Dutasteride vs Finasteride: Which DHT Blocker Is Better?

Dutasteride and finasteride both fight hair loss by lowering DHT, but dutasteride blocks more of it — around 90% to finasteride's 70% — because it inhibits both forms of the 5-alpha-reductase enzyme. That can make it more effective, but it's off-label for hair, stays in the body far longer, and may carry a higher side-effect burden. Finasteride is the first-line choice; dutasteride is usually the step-up when finasteride isn't enough.

At a glance

How they differ

Finasteride blocks only the type II form of 5-alpha-reductase, cutting scalp DHT by about 70%. Dutasteride blocks both type I and type II, pushing DHT reduction past 90%. More complete DHT suppression is the entire reason dutasteride can outperform finasteride — and also the reason its side effects can be more pronounced.

Effectiveness

Some head-to-head studies show dutasteride producing greater hair count gains than finasteride, consistent with its stronger DHT suppression. That said, finasteride carries FDA approval for hair loss and a much larger long-term safety record, which is why most clinicians start there.

Side effects and the half-life difference

Both can cause sexual side effects in a minority of men, usually reversible. The key distinction is duration: finasteride clears within days of stopping, while dutasteride lingers for weeks to months.

Which should you use?

For most men the sensible path is to start with finasteride: it's first-line, FDA-approved for hair, and the best-studied option. If finasteride plateaus or doesn't do enough, dutasteride is the logical step-up — but make that move under a doctor's guidance, with its longer half-life and stronger effect in mind.