Oral finasteride lowers DHT levels throughout the body, which helps reduce hair loss and shrink the prostate. However, it can sometimes bring unwanted side effects, such as sexual problems.
Topical finasteride mainly works on the scalp. Because of this local action, it often has fewer effects on the rest of the body. Still, using the right dose is important to avoid problems.
In this article, we’ll break down how oral and topical finasteride work, compare their results, explain dosing, and go over possible side effects.
| 🔑 Key Takeaways ➤ Oral finasteride lowers a strong hormone (DHT) in your whole body to slow hair loss and shrink the prostate. ➤ Topical finasteride works mainly on your scalp and often has fewer effects on the rest of your body. ➤ You must take oral finasteride every day and wait several months to see hair growth or prostate relief. ➤ Topical finasteride needs precise dosing because too much can still get into your blood and cause side effects. ➤ Low-strength topical finasteride can boost hair growth while lowering the chance of sexual side effects. ➤ Both pill and scalp treatments only keep working if you keep using them regularly. |
Mechanism of Action
Oral finasteride lowers DHT levels in the body to reduce hair loss and prostate size, while topical finasteride mainly works on the scalp with fewer effects on the rest of the body.
Oral Finasteride
According to a study, oral finasteride works by being a competitive inhibitor of the type II and III forms of the enzyme 5-alpha reductase. This enzyme is normally responsible for converting testosterone into dihydrotestosterone (DHT), a powerful hormone that plays a big role in hair loss and prostate growth. By blocking this enzyme, finasteride helps reduce DHT levels, which leads to less hair loss and smaller prostate size.
Oral finasteride cuts down prostatic DHT by up to 90% and serum DHT by about 70%. However, raising the dose doesn’t always lower DHT levels further. Interestingly, DHT levels bounce back to normal within 14 days if you stop taking the drug.
So, the benefits last only as long as you continue treatment.
Topical Finasteride
Topical finasteride also targets 5-alpha reductase in the scalp but with a key difference — it mostly works at the local skin level rather than throughout the whole body. This local action reduces scalp DHT while having a much smaller effect on serum DHT levels. That means topical finasteride may help decrease hair loss in a focused way without significantly lowering the DHT in your bloodstream.
This local targeting is why some researchers are interested in it as a possibly safer option for people worried about systemic side effects.
Dosage and Administration
Oral finasteride is taken daily for hair loss or prostate issues, while topical finasteride is applied to the scalp in carefully measured doses to help hair growth with fewer effects on the whole body.
| Form | Dosage |
| Oral for BPH | 5 mg once daily |
| Oral for hair loss | 1 mg once daily |
| Topical (0.25%) | 1 mL once daily → ~20% serum DHT drop1 mL twice daily → ~70% serum DHT drop |
| Topical (1%) | Twice daily → ~equal to 1 mg oral finasteride |
| Topical (0.005%–0.02%) | 1–2 mL daily → minimal systemic absorption |
Oral Finasteride
Oral finasteride is typically taken once a day, and the dose depends on the condition being treated. For benign prostatic hyperplasia (BPH), the usual dose is 5 mg per day.
Meanwhile, for male pattern hair loss, men usually take 1 mg per day. It’s important to know that you can take it with or without food, and you should swallow the tablet whole with water — no crushing or breaking.
What if you missed a dose? If it’s been less than 6 hours, take it when you remember. But if it’s been longer, just skip it and stick to your usual schedule — never double up. Oral finasteride needs time to work.
For hair loss, you may need to wait at least 3 months to see results, and for BPH, it can take up to 6 months. Stopping the medicine usually leads to the return of symptoms or hair loss within months.
So, consistency matters a lot here.
Topical Finasteride
Topical finasteride has been tested in a 24-week study using a 0.25% solution at 2.275 mg/mL, showing hair regrowth results similar to oral finasteride. However, the right dose and frequency really matter to avoid the drug leaking into the bloodstream, which can cause side effects.
One study using 1% topical finasteride twice daily found that it worked just like oral finasteride (1 mg/day) but also reduced serum DHT by about 71%. In contrast, applying 1 mL of 0.25% topical finasteride once a day lowered serum DHT by only ~20%, but applying it twice daily lowered serum DHT by ~70%.
Another study with a very low 0.005% solution applied twice daily caused no meaningful change in serum DHT — a sign of little to no systemic absorption.
This means that using 1–2 mL of a low-concentration topical solution (0.005–0.02%) per day might provide good scalp benefits while minimizing body-wide effects.
Efficacy
Oral finasteride is very effective at improving hair growth and preventing loss, while topical finasteride also boosts hair counts with fewer body-wide side effects.
Oral Finasteride
According to a study, oral finasteride at a dose of 1 mg per day showed powerful effects in treating androgenetic alopecia (AGA). In their study of 65 men over 12 months, the oral finasteride group saw a clinical improvement in 80% of participants (32 out of 40), based on increased hair density. That’s impressive when you compare it to the topical minoxidil group, which only showed a 52% improvement (13 out of 25). Also, about 7 out of 40 men on oral finasteride experienced mild side effects, like reduced libido or body hair changes. Though these side effects stopped once treatment ended, systemic treatments can come with a price.
Still, the study concluded that oral finasteride was more effective than topical minoxidil, with a statistically significant difference.
Jumping over to Japan, one study looked at oral finasteride in a slightly different way. The researchers divided 37 patients into two groups:
- Those with lots of body hair
- Those without
After at least six months of taking 1 mg/day oral finasteride, 88.9% of the body-hairy group (16 out of 18) saw excellent or good improvement on their scalp. Meanwhile, only 31.6% (6 out of 19) of the less hairy group reported the same results. This suggests that oral finasteride may work even better in people with higher androgen levels.
But interestingly, none of the patients reported changes in their body hair, showing that oral finasteride mainly works on the scalp.
According to a study, a large trial with 1,879 men showed that oral finasteride improved hair growth in 48% of men after one year and in 66% after two years. Even more impressive, it prevented further hair loss in 83% of patients over two years, compared to only 28% in the placebo group.
So, if you’re wondering about long-term results, oral finasteride holds up very well.
Topical Finasteride
According to a study, topical finasteride also packs a punch when it comes to treating AGA. In their large, 24-week European trial with 458 men, topical finasteride significantly boosted hair counts compared to placebo. Specifically, the adjusted mean hair increase was 20.2 hairs in the treatment group versus 6.7 hairs in the placebo group. Even more interesting, the effect of topical finasteride was “numerically similar” to oral finasteride, meaning it came close to matching the pill’s results.
At the 12-week mark, the study already saw significant improvements in hair count with topical finasteride, which continued through week 24. Investigators also noted visible improvements in hair growth and loss patterns. And when it came to safety, topical finasteride really shone. It had more than 100 times lower plasma finasteride levels compared to oral treatment.
Plus, its reduction in serum DHT was less dramatic—34.5% compared to 55.6% with oral finasteride. This lower systemic impact suggests a smaller risk of side effects like sexual dysfunction.
Side Effects
Oral finasteride can cause sexual and other body-wide side effects, while topical finasteride mainly causes mild skin reactions and is usually better tolerated.
Oral Finasteride
Oral finasteride is linked to sexual side effects, although these are rare. Specifically, it can cause:
- Erectile dysfunction
- Decreased libido (less interest in sex)
- Reduced ejaculation or low semen volume
- Insomnia
Oral finasteride can also bring on:
- Decreased interest in sexual intercourse
- Inability to have or keep an erection
- Loss in sexual ability, desire, drive, or performance
- Decreased amount of semen
- Testicular pain
- Back pain
- Diarrhea
- Dizziness
- Headache
- Stomach pain
- Sleepiness or unusual drowsiness
- Runny or stuffy nose
- Sneezing
More severe reactions include:
- Breast enlargement and tenderness
- Clear or bloody nipple discharge
- Breast lumps or dimpling
- Inverted nipple
- Breast redness or swelling
- Skin sores on the breast that do not heal
- Redness or skin rash
- Rapid weight gain or loss
- Swelling of face or limbs
- Tingling in hands or feet
- Chills, cold sweats, confusion
- Lightheadedness when standing
Topical Finasteride
Topical finasteride, on the other hand, is often chosen because people hope to avoid the sexual side effects of the oral form. But what does the research say?
According to the FDA, there have been 32 cases of adverse events reported between 2019 and 2024 for compounded topical finasteride. Reported systemic side effects, similar to oral finasteride, include:
- Erectile dysfunction
- Anxiety
- Suicidal ideation
- Brain fog
- Depression
- Fatigue
- Insomnia
- Decreased libido
- Testicular pain
Additionally, the FDA noted specific local reactions with topical finasteride, which include:
- Skin irritation
- Redness (erythema)
- Dryness or scaling
- Stinging
- Burning sensation
Many patients, according to FDA reports, said they were not informed about these potential side effects and some continued to experience them even after stopping treatment.
According to a study, topical 0.25% finasteride, used alone or with 5% minoxidil, was well-tolerated over six months, with no sexual side effects reported. Minor local side effects included:
- Scaling
- Increased hair shedding at the start of treatment
- Dryness
- Itching
- Headache
Seven patients still reported itching and dryness at six months, but none dropped out because of these issues.
Final Words
Ultimately, both options only work when you stick with them. So, consider your comfort with daily pills or scalp applications. Think about potential side effects and how quickly you want to see changes. Then ask yourself: “Which approach fits your lifestyle and goals?”
Frequently Asked Questions
What’s the difference between oral and topical Finasteride?
Oral Finasteride is a daily pill, while topical Finasteride is a liquid you put on your scalp.
Which works better — oral or topical Finasteride?
Both work well, but oral Finasteride has been studied more. Topical Finasteride may have fewer body-wide side effects.
Can I use oral and topical Finasteride together?
No, using both at the same time can increase side effects. Always ask your doctor before combining treatments.
Sources
- Zito, P. M., Bistas, K. G., Patel, P., & Syed, K. (2024). Finasteride. In StatPearls [Internet]. StatPearls Publishing. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK513329/
- Arca, E., Açikgöz, G., Taştan, H. B., Köse, O., & Kurumlu, Z. (2004). An open, randomized, comparative study of oral finasteride and 5% topical minoxidil in male androgenetic alopecia. Dermatology, 209(2), 117–125. https://doi.org/10.1159/000079595
- Inadomi, T. (2014). Efficacy of finasteride for treating patients with androgenetic alopecia who are pileous in other areas: A pilot study in Japan. Indian Journal of Dermatology, 59(2), 163–165. https://doi.org/10.4103/0019-5154.127677
- Kaufman, K. D., Olsen, E. A., Whiting, D., Savin, R., DeVillez, R., Bergfeld, W., Price, V. H., Van Neste, D., Roberts, J. L., Hordinsky, M., Shapiro, J., Binkowitz, B., & Gormley, G. J. (1998). Finasteride in the treatment of men with androgenetic alopecia. Journal of the American Academy of Dermatology, 39(4 Pt 1), 578–589. https://doi.org/10.1016/s0190-9622(98)70007-6
- Piraccini, B. M., Blume‐Peytavi, U., Scarci, F., Jansat, J. M., Falqués, M., Otero, R., Tamarit, M. L., Galván, J., Tebbs, V., Massana, E., & the Topical Finasteride Study Group. (2021). Efficacy and safety of topical finasteride spray solution for male androgenetic alopecia: A phase III, randomized, controlled clinical trial. Journal of the European Academy of Dermatology and Venereology, 36(2), 286–294. https://doi.org/10.1111/jdv.17738
- U.S. Food and Drug Administration. (2025). FDA alerts health care providers, compounders and consumers of potential risks associated with compounded topical finasteride products. Food and Drug Administration. Retrieved from https://www.fda.gov/drugs/human-drug-compounding/fda-alerts-health-care-providers-compounders-and-consumers-potential-risks-associated-compounded