The Bottom Line

Dutasteride is a prescription medication that blocks DHT — the hormone responsible for shrinking hair follicles in male pattern baldness. It suppresses DHT more completely than finasteride (90–95% vs. 70%), and clinical trials show it produces greater hair count improvement. However, it has more sexual side effects and is not FDA-approved for hair loss in the US. It's typically used when finasteride hasn't worked well enough.

What Is Dutasteride?

Dutasteride (brand name Avodart) is an oral medication FDA-approved for benign prostatic hyperplasia (enlarged prostate) but used off-label for androgenetic alopecia — male pattern hair loss. It works by blocking an enzyme called 5-alpha reductase, which converts testosterone into dihydrotestosterone (DHT).

DHT is the hormone that gradually miniaturizes hair follicles in people with a genetic predisposition to baldness. By blocking DHT production, dutasteride helps preserve existing follicles and can stimulate some regrowth.

How Is Dutasteride Different From Finasteride?

There are two types of 5-alpha reductase: type I and type II. Finasteride only blocks type II. Dutasteride blocks both types, giving it more complete DHT suppression:

  • Dutasteride: reduces DHT by 90–95% in the blood; 85–95% in scalp tissue
  • Finasteride: reduces DHT by 65–75% in the blood; 40–60% in scalp tissue

This extra blockade translates into real clinical differences. In a head-to-head 24-week trial, dutasteride 0.5 mg daily produced 41% hair count improvement versus finasteride's 19%. Longer studies show 65–75% of dutasteride users achieve meaningful hair count improvement compared to 40–50% with finasteride.

What Kind of Results Can You Expect?

  • 3–6 months: Hair loss stabilizes
  • 12–18 months: Visible regrowth begins
  • 24–36 months: Maximum benefit reached
  • After stopping: Hair loss resumes within 3–6 months — long-term use is needed to maintain results

Dosing

The standard dose for both prostate enlargement and off-label hair loss is 0.5 mg once daily. Because dutasteride has a very long half-life (4–6 weeks), missing an occasional dose has less impact than with finasteride. Some research suggests lower doses (0.1–0.25 mg) may also suppress DHT effectively with potentially fewer side effects, though this is still being studied.

Side Effects

Because dutasteride suppresses DHT more completely, it does come with a somewhat higher rate of sexual side effects than finasteride:

  • Erectile dysfunction: 5–7% (vs. 3–4% with finasteride)
  • Ejaculation issues: 7–9% (vs. 4–5% with finasteride)
  • Reduced libido: 4–6% (vs. 2–3% with finasteride)
  • Breast tenderness or enlargement (gynecomastia): 0.5–1%

These side effects develop mostly in the first 3 months, and 60–70% of men who experience them find they improve or resolve — even while continuing the medication.

Teratogenicity: Like finasteride, dutasteride can cause abnormal development of male fetuses. Women who are pregnant or may become pregnant should not handle broken tablets, and men taking it should use condoms if their partner could become pregnant.

Who Is Dutasteride Best For?

Finasteride remains the first-line medication because of its well-established safety record, FDA approval for alopecia, and lower cost (roughly $0.50–$2/month vs. $3–$5/month for dutasteride). Dutasteride is typically considered for:

  • Men who tried finasteride for at least 12 months without adequate response
  • Men who had partial results on finasteride and want greater DHT suppression
  • Men living in countries where dutasteride is formally approved for alopecia (such as South Korea and Japan)

When to See a Dermatologist

  • You've been on finasteride for 12+ months with minimal results
  • You want to understand whether dutasteride is appropriate for your hair loss pattern and health history
  • You're experiencing sexual side effects on finasteride and want to discuss whether switching makes sense
  • You want a baseline assessment of your hair loss stage before starting treatment

Frequently Asked Questions

Is dutasteride better than finasteride for hair loss?

Clinical trials suggest dutasteride produces superior hair count improvement (60–75% vs. 40–50% with finasteride) due to more complete DHT suppression. However, finasteride remains the first choice because it has more long-term safety data, FDA approval for hair loss, and lower cost.

How long does dutasteride take to show results?

Hair loss stabilizes within 3–6 months, and visible regrowth becomes apparent around 12–18 months. Full benefit takes 24–36 months, which is slightly faster than finasteride's plateau.

Are sexual side effects more common with dutasteride than finasteride?

Yes, modestly so. Dutasteride shows slightly higher rates of erectile dysfunction (5–7% vs. 3–4%) and ejaculation issues (7–9% vs. 4–5%). Most of these effects resolve over time, even without stopping the medication.

Can I switch from finasteride to dutasteride?

Yes. Men who haven't responded adequately to finasteride after 12 months can switch to dutasteride. The increased DHT suppression may benefit partial responders. Allow at least 3 months on dutasteride before evaluating the switch's effect.

  1. Roehrborn CG, et al. Efficacy and safety of dutasteride in men with benign prostatic hyperplasia. Urology. 2002;60(3):434-441.
  2. Andriole GL, et al. The REDUCE trial: Design and rationale. Rev Urol. 2006;8(Suppl 1):S3-S11.
  3. Gormley GJ, et al. The effect of finasteride in men with benign prostatic hyperplasia. N Engl J Med. 1992;327(17):1185-1191.
  4. Blumeyer A, et al. Evidence-based guideline for the treatment of androgenetic alopecia. J Eur Acad Dermatol Venereol. 2011;25(Suppl 12):1-47.
  5. Vereecke D, et al. Dual inhibition of 5alpha-reductase and aromatase. Steroids. 2016;105:59-74.

Trusted Resources

Always consult a board-certified dermatologist before starting or changing any treatment for hair loss.