Can high blood sugar levels affect men's sexual performance? Science says so.

Metabolic health factors, including small increases in blood sugar, are the main drivers of changes in the reproductive system and sexual functioning of aging men , according to a study presented Saturday at ENDO 2025, the Endocrine Society's annual meeting in San Francisco, California.

The Endocrine Society is the world's oldest and largest organization of scientists dedicated to hormone research and physicians who care for people with hormone-related diseases. It has more than 18,000 members, including scientists, physicians, educators, nurses, and students from 122 countries.

"Although age and testosterone levels have long been considered a driver of declining sexual health in men, our research indicates that these changes correlate more closely with modest increases in blood sugar and other metabolic changes," said Michael Zitzmann, MD, Ph.D., professor and medical doctor at the University Hospital of Muenster, Germany. "This means men can take steps to preserve or restore their reproductive health with appropriate lifestyle choices and medical interventions."

These findings follow a long-term study of healthy men (without diabetes mellitus, heart disease, and/or cancer) aged 18 to 85, which began in 2014 with 200 participants and concluded in 2020 with 117. Researchers studied progressive changes in the participants' semen and hormonal profiles, erectile function, and metabolic health (BMI and blood sugar levels as measured by the HbA1c test).

The results indicated that, over time, hormone levels and semen parameters remained largely within normal ranges. However, sperm movement and erectile function decreased in men with minimally elevated blood sugar levels that were below the diabetes threshold of 6.5% HbA1c .

The study also found that while testosterone levels did not directly impact erectile function, they did correlate with participants' assessment of their libido.

"We hope the information gained from this study will help physicians and their patients develop effective plans for maintaining male sexual health," Zitzmann added. " We now know that it is within our power to maintain men's sexual and reproductive well-being, even as they age ."

With information from the Endocrine Society