Dutasteride side effects

The most common dutasteride side effects are sexual: impotence, lower libido and ejaculation problems, plus breast enlargement or tenderness. On the Avodart label, impotence affected 4.7% of men in the first 6 months against 1.7% on placebo, and the rates dropped after that; in hair loss trials, side effects were similar to finasteride’s.

Dutasteride is FDA-approved only for symptoms of an enlarged prostate (BPH), so prescribing it for hair loss in the US is off-label, and many of the hair products sold online are compounded. Most of the side effect data come from older men in prostate trials, with smaller and shorter hair loss trials in younger men. Here is what each shows.

Side effects on the label, by time on the drug

The label’s main table pools three 2-year BPH trials of more than 4,300 men (mean age 66). It shows drug-related side effects by when they started:

Scroll sideways to see the full table

Two patterns stand out. The sexual effects were concentrated in the first 6 months, and after the first year new cases on dutasteride were close to placebo. Breast changes ran the other way, appearing later and staying above placebo through year 2. Across the three 4-year trials, the label found no rise in sexual effects or breast disorders with longer treatment. Withdrawal for side effects was 4% on dutasteride and 3% on placebo, most often for impotence (1%).

Dutasteride sexual side effects

Two points on the label matter most here. First, it says these sexual effects “may persist after treatment discontinuation” and that dutasteride’s role in that persistence is unknown. Second, they were more common when dutasteride was combined with tamsulosin for BPH: in a 4-year trial, ejaculation disorders affected 11% on the combination against 2% on dutasteride alone.

The hair loss trials, in younger men, found less difference from placebo:

• Gubelin Harcha, 2014: 917 men aged 20 to 50 took dutasteride (0.02, 0.1 or 0.5 mg), finasteride 1 mg or placebo for 24 weeks. The number and severity of adverse events were similar across groups (study).
• Eun, 2010: 153 men aged 18 to 49 took 0.5 mg or placebo for 6 months, with no major difference in adverse events (study).
• Tsunemi, 2016: 120 Japanese men took 0.5 mg for 52 weeks without a placebo group. Drug-related adverse events affected 17%, none led to withdrawal, and the most frequent events were colds, erectile dysfunction and decreased libido, mostly mild (study).

A 2016 meta-analysis of 17 randomized trials of both drugs found the same split. In men with BPH, the drugs raised the risk of sexual dysfunction (relative risk 2.56); in men with hair loss, the increase was not statistically significant (1.21) (Liu et al.). The hair loss trials were smaller and the men younger, so rare effects are harder to detect in them.

Semen and fertility

The label reports a study of healthy men aged 18 to 52 who took dutasteride 0.5 mg or placebo for 52 weeks. Compared with placebo, total sperm count fell 23%, semen volume 26% and sperm motility 18%, while sperm concentration and shape were unchanged. Twenty-four weeks after stopping, total sperm count was still 23% below baseline, and 2 men had drops of more than 90% at 52 weeks with only partial recovery. Average values stayed in the normal range, and the label says the effect on any one man’s fertility is not known. If you are trying to conceive, tell your prescriber before starting.

Breast changes

Breast enlargement and tenderness are listed as common, and male breast cancer appears among reports received after approval. In the three 4-year BPH trials there was 1 case of breast cancer on dutasteride and 1 on placebo, and none in two other 4-year trials. The label says the link between long-term use and male breast tumors is unknown. Tell your prescriber about any breast lump or change.

Mood and other reported effects

Since approval, the label lists reports of depressed mood, testicular pain and swelling, and allergic reactions including rash, itching, hives, swelling, serious skin reactions and angioedema. These reports show a problem has occurred, not how often or that the drug caused it. Contact a clinician the same day about thoughts of self-harm, or call or text 988 in the US.

PSA and prostate cancer

Dutasteride lowers PSA, the prostate cancer screening test, by about 50% within 3 to 6 months. The label says a PSA result in a man on dutasteride for 3 months or more should be doubled before comparing it with normal ranges, and any confirmed rise from the lowest value should be checked. In the 4-year REDUCE trial of 8,231 men aged 50 to 75, high-grade (Gleason 8 to 10) prostate cancer was found in 1.0% on dutasteride against 0.5% on placebo. Finasteride carries the same class warning.

Pregnancy, handling and blood donation

• Pregnancy: dutasteride is contraindicated in women who are pregnant, because it can affect the genital development of a male fetus.
• Handling: women who are or may be pregnant should not handle the capsules, because dutasteride can be absorbed through the skin. A pregnant woman who touches a leaking capsule should wash the area right away with soap and water.
• Swallow whole: the capsule contents can irritate the mouth and throat, so don’t chew or open them.
• Blood donation: wait at least 6 months after your last dose, so donated blood can’t reach a pregnant woman.
• Semen: dutasteride is found in semen, but the label estimates a female partner’s exposure at about 100 times below the levels that harmed male fetuses in animal studies.
• Interactions: the label advises caution with strong, long-term CYP3A4 inhibitors such as ritonavir, because the body clears dutasteride through CYP3A4 and CYP3A5 enzymes.

Dutasteride vs finasteride side effects

The rows on sexual effects come from different trial populations, so they aren’t a direct comparison. Head to head, the 917-man trial found similar adverse events, and a 2019 meta-analysis of 3 trials with 576 men found no significant difference in altered libido, erectile dysfunction or ejaculation disorders between the two drugs (Zhou et al.). The practical differences are how deeply and how long dutasteride acts: it suppresses more DHT, takes months to clear, and needs the blood donation wait. See finasteride side effects and dutasteride vs finasteride for results and cost.

Compounded and topical dutasteride

The trials above tested oral dutasteride capsules. Online, dutasteride for hair loss is often sold as a compounded capsule at low or custom strengths, or as a topical gel or solution, and those products are not FDA-approved and were not part of these trials. At the providers we compare that publish a monthly price, dutasteride hair products cost $39 to $69 a month as of October 2026, from Strut Health’s compounded oral capsule at $39 to its topical at $69. In between, Happy Head lists compounded oral dutasteride at $42 a month ($34 a month on a 12-month supply), and RxSpan MD lists dutasteride capsules at $59 a month with the consult, shipping and support included. Compare them on our hair loss providers list.

The bottom line

Dutasteride’s side effects look much like finasteride’s: uncommon sexual effects that cluster in the first months, breast tenderness, lower PSA and the same pregnancy rules. What sets it apart is how long it lasts, with a 5-week half-life, a 6-month blood donation wait and a sperm count drop still present 24 weeks after stopping. It is off-label for hair loss in the US. See the dutasteride page for the full label summary, compare finasteride 1 mg vs 5 mg, or compare providers on our hair loss providers list and hair loss hub.