A Finasteride Overview

Finasteride (Propecia) is a clinically proven medicine used for male pattern hair loss (androgenetic alopecia) and benign prostatic hyperplasia (BPH). 1mg daily doses are used for hair loss while higher 5mg doses are used almost exclusively for BPH. 

Finasteride works in about 90% of users, stopping hair loss and regrowing hair for some men. 63% of users reported they were satisfied with the results after 5 years.

Finasteride works by reducing dihydrotestosterone (DHT) in the body and scalp. DHT is a product of the body naturally breaking down testosterone. When an excess amount of DHT is in the body, it affects the hair follicles negatively, causing them to shrink in size. A shrunken hair follicle results in hair becoming mature faster, thin and weak, all leading to visible hair loss.

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Finasteride Side Effects and Frequency

Almost all medicines have the potential to cause side effects, but not everyone will get them. The important factors to consider are the type of side effects possible and the frequency in which they are likely to occur.

Finasteride 5mg for BPH will cause more frequent side effects than 1mg Finasteride for hair loss. Higher doses increase your risk of side effects for most medicines which is why it is so important to take the lowest effective dose of any treatment. This is why doctors prescribe based on the clinical evidence from many years of studies on drugs like Finasteride.

Sexual side effects are the most common type of side effect of Finasteride. These include:

  • Difficulty gaining or maintaining an erection (ED)
  • Less desire to have sex (Decreased libido)
  • Decreased amounts of semen released during ejaculation

Non-sexual side effects that are uncommon are:

  • Low mood or depression

There are some other listed potential side effects in the patient information leaflet however, the risk of developing one of these rare side effects is not known. Report any side effects that are not expected to your doctor or pharmacist.

The 4 established side effects are well researched with their expected frequencies well established. Erectile dysfunction (ED) was the most common sexual side effect in clinical trials followed by decreases in desire for sex (libido) then decreased semen release. These were all more common with higher doses (5mg) than in 1mg doses for hair loss.

Overall the expected frequency of a given side effect was up to 1 in 100 people taking it, or 1% of users. According to a study looking at 1-5mg doses, in total, the chances of getting a side sexual side effect were about 2.1% to 3.8%.

There is a risk of allergic reactions to the medicines if you are allergic to any listed ingredient in the tablet. These risks are present with most medicines for those with particular allergies so it is recommended to always be aware of ingredients if you have any known allergies.

While there are no known drug interactions with Finasteride and other medicines, the risks may be higher in those who already experience ED, low libido, major depression, or ejaculation problems. If you currently have any other medical conditions, it is important you talk to your doctor about the added risk for you taking Finasteride.

Are Finasteride Side Effects Permenant?

For a vast majority of men, the side effects of Finasteride will disappear after they stop taking the medicine. However, there is much speculation around a debated risk of Finasteride called post-finasteride syndrome (PFS). PFS is the long term persistence of sexual dysfunctions associated with Finasteride use after the medicine has been stopped. It is important to note that PFS has not been officially proven to exist in clinical trials but there is a lot of information, good and bad, on the internet about it. 

This publication looks at both sides of the argument for and against the existence of PFS and uses reliable references to back it up. Ultimately it concludes that more PFS research is required to assist those with the condition and that the knowledge around the condition amongst doctors and other health professionals needs improvement.

PFS does not have a known frequency even though Finasteride has been around for over 30 years. This doesn’t mean it isn’t possible but it would indicate it is exceedingly rare.

How To Reduce Side Effects Of Finasteride

For those on a high dose, lowering the dose can be effective at reducing side effects. Never do this without the advice of the prescribing doctor as you may require the dose prescribed for very good reason.

For men who continue Finasteride even when they experience side effects, in some cases, the side effects may reduce to a level some men find acceptable after 12 months to 5 years. This is only the case for a small percentage of men but was found in clinical studies.

Improving general health and additional causes of ED may assist in reducing sexual dysfunction in men in general. It must be noted however if you experience finasteride side effects, and they bother you, you should speak to a doctor.

Using 0.1% topical finasteride solutions to reduce the side effects compared to oral tablets has been researched. It was found that it can reduce the side effects in some men, although they were still possible. The studies do acknowledge that further research is required and the cost-effectiveness of the topical solution is poor when compared to the tablet.


Finasteride 4 major side effects only have up to a 1% chance each of occurring in each person who uses the treatment. While this risk is very low, side effects are possible and may distress some men. 

Almost always if side effects are experienced, they will go away after stopping treatment. Ultimately the decision to use Finasteride should be made knowing all the potential risks of treatment. If you do not understand any part of this article, we encourage you to talk to your doctor about the potential risks and benefits of finasteride.

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