Finasteride Side Effects

Finasteride is the most powerful, well-studied, FDA-approved drug for androgenic alopecia (AGA). It stops AGA progression in 80-90% of men and, on average, leads to a 10% increase in hair count over two years. For men wanting a hands-off approach to hair maintenance, finasteride is often an excellent option.

That said, finasteride isn’t for everyone. While its risk of side effects are often overstated online, the drug appears to reduce libido in a certain percentage of men and may induce gynecomastia. The drug can also temporarily lower sperm counts, which might make conception more difficult during its first six months of use. In some men, the use of finasteride appears to increase anxiety and/or depression. 

The true incidence and magnitude of these reports are hard to discern. Depending on the study we cite and the questionnaire design, these effects can range from 1% to 40%. Whether or not one should worry about finasteride side effects may depend on their current hormonal profile and mental health. Keep reading to learn more.

Gynecomastia

Gynecomastia is the growth of male breast tissue. It results from elevated hormones such as prolactin and estrogen. While gynecomastia is estimated to only affect between 0.25-1.00% of people on 5-alpha reductase inhibitors (such as finasteride), those who start the drug with already elevated levels of prolactin and estrogen are likely at a higher risk of its development. 

Drugs like finasteride can raise blood levels of both testosterone and estrogen by 10-30%, depending on the dose. So, for those starting the drug with borderline-high estrogen, the additional lift in estrogen levels may put someone at greater risk of gynecomastia.

Sexual Side Effects

Because it lowers DHT levels (a hormone that helps maintain male sex characteristics), some studies have shown that a percentage of finasteride users report sexual side effects ranging from decreased sex drive to reduced semen volume to erectile dysfunction. Studies vary widely, but incidents could be as low as 1-2% of users.

Female users should be aware that Finasteride can potentially mutate and/or inhibit the development of male fetus genitalia.^[1]dailymed.nlm.nih.gov/dailymed/lookup.cfm As such, pregnant women are neither prescribed finasteride nor advised to even handle the medication. 

Cognitive Side Effects

On hair loss forums, some men taking finasteride have complained of changes to cognition, specifically, a feeling of brain fog since starting therapy. To date, this hasn’t been reported to significant degrees in clinical studies. This may be because even if the effects do exist, it’s likely a subtle, gradual side effect that many may not attribute to the drug. 

Animal models have demonstrated that finasteride can indeed change brain chemistry, especially after transitioning off of the drug. But it’s important to note that animals in those studies take dosages of finasteride thousands of times greater than what is prescribed to humans.

In any case, it’s not unreasonable that those with depression, anxiety, and/or bipolar disorder should proceed with caution and speak with their doctor to closely monitor the effects of finasteride use.

How To Reduce Side Effects Of Finasteride

Regardless of the specific side effect that’s being targeted to reduce, the strategies are all similar: find ways to (1) reduce daily drug exposure, (2) localize the drug’s effects to the scalp, and (3) do lab tests to determine personal risk for certain side effects like gynecomastia. These strategies are outlined in detail below:

Limit Daily Drug Exposure

As a hair loss drug, finasteride is typically prescribed orally at 1mg daily. Having said that, there’s evidence that 0.2mg daily is nearly just as effective at improving hair counts while simultaneously reducing total drug exposure by 80%. For many people, this coincides with a reduction in perceived side effects.

If side effects, or anticipatory anxiety, are a concern, try lowering the dose of the drug from 1mg daily to 0.2mg daily. After all, small clinical studies have demonstrated that doses as low as 0.2mg daily still improve hair counts, and may also confer a slightly smaller magnitude and/or severity of side effects (at least anecdotally).^[2]https://pubmed.ncbi.nlm.nih.gov/10495375/

Unfortunately, finasteride is a hair loss drug that must be continued indefinitely for its effectiveness to remain. When finasteride treatment is stopped, men typically lose what hair regrowth they gained within 3-12 months. For these reasons, it’s not advised to drop below doses equating to 0.2mg daily – as efficacy may rapidly diminish below this threshold.

If finasteride side effects don’t go away with reduced usage, most users report any lingering side effects go away after discontinuing the drug within 2-3 weeks, and for some, up to a few months. If problems persist beyond that, it’s important to contact your prescribing physician.

Localize Finasteride’s Effects to the Scalp

There are two primary ways to localize finasteride’s effects to the scalp. These methods minimize the amount of the drug that circulates throughout the bloodstream, thus minimizing the side effects of finasteride. Both entail switching from an oral to topical formula.

Try a topical formulation

Studies show that – when formulated properly – topical finasteride may reduce the risk of side effects by 30-90%. One 16-month study on 0.005% topical finasteride demonstrated significant hair improvements, no drug-associated side effects, and no impact on blood hormonal levels.^[3]https://dx.doi.org/10.3109%2F09546639709160517 This suggests that any absorption of the drug beyond the scalp was metabolized quickly enough to not impact serum DHT levels.

Other studies have demonstrated that higher doses of topical finasteride also confer benefit, and at smaller reductions of serum DHT (i.e., a proxy for systemic absorption) and perhaps side effects, too.^[4]https://onlinelibrary.wiley.com/doi/full/10.1111/jdv.17738 Having said that, if minimizing side effects are a top priority, we still recommend starting with the minimum viable dose of topical finasteride – 0.005% x 2 mL daily – and working your way up from there.

Try intradermal delivery methods (dutasteride)

Also known as mesotherapy, intradermal delivery methods inject finasteride into the scalp. While there aren’t yet clinical studies of mesotherapy finasteride in reputable journals, there are clinical studies of mesotherapy dutasteride – a drug that is more powerful at reducing DHT levels versus finasteride and that also has a longer half-life (which makes it a better candidate for less-frequent injections into the scalp – since the drug will stay active for longer).

A small number of clinical studies suggest that scalp injections of ~0.01% x 1-2 mL of dutasteride, once every 1-3 months, do not appreciably alter serum hormones, nor do they result in any reported cognitive or sexual side effects. They do, however, lead to statistically significant hair improvements.

Determine Your Risk for Finasteride Side Effects

Determining personal risk ahead of time, and getting a baseline measure of hormonal health, can help people decide if finasteride is right for them. It can also help people keep track of how the drug is influencing their serum hormones.

Testing for Sexual Side Effect Risk

There aren’t yet clinical studies demonstrating the predictability of finasteride side effects related to lowered libido or sexual dysfunction. There are, however, clinical studies suggesting men who are experiencing reduced libidos tend to also have low levels of free testosterone and/or high levels of sex hormone binding globulin.

For these reasons, some clinicians recommend getting these hormones tested prior to starting finasteride. While finasteride isn’t known to have a major influence over these hormones, borderline-abnormal tests may make someone more likely to report these problems, irrespective of whether they’re using hair loss drugs.

Testing for Gynecomastia Risk

For peace of mind, blood tests for prolactin and estrogen can be ordered prior to starting finasteride. Clinical studies do show that finasteride and dutasteride can slightly increase levels of estrogen, and that a rise in estrogen and/or prolactin can be pathogenically linked to the development of gynecomastia, also known as male breast development.^[5]https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/020788s020s021s023lbl.pdf^[6]https://journals.sagepub.com/doi/abs/10.1177/2051415820926301^[7]https://www.ncbi.nlm.nih.gov/books/NBK279105/

If you’re worried about this side effect, test your estrogen and prolactin levels. If they’re within 10-20% of the upper limit for normal, then finasteride or dutasteride use may put you “over the edge” and into that risk category of gynecomastia. Under these circumstances, consider dietary, lifestyle, and/or environmental interventions to lower levels of these into a normal range prior to starting finasteride, and rechecking these hormones regularly or if breast tenderness begins to develop.

Also keep in mind that blood tests for hormones are just proxies for what might be occurring elsewhere in the body. Therefore, it’s entirely possible for serum blood tests to mislead us into thinking we have “normal” levels of hormones, when our tissue hormonal profiles might be out-of-range. The inverse is also true: out-of-range blood hormones don’t always signify out-of-range tissue hormones. So, treat any laboratory test as preliminary, and recognize the science supporting these tests – at least for their predictability of finasteride side effects – is still in its infancy. 

Anyone interested in doing these lab tests can do so with the help of their primary care physician. Or, those based in the U.S. (or any other country that offers direct-to-consumer lab testing) may be able to order tests through the links below.

For more information, see these resources (no affiliate links):

• Direct-To-Consumer Lab Test: Prolactin (U.S. only) ^[8]truehealthlabs.com/product/prolactin
• Direct-To-Consumer Lab Test: Estrogen (U.S. only) ^[9]truehealthlabs.com/product/estradiol-e2

Can We Localize Finasteride Entirely To The Scalp?

Topical finasteride can still go systemic. Having said that, clinical studies also show that daily doses of topical finasteride as low as 0.005% x 2 mL can still produce positive hair parameter changes over 16 months, and without impacting serum DHT levels (a proxy for systemic circulation of the drug).

For those worried about the sexual side effects of finasteride, this formulation of topical finasteride might be most appropriate. However, if you go down this route, you also may want to consider periodically testing serum DHT levels – as members inside our membership community have found that even at these ultra-low dilutions of finasteride, serum DHT tests can still decline by more than 25%. 

Changes to serum DHT levels can help people understand just how much topical finasteride (if any) is going systemic. In general, DHT fluctuations smaller than 20% are considered biologically insignificant.

Directions for how to do this can be found inside our comprehensive finasteride guides, available only to members. 

So, consider these options (and the data) before giving up entirely on finasteride. There are many ways to leverage its power, mitigate its risks, and perhaps take your hair regrowth to a new level.