Sexual/reproductive effects and precautionary psychiatric safety considerations |
How Does Finasteride Help Male Pattern Hair Loss?
Finasteride lowers DHT and can slow the follicle miniaturisation that drives male pattern hair loss. You may first notice that hair loss slows or stabilises before you see thicker hair or improved density. The response is gradual, so you should not expect noticeable results within just a few weeks.
You may need around three to six months before early benefits become clear, and photographs can help you track subtle changes. If finasteride works for you, continued treatment is generally needed to maintain its effect, as stopping it allows the underlying hair-loss process to resume.
Is Dutasteride Used for Hair Loss?
Dutasteride lowers DHT and has been studied for male pattern hair loss, but in the UK it is licensed for benign prostate enlargement, not hair loss. If you are considering it for hair loss, you should know that this would be an off-label use.
Some studies suggest dutasteride may improve hair counts more than finasteride, but stronger DHT suppression does not automatically mean better results for you. You should discuss the potential benefits, risks and alternatives with your dermatologist before considering treatment.
Research Insight
A systematic review and meta-analysis of three comparative studies involving 576 men found that dutasteride produced greater improvements in several hair-growth measures than finasteride over 24 weeks. However, the evidence base was relatively small and dutasteride remains an off-label treatment for male pattern hair loss in the UK.
How Long Do Hair-Loss Treatments Need to Be Taken?
Male pattern hair loss is a long-term condition, so finasteride is generally used continuously rather than as a short course. You may start losing the benefit after stopping, with hair tending to return towards its untreated baseline over several months.
Before you commit to long-term treatment, you should make sure your hair loss is actually androgenetic alopecia. If you have hair loss from thyroid problems, iron deficiency, illness or another condition, you may need a different treatment. Getting the right diagnosis first can help you choose the right approach for you.
What Changes Can These Medicines Make to an Enlarged Prostate?
Finasteride and dutasteride lower DHT within the prostate, helping to gradually reduce its size. You may experience improved urinary flow and fewer symptoms, while treatment can also reduce the risk of acute urinary retention and prostate surgery in suitable men.
These medicines work best when your symptoms are linked to an enlarged prostate. Your doctor may consider your prostate size, PSA level and symptoms before recommending treatment. You may also be prescribed an alpha blocker alongside them for faster symptom relief while the prostate gradually responds.
UK Guidance Note
5-alpha-reductase inhibitors may be considered for selected men with urinary symptoms and an enlarged prostate who are at increased risk of progression. Because these medicines act gradually rather than providing immediate symptom relief, treatment is typically reviewed after around three to six months and then periodically.
Are Finasteride and Dutasteride Prostate Cancer Treatments?
Finasteride and dutasteride affect the prostate, but they are not standard treatments for established prostate cancer. In the UK, their licensed use is mainly for benign prostate enlargement, so taking finasteride for hair loss does not mean you are receiving prostate cancer treatment.
You should tell your doctor if you are taking either medicine, particularly when you have PSA testing or other prostate assessments. These medicines can affect PSA levels, so your doctor needs to know you are taking them when interpreting your results.
Why Do These Medicines Matter When You Have a PSA Test?
Finasteride and dutasteride can lower your PSA level, but the amount of reduction depends on the medicine, dose and duration of treatment. Finasteride 5 mg and dutasteride 0.5 mg used for BPH commonly reduce PSA by around 50% after several months, while finasteride 1 mg used for hair loss can also lower PSA. You should therefore always tell your GP or urologist if you take either medicine so your result can be interpreted appropriately.
Your doctor can take the medicine-related reduction into account when assessing your PSA. You should not stop finasteride or dutasteride before a PSA test unless your clinician specifically advises you to do so.
Professor Prasanna Sooriakumaran, Consultant Urological Surgeon at Prostate Clinic London, notes that medicines such as finasteride and dutasteride need to be taken into account when interpreting PSA results, as they can lower PSA levels.
What Sexual Side Effects Should You Know About?
Finasteride and dutasteride can cause sexual side effects because they alter androgen activity. You may experience reduced sexual desire, erection difficulties or changes in ejaculation, although many men take these medicines without significant problems.
If you notice sexual changes, you should discuss them with your doctor rather than stopping treatment yourself. Your doctor can help you consider whether the symptoms may be related to the medicine and what options are available for you.
What Should You Know About Mood and Mental Health?
Finasteride has been associated with depression and suicidal thoughts, while evidence for dutasteride is more limited. Because the medicines work in a similar way, mood changes are an important safety consideration with both treatments.
If you develop low mood, depression or suicidal thoughts while taking either medicine, seek medical advice promptly. If you take finasteride 1 mg for hair loss and develop depression or suicidal thoughts, stop taking it and contact a healthcare professional. If you take finasteride 5 mg or dutasteride, contact your doctor as soon as possible. If you feel at immediate risk of seriously harming yourself, call 999 or seek emergency help.
Do Finasteride and Dutasteride Affect Fertility or Pregnancy Safety?
If you are trying to conceive, you should discuss finasteride or dutasteride with your doctor, as both can affect reproductive parameters in some men. Dutasteride may affect sperm count, semen volume and motility, while finasteride can also affect sexual or reproductive function in some people.
Pregnancy precautions are important because these medicines can affect the development of a male foetus. Women who are pregnant or could become pregnant should not handle broken finasteride tablets or leaking dutasteride capsules. You should also report any breast lump, tenderness, enlargement or nipple discharge to your doctor. If you take dutasteride and your partner is or could be pregnant, discuss pregnancy precautions with your doctor, including how to reduce the possibility of exposure through semen.
What Should You Discuss Before Starting Finasteride or Dutasteride?
Before starting treatment, make sure your doctor knows about your health, medicines and treatment goals. This can help you understand whether the medicine is appropriate for you and what monitoring may be needed.
- Why you need treatment: Confirm whether the medicine is being considered for hair loss, prostate symptoms or another reason.
- Your current medicines: Mention other prescriptions, supplements and any treatment you already use for hair or prostate problems.
- Fertility plans: Tell your doctor if you are trying to conceive or have concerns about reproductive health.
- Mental health history: Tell your doctor if you have previously experienced depression or suicidal thoughts, particularly before starting finasteride.
- Prostate monitoring: Mention any previous PSA tests, prostate investigations or urinary symptoms that may need consideration.
Discussing these points before treatment can help you understand the expected benefits, possible side effects and follow-up needed for your individual situation.
When Should You See a Dermatologist About Finasteride or Hair Loss?
Before you start a DHT-lowering medicine, you should confirm that your hair loss is actually male pattern hair loss. A dermatologist can examine your scalp, review how the hair loss developed and check whether another condition could be causing diffuse shedding or patchy loss.
If you already take finasteride or another 5-alpha-reductase inhibitor for prostate problems, you should discuss this with your dermatologist before using the hair-loss formulation. You can also ask about alternatives such as topical minoxidil and discuss the potential sexual, reproductive and psychiatric effects. If dutasteride is being considered for hair loss, you should ask why an off-label treatment is being proposed and what follow-up you will need.
Myth vs Fact
| Myth | Fact |
| Finasteride and dutasteride are interchangeable. | They inhibit 5-alpha-reductase differently and have different UK licences and pharmacology. |
| Taking 5 mg finasteride should grow more hair than 1 mg. | Increasing the licensed 1 mg hair-loss dose has not been shown to improve efficacy. |
| Dutasteride is licensed for male pattern hair loss in the UK. | Its UK licence is for benign prostate enlargement; hair-loss use is off-label. |
| Taking finasteride means you are being treated for prostate cancer. | Finasteride is used for male pattern hair loss or BPH, not as standard treatment for established prostate cancer. |
| PSA results can be interpreted normally while taking these medicines. | Finasteride and dutasteride can lower PSA, so the clinician interpreting the result needs to know you take them. |
Key Takeaways
- Finasteride and dutasteride reduce DHT but differ in enzyme inhibition, licensed uses and how long they remain in the body.
- Finasteride 1 mg is licensed in the UK for male pattern hair loss, while dutasteride hair-loss treatment is off-label.
- Finasteride 5 mg and dutasteride 0.5 mg are used for selected men with benign prostate enlargement.
- Increasing finasteride above the licensed 1 mg hair-loss dose has not been shown to improve hair-loss efficacy.
- Both medicines can affect PSA interpretation, but the amount of PSA reduction depends on the drug, dose and treatment duration.
- Sexual, reproductive and psychiatric effects should be discussed before treatment, including current psychiatric safety warnings.
Frequently Asked Questions
1. What are finasteride and dutasteride used for?
Both medicines reduce the conversion of testosterone into DHT. Finasteride can be used for male pattern hair loss and benign prostate enlargement, while dutasteride is licensed for benign prostate enlargement in the UK.
2. How does DHT contribute to hair loss?
DHT can cause sensitive scalp hair follicles to gradually become smaller. This produces shorter, finer hairs and can lead to thinning at the temples, front or crown.
3. How does finasteride help male pattern hair loss?
Finasteride lowers DHT and can slow the follicle miniaturisation associated with male pattern hair loss. If you respond to treatment, continued use is generally needed to maintain its effect.
4. What is the difference between finasteride and dutasteride?
Finasteride mainly blocks type II 5-alpha-reductase, while dutasteride blocks both type I and type II. Dutasteride therefore produces a greater reduction in DHT and remains in the body much longer.
5. Is dutasteride licensed for hair loss in the UK?
No. Dutasteride is licensed for benign prostate enlargement in the UK, although it has been studied for male pattern hair loss. Using it for hair loss is considered off-label.
6. How do finasteride and dutasteride help an enlarged prostate?
Both medicines lower DHT within prostate tissue, which can gradually reduce prostate size. This may improve urinary symptoms and reduce the risk of acute urinary retention and prostate surgery in suitable men.
7. Are finasteride and dutasteride treatments for prostate cancer?
No. They are not standard treatments for established prostate cancer and are mainly licensed for benign prostate enlargement. You should tell your doctor if you take either medicine during prostate assessments.
8. Can finasteride or dutasteride affect a PSA test?
Yes. Both medicines can lower PSA. Finasteride 5 mg and dutasteride 0.5 mg commonly reduce PSA substantially during longer-term treatment, while finasteride 1 mg can also lower PSA, so your doctor needs to know which medicine and dose you take.
9. What side effects can finasteride and dutasteride cause?
Possible side effects include reduced sexual desire, erection difficulties and changes in ejaculation. You should also report low mood, depression or suicidal thoughts promptly and seek medical advice.
10. When should you see a dermatologist about hair loss?
You should consider a dermatology assessment before starting DHT-lowering treatment to confirm that you have male pattern hair loss. A dermatologist can also assess other causes and discuss options such as finasteride, topical minoxidil or off-label dutasteride.
Final Thoughts: Finasteride, Dutasteride, Hair Loss and the Prostate
Finasteride and dutasteride both reduce DHT, but their licensed uses, doses, effects and safety considerations differ. If you are considering treatment for hair loss, you should first confirm the cause of your hair loss and discuss the potential benefits, side effects and monitoring with a qualified clinician.
If you would like advice from a dermatologist in London about hair loss or DHT-lowering treatments, you can contact the London Dermatology Centre to discuss your options and arrange a consultation.
References:
- Zhou, Z., Song, S., Gao, Z., Wu, J., Ma, J. and Cui, Y. (2019) ‘The efficacy and safety of dutasteride compared with finasteride in treating men with androgenetic alopecia: a systematic review and meta-analysis’, Clinical Interventions in Aging, 14, pp. 399–406. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC6388756/
- Gupta, A.K., Venkataraman, M., Talukder, M. and Bamimore, M.A. (2022) ‘Finasteride for hair loss: a review’, Journal of Dermatological Treatment, 33(4), pp. 1938–1946. Available at: https://pubmed.ncbi.nlm.nih.gov/34291720/
- Li, Y., Ma, J., Qin, X.-H. and Hu, C.-Y. (2022) ‘The efficacy and safety of dutasteride and finasteride in patients with benign prostatic hyperplasia: a systematic review and meta-analysis’, Translational Andrology and Urology, 11(3), pp. 313–324. Available at: https://pubmed.ncbi.nlm.nih.gov/35402192/
- Escamilla-Cruz, M., Magaña, M., Escandón-Perez, S. and Bello-Chavolla, O.Y. (2023) ‘Use of 5-alpha reductase inhibitors in dermatology: a narrative review’, Dermatology and Therapy, 13(8), pp. 1721–1731. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC10366043/
- Chiappini, S., Corkery, J.M., Guirguis, A., Mosca, A., Murray, M., Arillotta, D., Dattoli, L., Martinotti, G., Bonaccorso, S., Schifano, F. and Schifano, N. (2026) ‘Signal detection of depression and suicidality associated with finasteride and dutasteride: updated pharmacovigilance evidence and recommendations for comprehensive psychiatric assessment’, Brain Sciences, 16(4), 394. Available at: https://www.mdpi.com/2076-3425/16/4/394