Erectile dysfunction (ED) is a man’s inability to achieve or maintain an erection suitable for satisfactory sex.

To understand ED, it’s important to understand how erections occur. When a man is sexually aroused, nerves and chemicals work together to relax smooth muscle tissue and widen arteries so that the penis can fill with blood. Veins constrict to keep the blood inside the penis, forming the erection. Once the man ejaculates, the blood is released back into the body.

ED becomes more common as men get older. It’s also associated with some medical conditions, like heart disease and diabetes. In fact, an estimated 50% of diabetic men have some degree of ED.