Medication

Dutasteride

A stronger relative of finasteride that blocks both forms of the enzyme making DHT. In the United States it is used off-label for hair loss, and it stays in the body for months.
Dr. Schwarz, MD · Board-certified dermatologistLast reviewed September 8, 2026
An amber pill bottle labeled Dutasteride tipped over with white tablets spilling out

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Dutasteride is what I reach for when finasteride has been taken properly for a year and the hair keeps going. It blocks both forms of the enzyme, so DHT drops further, and it regrew somewhat more hair head to head. The catch is how long it lasts — weeks to clear, not a day or two, so a side effect will not pass over a weekend. That trade is why I do not use it first.

— Dr. Schwarz, Board Certified Dermatologist

Key Facts

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Also calledAvodart, generic dutasteride
Drug classDual 5-alpha reductase inhibitor, blocking type I and type II
Taken asSoft capsule, usually once a day
Typical courseLong term, for as long as you want the effect
Time to work3 to 6 months, judged at 12 months
Prescription onlyYes, and off-label for hair loss in the United States

What It Is

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Dutasteride is a prescription capsule approved in the United States for an enlarged prostate. Hair loss use is off-label there and in most of Europe. South Korea and Japan approve it for male pattern hair loss at 0.5 mg a day, where most of the hair research comes from. It is not approved for women and is not used in anyone who is pregnant or could become pregnant. Some prescribe it off-label after menopause, on thin evidence.

How It Works

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DHT is made from testosterone by an enzyme called 5-alpha reductase, which comes in two forms. Finasteride blocks type II, the form that dominates in the scalp. Dutasteride blocks both, so DHT falls further — blood levels drop by more than 90%, against roughly two thirds on finasteride. Less DHT means follicles stop shrinking and some shrunken ones regrow thicker.

Finasteride clears in hours; dutasteride's half-life is measured in weeks, and traces stay in the blood for months after the last capsule. That makes the dose forgiving day to day and a side effect slow to settle. It is also why blood donation is deferred for six months after stopping, so a pregnant recipient cannot be exposed.

Here is where Dutasteride acts in the skin, and what the others do instead.

About Dutasteride
Compare
Skin basics
BARRIEREPIDERMISDERMISHAIRSIGNALBLOCKS THE HORMONE SIGNALARRIVES BY BLOODWAKES THE FOLLICLE UP

Pattern hair loss is the follicle shrinking a little more each cycle in response to a hormone signal. Dutasteride blocks that signal, which slows or stops the shrinking. It protects what is there more than it regrows. Blocks both enzymes, so it is stronger. It is off-label for hair.

Dutasteride arrives from the inside, carried to the skin by the blood, rather than crossing the barrier from outside. That is why it works everywhere at once, and why it needs monitoring.

This works on the follicle itself, lengthening the growing phase and widening a shrunken follicle. Hairs already lost can come back, but only while treatment continues — stopping returns things to where they were.

The outer film of dead cells and oil. It holds water in and keeps irritants out, and it is thinner than a sheet of paper. Almost every dry, itchy, stinging skin problem starts here.

The outer layer, and the only one anything in a jar reaches. It renews itself constantly: a cell made at the bottom takes about a month to reach the surface and flake off. Most of what a skincare product does, it does here.

The living layer underneath, holding the blood vessels, the nerves and the collagen. It is where lasting change happens and it is hard to reach: most of what is sold for the skin never gets this far.

What It Treats

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Male Pattern Hair Loss
Male Pattern Hair Loss
Strong evidence
A stronger relative of finasteride that blocks both forms of the enzyme, and head-to-head studies favor it on hair count. In most countries it is not licensed for hair loss and is prescribed off-label, usually when finasteride has not held the line. It stays in the body far longer than finasteride, which matters if you might want to stop.

Not the Best For

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Female Pattern Hair Loss
Female Pattern Hair Loss
Limited evidence
Works the same way as finasteride but blocks more of the conversion, and is sometimes tried when finasteride has not been enough. The evidence in women is smaller still. It stays in the body for months after stopping, so the pregnancy caution matters even more — ask your doctor if you could become pregnant.
Bare scalp
Doesn't work
Where the follicle is gone, no medical treatment brings hair back. Dutasteride protects and thickens what is still there.
Hair loss that is not pattern loss
Doesn't work
It works on DHT-driven pattern loss. Shedding after illness or childbirth, iron or thyroid problems, and scarring hair loss all need their own diagnosis and treatment.

Forms

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Dutasteride is a soft gelatin capsule filled with an oily liquid, swallowed whole. Chewing or opening it releases the contents, which irritate the mouth and throat and can be absorbed through skin — a leaking capsule is a handling problem, not just a mess.

A combination capsule with tamsulosin exists for prostate symptoms. It is not a hair loss product and should not be substituted for the plain capsule.

Compounded topical dutasteride and scalp injections are offered in some clinics, neither standardized and neither well studied.

Strengths

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Only one capsule strength is made, so what changes is how often it is taken.

WeakestStrongest
0.5 mg0.5 mg two or three times a week
The only strength
0.5 mg
The dose studied for hair loss, and the approved dose where it is licensed.
A lower-exposure option
0.5 mg two or three times a week
Used by some prescribers because the drug lingers; less studied for hair.

Dose

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The long half-life shapes everything
Levels build over weeks and settle after a few months, so nothing here is judged quickly.
Starting dose
0.5 mg once a day — the dose used in the hair loss trials and approved for hair where it is licensed.
Alternative schedules
Some prescribers use 0.5 mg two or three times a week, since the drug is still present between doses. Lower exposure, less evidence.
Going up
Nothing above 0.5 mg for this use. Higher doses are not a hair strategy.
Total course
Open-ended. The effect lasts only while you take it, with a long tail after stopping.

How to Take It

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When to take it: Any time of day, with or without food. Swallow the capsule whole — do not chew, open or squeeze it, and do not use one that is leaking. Wash your hands if you touch a damaged capsule.

If you miss a dose: Take it when you remember, or skip it. Never double up. Because the drug lasts weeks, a missed capsule barely changes your levels — a real advantage over finasteride.

What to Expect

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Months 1 to 3Months 3 to 6Months 6 to 12After 12 months
Starting
Months 1 to 3
Nothing visible yet; levels are still building. Some men shed more early as weak hairs are replaced.
Turning
Months 3 to 6
Shedding slows, and hair feels denser before it looks denser. Sexual side effects, if they happen, show up here.
Regrowth
Months 6 to 12
Regrowth appears if it is going to, mostly at the crown and mid-scalp, where dutasteride beat finasteride head to head. The hairline responds too, but stays the hardest area.
Judge it here
After 12 months
Holding what you have is a result. The deeper DHT suppression gives a modest gain over finasteride, not a different category.
If you stop | Slowly backwards
Levels take months to fall, so neither benefit nor side effects disappear quickly.

Side Effects

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Most men notice nothing. The effects that matter are sexual, and they matter a little more here than with finasteride because dutasteride stays in the body for months after the last dose.

Common — expected, and they settle

  • Lower sex drive
  • Trouble getting an erection
  • Less semen The volume, not the sperm count.
  • Breast tenderness Sometimes slight enlargement.

Tell your doctor — worth a call, not an emergency

  • Sexual effects that do not settle They usually improve off the drug, but not always quickly.
  • Low mood Reported, and worth raising rather than sitting with.
  • A breast lump or nipple discharge Needs looking at.
  • A PSA test coming up Dutasteride roughly halves the result. Whoever reads it has to know you take this.

Stop and get care

  • Hives, facial swelling or trouble breathing: A true allergic reaction is rare.

What to Avoid

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  • Opening or chewing the capsules The liquid irritates the mouth and throat and absorbs through skin. Anyone pregnant or who could become pregnant should not handle a damaged capsule — the drug can affect how a male baby's genitals develop.
  • Donating blood within six months The standard deferral is six months, not one, because the drug lingers.
  • Taking it alongside finasteride They do the same job. Doubling up adds risk, not benefit.
  • Judging it before a year Levels take months to settle, so early impressions mean little.
  • Stopping and restarting to test it Weeks off will not clear it, so the test tells you nothing.

Monitoring

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No routine blood tests are needed for a healthy man taking it for hair loss. Monitoring is a review and photographs, as with finasteride.

Two practical points. Dutasteride roughly halves PSA, the prostate blood test, so any doctor ordering one needs to know. Blood donation is deferred for six months after the last capsule, not one month, because it clears so slowly. Nothing accumulates harmfully; the question is whether to continue, not what to test.

If You Stop

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There is no taper. What there is, is a long tail. DHT recovers over weeks to months, not days, and traces stay detectable for months. Hair that was being held is lost over about six to twelve months, ending where it would have been anyway. Side effects are equally slow to settle after stopping, which is a real part of the decision to start.

Cost

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Generic dutasteride is cheap, though it costs more than generic finasteride. Branded Avodart costs far more for the same drug. Hair loss use is off-label in the United States, so insurance rarely covers it and most people pay cash. Compounded topical and injectable versions cost much more on far less evidence.

Ask Your Doctor

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If your partner could be pregnant
Talk about how capsules are stored, and never leave a damaged one lying around.
If you are due a PSA test
The result runs at about half of what it otherwise would.
If you plan to donate blood
You will be deferred for six months after your last capsule.
If you are trying to conceive
Effects on semen are reported and generally reverse, but the slow clearance means planning ahead.
If your mood drops
Raise it early, because this drug takes longer to clear if you stop.
If you notice breast changes
Uncommon, and it should be examined rather than watched.
If you are a woman considering it
It is not approved for women and is not used in anyone who could become pregnant.
If you already take finasteride
The two are not combined; switching is a planned change.

How It Compares

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FinasterideDiagram: how Finasteride works in the skin
Finasteride
Different job
Blocks one form of the enzyme, clears from the body in a day, and has the largest trial base and regulatory approval for hair. The usual first choice, with dutasteride considered after it.
A plain white bottle with a gray applicator tip lying on its side, labeled MinoxidilDiagram of a hair follicle in cross-section, labeled to show that minoxidil keeps the follicle in its growing phase for longer.
Topical minoxidil
Different job
A completely different target, working on the hair cycle. Combined with dutasteride rather than compared against it.
Oral minoxidil at low dose
Different job
Another off-label prescription option, with side effects that are entirely different in kind, including unwanted body hair.
Topical or injected dutasteride
Worse
Aims to keep the drug in the scalp. Not standardized, poorly studied, and absorption still occurs.
Hair transplantDiagram: how Hair Transplant works in the skin
Hair transplant
Different job
The only answer for bare scalp. Medical treatment usually continues afterwards to protect the hair that was not moved.

Myths

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  • "It is approved for hair loss." Not in the United States, where it is approved for an enlarged prostate and used off-label for hair. South Korea and Japan do approve it.
  • "It is just a stronger finasteride, so it is the same drug." It blocks both forms of the enzyme, not one, and stays in the body for weeks rather than hours. The second difference matters more.
  • "It shuts down your testosterone." It lowers DHT, not testosterone, which rises slightly. Not castration, not a steroid.
  • "It stays in your body forever." It clears slowly, with traces for months — not permanently. The six-month donation rule reflects that.
  • "Because it is stronger, the side effects are guaranteed to be worse." Reported side effects are similar in kind and frequency to finasteride, though the hormone suppression is deeper. What differs is how long they take to settle.

Questions Patients Ask

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Is it better than finasteride?

At 0.5 mg it regrew somewhat more hair than finasteride at 1 mg. Better is not first choice, though — off-label in the United States, and far slower to clear.

How long does it stay in my body?

Weeks for most of it, traces for months. That is why donation is deferred six months rather than one.

Can I switch from finasteride?

That is how most people start it — a planned switch, not an addition.

Do I need blood tests?

Not routinely if you are healthy. Anyone ordering a PSA needs to know, because the result runs at about half.

Can my partner handle the capsules?

Intact capsules are fine to handle. Nobody pregnant or who could become pregnant should touch a leaking or damaged one.

What happens if I stop?

DHT recovers over months, not days, and the hair being held is lost over the following six to twelve months.

References

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