“He told me to stop taking it immediately,” Will, now 32, said.
Finasteride, sometimes sold as Propecia, is a widely used prescription medicine for male-pattern baldness.
For many, the medication comes with no issues and can provide newfound confidence, but it does carry side effects. Will had known there was a small possibility of reduced libido and erectile dysfunction (between 1 and 2%), but he didn’t know that the drug might be linked to his fertility struggles.
Finasteride is prescribed at higher doses to treat enlarged prostates and has been known to mildly affect sperm counts. But Dr James Kashanian, a urologist and the director of male sexual health at Weill Cornell Medicine, said the drug has also “significantly affected” some patients’ sperm quality, even at 1mg, the dose typically prescribed for hair loss.
Unlike with other side effects of the drug, it’s not clear how common reduced sperm counts are, and much of the data is anecdotal. While some doctors say that it can be a significant problem, especially among men already struggling with fertility issues, others say it plays a relatively small role.
Still, many young men are not aware of any potential risks, said Dr Mary Samplaski, a urologist and the former director of male infertility at the Keck School of Medicine at the University of Southern California.
Will had been prescribed finasteride for hair loss through the telehealth company Hims & Hers. A senior vice president at the company said it provides information about finasteride when patients are prescribed it and includes a warning on its website about infertility and poor sperm quality.
In most cases, fertility issues seem to reverse within a few months of going off the medication and there is no evidence it causes birth defects. In Will’s case, he stopped taking it the day his urologist told him to. When he tested again 10 weeks later, his sperm count had jumped to 250 million per millilitre, a 125-fold increase.
A “male contraceptive”?
In 1999, the first peer-reviewed study to look at finasteride and sperm quantity found no effects. (The researchers received financial support from the pharmaceutical company Merck & Co.) But a small 2013 study, led by Samplaski, focused specifically on 27 men dealing with infertility issues while taking finasteride. Researchers asked them to go off the drug for three months, the amount of time it typically takes for a new population of sperm to form. When the men were retested after going off finasteride, they registered an 11-fold increase in sperm counts on average.
Researchers suspect that the reason for the decline in sperm count is that the medication can shift the balance of hormones in the body, said Dr Scott Lundy, the programme director of urology at the Cleveland Clinic. It does this by suppressing the conversion of testosterone to dihydrotestosterone, or DHT, which has been found to lead to baldness.
For some people, disrupting hormonal ratios can create fertility issues. “A lot of people don’t know that testosterone is a male contraceptive,” said Dr Kirk Lo, a urologist at Mount Sinai Hospital in Toronto who worked on the study with Samplaski.
However, there are very few high-quality studies looking at finasteride and sperm counts, and not every doctor considers it a particularly common factor in male fertility issues. Dr Kian Asanad, the director of the USC Fertility and Men’s Sexual Health Centre, said he will mention finasteride’s potential effects on fertility to patients when relevant, but that he couldn’t recall a case when taking a patient off finasteride solved their fertility issues independently.
“I don’t think it’s as common as we really think, but I think it’s something that we definitely keep in mind as fertility specialists,” Asanad said.
In the US, Kashanian said he has had more conversations about finasteride in recent years as more men have come in seeking treatment for infertility.
Dr Marc Goldstein, the surgeon-in-chief of male reproductive medicine at Weill Cornell Medicine, agreed and said after he lays out the risks of taking finasteride while trying to conceive, some patients will choose to stay on the medication. “Vanity reigns supreme,” he said.
But others, like Will, are happy to go off. After his sperm count rebounded, last year he and his wife had a healthy baby boy. He has no plans to go back on finasteride any time soon.
“I’d have gladly lost every hair on my head to have the kid we have now,” he said.
This article originally appeared in The New York Times.
Written by: T.M. Brown
©2025 THE NEW YORK TIMES
