Methotrexate can contribute to erectile dysfunction, though it is considered a rare side effect. The FDA prescribing information for methotrexate lists “loss of libido/impotence” among adverse reactions that have been reported in patients taking the drug. That said, separating the medication’s direct effects from the impact of the underlying disease is not straightforward, and both likely play a role for many men.
What the Prescribing Label Says
The FDA-approved label for methotrexate explicitly includes loss of libido and impotence in its list of adverse reactions. It also warns that methotrexate can cause low sperm counts and impaired fertility in men, both during treatment and for some time after stopping. These effects are categorized as rare, meaning they don’t show up in most patients, but they are formally recognized rather than purely anecdotal.
How Methotrexate Could Affect Erections
There are several biological pathways through which methotrexate may interfere with sexual function. The most studied involves the testicles. Methotrexate can reduce testosterone production and raise levels of follicle-stimulating hormone (FSH), a pattern that signals the testes aren’t working at full capacity. Lower testosterone directly reduces sex drive and can make achieving and maintaining erections more difficult.
In some men, methotrexate shifts the balance between estrogen and testosterone, nudging the ratio toward estrogen. This hormonal shift can dampen sexual desire and has also been linked to breast tissue growth (gynecomastia) in male patients on the drug. Methotrexate may also influence prolactin levels by blocking certain immune signaling molecules that regulate hormone release from the pituitary gland. Elevated prolactin is a well-known cause of erectile problems.
A separate line of evidence points to nitric oxide, the molecule your blood vessels rely on to relax and allow increased blood flow during an erection. Lab studies have shown that methotrexate inhibits nitric oxide production in a dose-dependent way, meaning higher concentrations suppress it more. While this research was conducted in lung cells rather than penile tissue, nitric oxide pathways are shared across the vascular system, and any drug that broadly suppresses nitric oxide production could theoretically impair the blood-flow mechanics of an erection.
Methotrexate also disrupts trace mineral levels, particularly zinc. Animal research has demonstrated that methotrexate depletes zinc in the testes and causes visible damage to the tissue that produces sperm and hormones. Zinc supplementation in those studies protected testicular structure, suggesting that mineral depletion is part of how the drug causes reproductive harm. Zinc is essential for testosterone synthesis, so a deficiency could compound any direct hormonal effects.
The Disease Itself Raises ED Risk
Most people taking methotrexate have rheumatoid arthritis, psoriatic arthritis, or another inflammatory condition. These diseases independently increase the risk of erectile dysfunction, making it harder to pin the blame entirely on the medication. In a large population-based study using national health survey data, 11.11% of men with rheumatoid arthritis reported ED, compared to just 3.82% of men without the condition. Research on psoriatic arthritis has found a similar trend, with an estimated 45% higher risk of ED compared to men without the disease.
Chronic inflammation damages blood vessels over time, and the same vascular dysfunction that drives joint destruction can impair blood flow to the penis. Pain, stiffness, and reduced physical activity all further erode sexual function. So if you developed ED after starting methotrexate, the medication could be responsible, but the disease itself is also a plausible explanation, or the two may be working together.
Fatigue, Depression, and Desire
Methotrexate’s indirect effects on sexual health deserve attention too. Fatigue is one of the drug’s most common side effects, and chronic fatigue alone can significantly reduce sexual interest. Depression is also highly prevalent among people with rheumatoid arthritis and similar conditions, and it independently suppresses libido and erectile function. Loneliness and social withdrawal, which often accompany chronic illness, add another layer. Pain on methotrexate days (many people feel wiped out for a day or two after their weekly dose) can create a pattern where sex feels like an afterthought. These psychological and physical factors can be just as powerful as any hormonal disruption.
Low Dose vs. High Dose
Methotrexate dosing varies enormously depending on the condition being treated. For rheumatoid arthritis or psoriasis, typical weekly doses range from about 7.5 to 25 milligrams. For certain cancers, doses can be hundreds or even thousands of milligrams. The reproductive and hormonal effects of methotrexate, including reduced testosterone and testicular damage, have been documented more clearly at higher doses. If you’re on a standard low-dose regimen for an autoimmune condition, your risk of direct hormonal disruption is lower than what the most alarming studies describe, though it is not zero. The lab evidence on nitric oxide suppression, for instance, showed a clear dose-response relationship: more drug, more suppression.
Is It Reversible?
The hormonal changes methotrexate causes, including reduced testosterone and elevated FSH, suggest testicular function is being suppressed rather than permanently destroyed in most cases. Sperm production typically recovers after stopping the drug, though the timeline varies. The FDA label advises men of reproductive potential that low sperm counts can persist for some time after stopping treatment. For erectile function specifically, there is limited data on recovery timelines, but because the mechanisms involve suppression rather than irreversible tissue damage (at standard rheumatology doses), improvement after discontinuation is plausible.
What You Can Do
If you’ve noticed erectile changes since starting methotrexate, the first useful step is tracking whether the problem correlates with your dosing schedule. Many people take methotrexate once weekly and feel their worst side effects for one to two days afterward. If your difficulties cluster around those days, the link becomes more suggestive.
Ensuring adequate zinc intake is a reasonable, low-risk measure. Methotrexate depletes zinc, and zinc is required for healthy testosterone production. Most people on methotrexate already take folic acid to counteract other side effects, but zinc is not routinely supplemented despite evidence that it protects reproductive tissue from methotrexate-related damage. Staying physically active, managing fatigue, and addressing any depression are equally important, since these indirect pathways can be just as disruptive as the hormonal ones. A blood test checking testosterone, FSH, and prolactin levels can help clarify whether the drug is directly affecting your hormones or whether other factors are more likely driving the problem.