Finasteride and Dutasteride are the two FDA-approved oral 5-alpha reductase inhibitors used to treat androgenetic alopecia. Dutasteride is clinically more potent, but Finasteride remains the standard first-line treatment due to its established safety profile and lower side effect rate. This comparison covers every factor you need to make an informed decision.
How They Work
Both drugs block the enzyme 5-alpha reductase, which converts testosterone into dihydrotestosterone (DHT). DHT is the primary hormone responsible for follicle miniaturization in androgenetic alopecia. The critical difference is which enzyme types each drug targets.
Finasteride (Propecia)
- Blocks Type II 5-alpha reductase only
- Reduces scalp DHT by approximately 60-70%
- Dosage: 1 mg daily (oral)
- FDA-approved for male pattern hair loss
Dutasteride (Avodart)
- Blocks both Type I and Type II 5-alpha reductase
- Reduces scalp DHT by approximately 90-95%
- Dosage: 0.5 mg daily (oral)
- FDA-approved for benign prostatic hyperplasia (BPH); used off-label for hair loss
- Approved for hair loss in South Korea and Japan
Head-to-Head Efficacy Comparison
| Metric | Finasteride (1 mg) | Dutasteride (0.5 mg) |
|---|---|---|
| DHT reduction (scalp) | 60-70% | 90-95% |
| DHT reduction (serum) | ~70% | ~90% |
| Halt further loss | 80-90% | 90-95% |
| Produce regrowth | ~65% | ~75% |
| Hair count increase (6 months) | Baseline | ~20% higher than Finasteride |
| Onset of effect | 3-6 months | 3-6 months |
| Peak results | 12-24 months | 12-24 months |
| Half-life | 6-8 hours | 4-5 weeks |
The longer half-life of Dutasteride means it stays in your system for weeks after you stop taking it. This is relevant both for side effect duration and for treatment planning.
Side Effects Comparison
Both medications share a similar side effect profile, but Dutasteride has a higher reported incidence.
| Side Effect | Finasteride | Dutasteride |
|---|---|---|
| Decreased libido | 2-4% | 3-6% |
| Erectile dysfunction | 1-3% | 2-5% |
| Decreased ejaculate volume | 1-2% | 2-3% |
| Breast tenderness | <1% | 1-2% |
| Reversible on discontinuation | Yes (within weeks) | Yes (may take months due to half-life) |
A key distinction: because Dutasteride has a half-life of 4-5 weeks (compared to 6-8 hours for Finasteride), side effects may persist longer after stopping the drug. Finasteride side effects typically resolve within 1-2 weeks of discontinuation, while Dutasteride may take several months.
Efficacy by Norwood Stage
Your current stage of hair loss influences which drug is likely to be more effective.
Norwood 2 (slight temple recession, 800-1,500 grafts if transplant needed)
Finasteride stabilizes loss in approximately 90% of Norwood 2 patients. The additional potency of Dutasteride is rarely needed at this stage. Recommendation: Start with Finasteride.
Norwood 3 (deep temple recession, 1,500-2,200 grafts)
Finasteride remains effective for most Norwood 3 patients, with an 80% stabilization rate. Dutasteride may be considered if Finasteride does not produce sufficient results after 12 months. Recommendation: Start with Finasteride; switch to Dutasteride if needed.
Norwood 4 (enlarged vertex area, 2,500-3,500 grafts)
At this stage, the more complete DHT suppression from Dutasteride may provide a meaningful advantage, particularly for vertex thinning where Type I and Type II receptors are both active. Recommendation: Finasteride first, but Dutasteride is a strong second-line option.
Norwood 5-7 (extensive loss, 3,000-7,500 grafts)
With advanced hair loss, medication alone is unlikely to restore full density. Both Finasteride and Dutasteride serve primarily as stabilizers to protect remaining hair and support transplant results. Recommendation: Dutasteride may offer marginal benefit over Finasteride, but surgical restoration is typically the primary path.
Cost Comparison
| Factor | Finasteride | Dutasteride |
|---|---|---|
| Generic available | Yes | Yes |
| Monthly cost (generic) | $5-$15 | $10-$30 |
| Insurance coverage | Often covered | Less commonly covered (off-label) |
| Requires prescription | Yes | Yes |
Finasteride is more affordable and more widely covered by insurance because it has an FDA-approved indication for hair loss. Dutasteride is prescribed off-label in most countries (except South Korea and Japan), which can affect insurance coverage.
Switching from Finasteride to Dutasteride
If you have been on Finasteride for 12+ months without adequate stabilization, switching to Dutasteride is a common next step. Here is what to expect during a switch:
The Transition Protocol
- Stop Finasteride: Your doctor may instruct you to stop Finasteride and begin Dutasteride the same day, or overlap them briefly
- Expect a lag: Dutasteride takes 3-6 months to reach steady-state blood levels due to its long half-life
- Track density: Continue monthly photo tracking to compare Dutasteride's effect to your Finasteride baseline
- Reassess at 12 months: Full Dutasteride response should be visible by this point
What the Data Shows
Patients who switch from Finasteride to Dutasteride typically see additional density improvement within 6-12 months of the switch. The magnitude of improvement varies, but clinical data suggests approximately 10-20% more hair retention compared to continuing on Finasteride alone.
Combination Therapy Options
Both Finasteride and Dutasteride can be combined with other treatments for improved results. Common combinations include:
| Treatment | Mechanism | Added Benefit |
|---|---|---|
| Minoxidil 5% (topical) | Increases blood flow to follicles | 40-60% moderate regrowth rate |
| PRP therapy | Growth factor stimulation | 30-40% density increase in clinical studies |
| Microneedling | Triggers wound healing response | Enhanced topical absorption |
| Low-level laser therapy | Stimulates cellular energy | Modest density improvement |
The most common combination is a DHT blocker (Finasteride or Dutasteride) plus Minoxidil. This dual approach targets hair loss through two different mechanisms.
How to Decide
Use this decision framework:
Choose Finasteride if:
- You are starting DHT blocker therapy for the first time
- You are at Norwood 2-3
- You prefer a drug with a shorter half-life and faster side effect resolution
- Cost or insurance coverage is a concern
Choose Dutasteride if:
- Finasteride has not produced adequate stabilization after 12 months
- You are at Norwood 4+ and want maximum DHT suppression
- Your doctor recommends it based on your specific pattern
- You are planning a hair transplant and want maximum stabilization beforehand
Know Your Stage First
Before choosing between Finasteride and Dutasteride, you need to know your current Norwood stage. Upload a photo at myhairline.ai/analyze for a free AI assessment that includes your Norwood classification, density estimate, and graft projection.
Read our Norwood scale complete guide for detailed stage descriptions, and see the hair loss treatment hierarchy to understand where DHT blockers fit in the overall treatment landscape.
Medical disclaimer: This article is for informational purposes only. Both Finasteride and Dutasteride are prescription medications with potential side effects. Never start, switch, or discontinue medication without guidance from a licensed healthcare provider. Finasteride side effects are reported in 2-4% of users; Dutasteride side effects are reported at a somewhat higher rate.