Dutasteride is more effective than finasteride at reducing DHT levels and increasing hair counts in clinical trials. Dutasteride blocks approximately 90% of DHT production by inhibiting both Type I and Type II 5-alpha reductase enzymes, while finasteride blocks only Type II, reducing DHT by about 70%. The tradeoff is a modestly higher side effect profile with dutasteride.
Quick Comparison Table
| Factor | Dutasteride (0.5mg) | Finasteride (1mg) |
|---|---|---|
| DHT suppression | ~90% | ~70% |
| Enzyme targets | Type I and Type II 5-AR | Type II 5-AR only |
| FDA approved for hair loss | No (off-label) | Yes |
| FDA approved for BPH | Yes | Yes |
| Half-life | ~5 weeks | 6-8 hours |
| Sexual side effects | 4-6% | 2-4% |
| Monthly cost (generic, US) | $15-50 | $10-30 |
| Time to see results | 3-6 months | 3-6 months |
| Peak results | 12-24 months | 12-24 months |
| Available as generic | Yes | Yes |
How Each Drug Works
Both dutasteride and finasteride belong to the 5-alpha reductase inhibitor class. They prevent testosterone from converting into DHT, the hormone directly responsible for miniaturizing hair follicles in androgenetic alopecia.
Finasteride selectively blocks the Type II isoform of 5-alpha reductase. This isoform is primarily found in the prostate, liver, and hair follicles. At 1mg daily, finasteride reduces serum DHT by approximately 70% and scalp DHT by 40-50%.
Dutasteride blocks both the Type I and Type II isoforms. Type I is found in skin, sebaceous glands, and the liver. By targeting both enzymes, dutasteride achieves serum DHT reduction of approximately 90% and scalp DHT reduction of 50-60%.
The additional 20% systemic DHT suppression and the extra 10% scalp suppression is what gives dutasteride its clinical edge in hair count trials.
Efficacy Comparison
Hair Count Data
In the most significant head-to-head trial (Olsen et al.), dutasteride 0.5mg demonstrated statistically superior hair count increases compared to finasteride 5mg (a dose five times higher than the standard hair loss dose) at both 12 and 24 weeks.
When comparing at standard clinical doses:
| Outcome | Dutasteride 0.5mg | Finasteride 1mg |
|---|---|---|
| Hair count improvement | Greater | Good |
| Hair width improvement | Greater | Good |
| Halt progression | Yes (majority) | 80-90% of users |
| Induce regrowth | Yes (majority) | ~65% of users |
| Patient satisfaction | Higher in trials | Good |
What Finasteride Alone Achieves
Finasteride should not be dismissed. The data is strong:
- 80-90% of men halt further hair loss on finasteride 1mg daily
- Approximately 65% experience some degree of regrowth
- It is the only oral DHT inhibitor FDA-approved for androgenetic alopecia
- Its shorter half-life (6-8 hours) means side effects resolve faster if you stop
For many men, these numbers are enough. Dutasteride becomes the next step only when finasteride falls short.
Side Effect Comparison
Both drugs share similar side effect profiles, with dutasteride showing modestly higher incidence rates:
| Side Effect | Dutasteride | Finasteride |
|---|---|---|
| Decreased libido | 3-5% | 1.5-3% |
| Erectile dysfunction | 3-5% | 1-2% |
| Ejaculation disorders | 1-3% | 0.5-1.5% |
| Breast tenderness | 1-2% | 0.5-1% |
| Breast enlargement | <1% | <0.5% |
Important differences in side effect management:
- Finasteride side effects clear within days to weeks of stopping due to the 6-8 hour half-life
- Dutasteride side effects can persist for weeks to months after stopping because the 5-week half-life means the drug takes much longer to leave your system
- Most side effects for both drugs are reversible upon discontinuation
- Side effect rates from clinical trials may not perfectly match real-world experience, as trial participants are monitored more closely
Which Drug for Which Norwood Stage?
Your Norwood stage plays a role in which medication makes the most sense as a starting point:
| Norwood Stage | Grafts If Surgical | Recommended First-Line | When to Consider Dutasteride |
|---|---|---|---|
| Norwood 2 | 800-1,500 | Finasteride 1mg | If finasteride insufficient at 12 months |
| Norwood 3 | 1,500-2,200 | Finasteride 1mg | If progression continues on finasteride |
| Norwood 3V | 2,000-2,800 | Finasteride 1mg | Vertex thinning not responding to finasteride |
| Norwood 4 | 2,500-3,500 | Finasteride 1mg + consider surgery | As transplant adjunct or finasteride replacement |
| Norwood 5 | 3,000-4,500 | Surgery + medication | Dutasteride as post-transplant maintenance |
| Norwood 6 | 4,000-6,000 | Surgery + medication | Dutasteride as post-transplant maintenance |
| Norwood 7 | 5,500-7,500 | Surgery + medication | Dutasteride as post-transplant maintenance |
Not sure where you fall? Get your Norwood stage assessed at myhairline.ai/analyze.
Pharmacokinetics: Why Half-Life Matters
The half-life difference between these two drugs has practical implications that go beyond simple dosing:
| Pharmacokinetic Factor | Dutasteride | Finasteride |
|---|---|---|
| Half-life | ~5 weeks | 6-8 hours |
| Time to steady state | 3-6 months | 1-2 weeks |
| Time to clear after stopping | 4-6 months | 1-3 days |
| Missed dose impact | Minimal (long buffer) | Moderate (levels drop quickly) |
| Side effect reversibility speed | Slow (weeks to months) | Fast (days to weeks) |
What this means in practice:
If you miss a dose of finasteride, your DHT levels start climbing within hours. Miss a dose of dutasteride, and the drug's reservoir in your body keeps suppressing DHT for weeks. This makes dutasteride more forgiving for inconsistent dosing.
However, this same property works against you if side effects develop. Stopping finasteride clears the drug within days. Stopping dutasteride means waiting weeks to months for the drug to leave your system and for side effects to resolve. This is a significant factor for patients who are risk-averse about side effects.
Combination Therapy Considerations
When adding a second treatment to either drug, the approach differs slightly:
Adding minoxidil to finasteride: This is the most well-studied combination. Finasteride blocks DHT (70% suppression), and minoxidil (40-60% moderate regrowth efficacy) stimulates follicles through vasodilation. The combined effect is greater than either alone.
Adding minoxidil to dutasteride: The same logic applies with even greater DHT suppression (90%). For patients who did not respond sufficiently to finasteride plus minoxidil, switching the DHT blocker to dutasteride while maintaining minoxidil is a common escalation strategy.
Adding PRP to either drug: PRP therapy ($500-$2,000 per session) works through growth factor delivery and is compatible with both finasteride and dutasteride. The choice of oral DHT inhibitor does not affect PRP outcomes.
Cost and Access Differences
Finasteride advantages on access:
- FDA-approved for hair loss, making prescriptions straightforward
- More doctors are comfortable prescribing it
- Slightly cheaper ($10-30/month generic vs $15-50/month for dutasteride)
- Covered by some insurance plans under the hair loss indication
Dutasteride access challenges:
- Off-label for hair loss in the US and most countries (approved in South Korea and Japan)
- Some doctors hesitate to prescribe off-label
- Telehealth hair loss platforms are increasingly offering it
- Insurance rarely covers it for the hair loss indication
For full pricing details, see our full dutasteride vs finasteride breakdown.
Switching from Finasteride to Dutasteride
If your doctor recommends switching, here is what to expect:
- Timing: Most doctors suggest a direct switch without a washout period, since both drugs target the same pathway
- Transition shedding: Some patients report temporary increased shedding during the switch, though this is not universal
- Results timeline: Allow 6-12 months on dutasteride to evaluate its effectiveness compared to your finasteride baseline
- Monitoring: Your doctor may check PSA levels before and during treatment, as both drugs lower PSA readings
Can you take both at the same time?
Taking both simultaneously is not standard practice. Dutasteride already blocks the enzyme that finasteride targets (Type II), plus the additional Type I enzyme. There is no established benefit to combining them, and doing so would increase side effect exposure without clinical justification.
The Hair Transplant Connection
Regardless of which medication you choose, understanding how it fits with potential surgery is important:
- A Norwood 3 patient on finasteride who achieves good stabilization may never need a transplant
- The same patient on dutasteride, if finasteride was not enough, gets a second chance at medication-only management
- If surgery becomes necessary, continuing either medication post-transplant protects native hair
FUE procedures achieve 90-95% graft survival with 7-10 day recovery. But transplanted hair only addresses existing gaps. Your native hair still needs DHT protection, and that is where finasteride or dutasteride plays its long-term role.
Learn more about when to consider surgery in our finasteride vs hair transplant guide.
Making Your Decision
Here is a practical decision tree:
- Starting treatment? Begin with finasteride 1mg daily (FDA-approved, lower side effect risk)
- On finasteride 12+ months with insufficient results? Talk to your doctor about switching to dutasteride 0.5mg
- Concerned about side effects? Stick with finasteride. Its shorter half-life provides faster reversibility
- Norwood 4+ and considering surgery? Discuss dutasteride as a transplant adjunct with your surgeon
- Not sure about your stage? Start with a free assessment at myhairline.ai/analyze
The best treatment is the one you will take consistently. Both drugs only work while you are taking them, and both require a long-term commitment. Understanding the differences helps you make an informed choice with your doctor.
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Dutasteride is not FDA-approved for hair loss treatment. Always consult a qualified healthcare provider before starting or switching medications.