Does metformin cause erectile dysfunction (ED)?

Metformin, a common medication for type 2 diabetes, hasn't been shown to directly cause erectile dysfunction (ED), though research on the link is mixed. It may affect testosterone levels, which play a role in erections, and diabetes itself is a known risk factor for ED. Here's what research says about the relationship between metformin and ED, and what may help.

Can metformin cause ED? Metformin hasn't been shown to directly cause erectile dysfunction, but research is mixed. Some studies link it to lower testosterone levels, which may contribute to ED, while others suggest it may support erectile function.

According to one small study, men with type 2 diabetes who took metformin had lower testosterone levels and sex drive than those who took another diabetes medication. Since low testosterone can affect sexual desire and erectile function, this could contribute to ED in some people. A case report also describes a man whose ED began after starting metformin and resolved after stopping it.

Another study of men with both type 2 diabetes and chronic kidney disease found that those who used metformin had higher odds of having ED. However, the study couldn't prove that metformin directly caused ED, and all participants had underlying conditions known to affect erectile function on their own.

On the other hand, some research suggests metformin may help improve erectile function by supporting blood vessel function and increasing nitric oxide availability, which promotes blood flow to the penis. More research is needed to confirm these effects.

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Diabetes can damage blood vessels and nerves and affect hormone levels, making the condition itself a well-established contributor to ED. In fact, up to 66% of men with type 2 diabetes also experience ED, and ED is at least three times more common in men with diabetes than in those without.

Over time, high blood sugar levels can damage nerves and blood vessels throughout the body, including in the penis. This can reduce blood flow and sexual sensation, making it difficult for people with diabetes to achieve and maintain a firm erection.

Diabetes can also affect testosterone levels, potentially due to insulin resistance. Lower testosterone levels are associated with more severe ED symptoms, suggesting hormonal changes may be another way diabetes contributes to ED.

For people with ED that may be related to diabetes or metformin, these strategies may help:

Talk to your healthcare provider

Talking with a healthcare provider is the first step to finding a solution. A healthcare provider can check testosterone levels, evaluate other potential causes of ED, and review whether metformin or another medication could be contributing.

The good news is that effective ED treatments are available, and a healthcare provider on Ro can help determine which may be appropriate.

Consider prescription medication for ED

Prescription medications known as phosphodiesterase type 5 (PDE5) inhibitors work by increasing blood flow to the penis, which can make it easier to achieve and maintain an erection for satisfactory sexual activity. Popular PDE5 inhibitors (all of which are oral medications) include:

• Viagra (sildenafil)

• Cialis (tadalafil)

• Vardenafil (formerly sold under the brand names Levitra and Staxyn)

• Stendra (avanafil)

Not a fan of swallowing pills? Alternative formulations include sublingual (under the tongue) options such as Ro Sparks, which contains tadalafil and sildenafil for fast-acting results. Another pill-free option is Ro's Daily Rise Gummies; each fruit-flavored gummy contains 7 mg of tadalafil. Both are compounded medications, which means they aren't approved by the US Food and Drug Administration (FDA) or reviewed by the FDA for safety, quality, or effectiveness.

Exercise regularly

Consistent physical activity may help improve ED and overall sexual health. That's because exercise can boost cardiovascular health and increase the production of nitric oxide — both of which can help improve blood flow to the penis, promoting erections.

For people new to exercise or returning after a break, regular aerobic activities such as walking, running, or swimming can be a simple way to start. It is recommended to aim for at least 150 minutes of moderate aerobic exercise weekly.

Eat a healthy, balanced diet 

Following a healthy diet may help improve ED by supporting blood sugar control and cardiovascular health. Research suggests that a Mediterranean-style eating plan, which focuses on whole foods such as fruits, vegetables, whole grains, lean proteins, and healthy fats, is associated with a lower risk of ED.

A heart-healthy diet rich in fruits, vegetables, whole grains, nuts, and fish may also support the vascular health involved in erectile function.

Prioritize sufficient sleep

 Getting enough shut-eye is essential for physical and mental health and can also affect sexual function. 

Testosterone levels naturally increase during sleep, peaking around the first episode of rapid eye movement (REM) sleep. Research suggests losing sleep, especially in the second half of the night, can lower testosterone the next morning.

Try to get 7–9 hours of quality sleep each night. Smart sleep hygiene habits can help, such as creating a relaxing sleep environment, following a consistent sleep schedule, and avoiding electronics, caffeine, and alcohol close to bedtime.

Metformin is generally safe and well-tolerated, but, like any other medication, it can cause side effects in some people, particularly at the onset of treatment. Symptoms tend to subside over time as the body adjusts to the medication, and taking metformin with food may help reduce or prevent side effects.

Common metformin side effects include: 

• Diarrhea 

• Nausea

• Vomiting 

• Abdominal pain 

• Indigestion

• Bloating 

• Loss of appetite 

Less common but more serious side effects include: 

• Lactic acidosis. This is a rare but potentially fatal condition in which lactic acid builds up in the bloodstream. Symptoms can be nonspecific and may include feeling very weak or unwell, muscle pain, trouble breathing, unusual sleepiness, or abdominal discomfort.

• Vitamin B12 deficiency. Long-term use (around 4–5 years, according to research) of metformin can interfere with the body's absorption of vitamin B12, potentially leading to a deficiency. 

• Hypoglycemia. Though rare, metformin can sometimes cause hypoglycemia (dangerously low blood sugar levels), especially when combined with other glucose-lowering medications or conditions. Symptoms of hypoglycemia can include sweating, shakiness, weakness, dizziness, hunger, a fast heartbeat, and confusion.

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Metformin is a commonly prescribed medication for type 2 diabetes. So, does metformin cause ED? Here's what we know:

• Metformin hasn't been shown to directly cause ED. However, some research suggests it may lower testosterone levels, which can contribute to ED, while other studies suggest it may support erectile function.

• Diabetes itself is a well-established contributor to ED. High blood sugar can damage blood vessels and nerves involved in erections, while diabetes may also contribute to low testosterone.

• ED is treatable, whether or not a person takes metformin. Lifestyle changes and prescription medications such as Viagra (sildenafil) or Cialis (tadalafil) may help improve erectile function.